From 2a39beedd2d621212c04f6952aec58385d46c97f Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Thu, 28 Jul 2022 17:35:43 +0300
Subject: [PATCH 01/40] Use Enum class as single source of directive names

---
 src/Directives.php                   | 24 ++++++++++++++----------
 src/Directives/ExternalDirective.php |  7 +++----
 src/Directives/KeyDirective.php      |  3 ++-
 src/Directives/ProvidesDirective.php |  3 ++-
 src/Directives/RequiresDirective.php |  3 ++-
 src/Enum/DirectiveEnum.php           | 26 ++++++++++++++++++++++++++
 src/Utils/FederatedSchemaPrinter.php |  3 ++-
 7 files changed, 51 insertions(+), 18 deletions(-)
 create mode 100644 src/Enum/DirectiveEnum.php

diff --git a/src/Directives.php b/src/Directives.php
index 8e71aa6..8ee46ca 100644
--- a/src/Directives.php
+++ b/src/Directives.php
@@ -8,21 +8,23 @@
 use Apollo\Federation\Directives\ExternalDirective;
 use Apollo\Federation\Directives\ProvidesDirective;
 use Apollo\Federation\Directives\RequiresDirective;
+use Apollo\Federation\Enum\DirectiveEnum;
+use GraphQL\Type\Definition\Directive;
 
 /**
  * Helper class to get directives for annotating federated entity types.
  */
 class Directives
 {
-    /** @var array */
-    private static $directives;
+    /** @var array<string,Directive> */
+    private static $directives = null;
 
     /**
      * Gets the @key directive
      */
     public static function key(): KeyDirective
     {
-        return self::getDirectives()['key'];
+        return self::getDirectives()[DirectiveEnum::KEY];
     }
 
     /**
@@ -30,7 +32,7 @@ public static function key(): KeyDirective
      */
     public static function external(): ExternalDirective
     {
-        return self::getDirectives()['external'];
+        return self::getDirectives()[DirectiveEnum::EXTERNAL];
     }
 
     /**
@@ -38,7 +40,7 @@ public static function external(): ExternalDirective
      */
     public static function requires(): RequiresDirective
     {
-        return self::getDirectives()['requires'];
+        return self::getDirectives()[DirectiveEnum::REQUIRES];
     }
 
     /**
@@ -46,20 +48,22 @@ public static function requires(): RequiresDirective
      */
     public static function provides(): ProvidesDirective
     {
-        return self::getDirectives()['provides'];
+        return self::getDirectives()[DirectiveEnum::PROVIDES];
     }
 
     /**
      * Gets the directives that can be used on federated entity types
+     *
+     * @return array<string,Directive>
      */
     public static function getDirectives(): array
     {
         if (!self::$directives) {
             self::$directives = [
-                'key' => new KeyDirective(),
-                'external' => new ExternalDirective(),
-                'requires' => new RequiresDirective(),
-                'provides' => new ProvidesDirective()
+                DirectiveEnum::KEY => new KeyDirective(),
+                DirectiveEnum::EXTERNAL => new ExternalDirective(),
+                DirectiveEnum::REQUIRES => new RequiresDirective(),
+                DirectiveEnum::PROVIDES => new ProvidesDirective(),
             ];
         }
 
diff --git a/src/Directives/ExternalDirective.php b/src/Directives/ExternalDirective.php
index afd7181..7a837b5 100644
--- a/src/Directives/ExternalDirective.php
+++ b/src/Directives/ExternalDirective.php
@@ -2,10 +2,9 @@
 
 namespace Apollo\Federation\Directives;
 
-use GraphQL\Type\Definition\Type;
-use GraphQL\Type\Definition\Directive;
-use GraphQL\Type\Definition\FieldArgument;
+use Apollo\Federation\Enum\DirectiveEnum;
 use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Directive;
 
 /**
  * The `@external` directive is used to mark a field as owned by another service. This
@@ -17,7 +16,7 @@ class ExternalDirective extends Directive
     public function __construct()
     {
         parent::__construct([
-            'name' => 'external',
+            'name' => DirectiveEnum::EXTERNAL,
             'locations' => [DirectiveLocation::FIELD_DEFINITION]
         ]);
     }
diff --git a/src/Directives/KeyDirective.php b/src/Directives/KeyDirective.php
index 72469aa..08623d8 100644
--- a/src/Directives/KeyDirective.php
+++ b/src/Directives/KeyDirective.php
@@ -2,6 +2,7 @@
 
 namespace Apollo\Federation\Directives;
 
+use Apollo\Federation\Enum\DirectiveEnum;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
@@ -16,7 +17,7 @@ class KeyDirective extends Directive
     public function __construct()
     {
         parent::__construct([
-            'name' => 'key',
+            'name' => DirectiveEnum::KEY,
             'locations' => [DirectiveLocation::OBJECT, DirectiveLocation::IFACE],
             'args' => [
                 new FieldArgument([
diff --git a/src/Directives/ProvidesDirective.php b/src/Directives/ProvidesDirective.php
index f33b603..f474cae 100644
--- a/src/Directives/ProvidesDirective.php
+++ b/src/Directives/ProvidesDirective.php
@@ -2,6 +2,7 @@
 
 namespace Apollo\Federation\Directives;
 
+use Apollo\Federation\Enum\DirectiveEnum;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
@@ -16,7 +17,7 @@ class ProvidesDirective extends Directive
     public function __construct()
     {
         parent::__construct([
-            'name' => 'provides',
+            'name' => DirectiveEnum::PROVIDES,
             'locations' => [DirectiveLocation::FIELD_DEFINITION],
             'args' => [
                 new FieldArgument([
diff --git a/src/Directives/RequiresDirective.php b/src/Directives/RequiresDirective.php
index 6583407..ab8d9e7 100644
--- a/src/Directives/RequiresDirective.php
+++ b/src/Directives/RequiresDirective.php
@@ -2,6 +2,7 @@
 
 namespace Apollo\Federation\Directives;
 
+use Apollo\Federation\Enum\DirectiveEnum;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
@@ -17,7 +18,7 @@ class RequiresDirective extends Directive
     public function __construct()
     {
         parent::__construct([
-            'name' => 'requires',
+            'name' => DirectiveEnum::REQUIRES,
             'locations' => [DirectiveLocation::FIELD_DEFINITION],
             'args' => [
                 new FieldArgument([
diff --git a/src/Enum/DirectiveEnum.php b/src/Enum/DirectiveEnum.php
new file mode 100644
index 0000000..97ef22b
--- /dev/null
+++ b/src/Enum/DirectiveEnum.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Enum;
+
+class DirectiveEnum
+{
+    public const EXTERNAL = 'external';
+    public const KEY = 'key';
+    public const PROVIDES = 'provides';
+    public const REQUIRES = 'requires';
+
+    /**
+     * @return string[]
+     */
+    public static function getAll(): array
+    {
+        return [self::EXTERNAL, self::KEY, self::PROVIDES, self::REQUIRES];
+    }
+
+    private function __construct()
+    {
+        // forbid creation of an object
+    }
+}
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 8eab202..bdce6ff 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -32,6 +32,7 @@
 
 namespace Apollo\Federation\Utils;
 
+use Apollo\Federation\Enum\DirectiveEnum;
 use GraphQL\Error\Error;
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
@@ -97,7 +98,7 @@ static function ($type) {
 
     public static function isFederatedDirective($type): bool
     {
-        return in_array($type->name, ['key', 'provides', 'requires', 'external']);
+        return \in_array($type->name, DirectiveEnum::getAll());
     }
 
     /**

From c0ff092bf3f79fe93cf03dfdc20fd430b81b3711 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 29 Jul 2022 07:53:33 +0300
Subject: [PATCH 02/40] Use constants as single source of entity config options
 names

---
 src/Types/EntityObjectType.php       | 26 ++++++++++++++++----------
 src/Utils/FederatedSchemaPrinter.php | 14 ++++++++------
 2 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index f2e70ad..fe6c421 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -7,28 +7,27 @@
 use GraphQL\Utils\Utils;
 use GraphQL\Type\Definition\ObjectType;
 
-use array_key_exists;
-
 /**
  * An entity is a type that can be referenced by another service. Entities create
  * connection points between services and form the basic building blocks of a federated
  * graph. Entities have a primary key whose value uniquely identifies a specific instance
  * of the type, similar to the function of a primary key in a SQL table
- * (see [related docs](https://www.apollographql.com/docs/apollo-server/federation/core-concepts/#entities-and-keys)).
+ * {@see https://www.apollographql.com/docs/apollo-server/federation/core-concepts/#entities-and-keys }.
  *
  * The `keyFields` property is required in the configuration, indicating the fields that
  * serve as the unique keys or identifiers of the entity.
  *
  * Sample usage:
- *
+ * <code>
  *     $userType = new Apollo\Federation\Types\EntityObjectType([
  *       'name' => 'User',
  *       'keyFields' => ['id', 'email'],
  *       'fields' => [...]
  *     ]);
+ * </code>
  *
  * Entity types can also set attributes to its fields to hint the gateway on how to resolve them.
- *
+ * <code>
  *     $userType = new Apollo\Federation\Types\EntityObjectType([
  *       'name' => 'User',
  *       'keyFields' => ['id', 'email'],
@@ -39,10 +38,17 @@
  *         ]
  *       ]
  *     ]);
- *
+ * </code>
  */
 class EntityObjectType extends ObjectType
 {
+    public const FIELD_KEY_FIELDS = 'keyFields';
+    public const FIELD_REFERENCE_RESOLVER = '__resolveReference';
+
+    public const FIELD_DIRECTIVE_IS_EXTERNAL = 'isExternal';
+    public const FIELD_DIRECTIVE_PROVIDES = 'provides';
+    public const FIELD_DIRECTIVE_REQUIRES = 'requires';
+
     /** @var array */
     private $keyFields;
 
@@ -54,11 +60,11 @@ class EntityObjectType extends ObjectType
      */
     public function __construct(array $config)
     {
-        $this->keyFields = $config['keyFields'];
+        $this->keyFields = $config[self::FIELD_KEY_FIELDS];
 
-        if (isset($config['__resolveReference'])) {
+        if (isset($config[self::FIELD_REFERENCE_RESOLVER])) {
             self::validateResolveReference($config);
-            $this->referenceResolver = $config['__resolveReference'];
+            $this->referenceResolver = $config[self::FIELD_REFERENCE_RESOLVER];
         }
 
         parent::__construct($config);
@@ -113,6 +119,6 @@ private function validateReferenceKeys($ref)
 
     public static function validateResolveReference(array $config)
     {
-        Utils::invariant(is_callable($config['__resolveReference']), 'Reference resolver has to be callable.');
+        Utils::invariant(is_callable($config[self::FIELD_REFERENCE_RESOLVER]), 'Reference resolver has to be callable.');
     }
 }
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index bdce6ff..5faa2ee 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -462,16 +462,18 @@ private static function printFieldFederatedDirectives($field)
     {
         $directives = [];
 
-        if (isset($field->config['isExternal']) && $field->config['isExternal'] === true) {
-            array_push($directives, '@external');
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL])
+            && $field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL] === true
+        ) {
+            $directives[] = '@external';
         }
 
-        if (isset($field->config['provides'])) {
-            array_push($directives, sprintf('@provides(fields: "%s")', $field->config['provides']));
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES])) {
+            $directives[] = sprintf('@provides(fields: "%s")', $field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]);
         }
 
-        if (isset($field->config['requires'])) {
-            array_push($directives, sprintf('@requires(fields: "%s")', $field->config['requires']));
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES])) {
+            $directives[] = sprintf('@requires(fields: "%s")', $field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]);
         }
 
         return implode(' ', $directives);

From 68ec4c503def2a22a138bc145096222f8ec2e8b8 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 29 Jul 2022 11:12:26 +0300
Subject: [PATCH 03/40] Fix code style

---
 src/Types/EntityObjectType.php       | 39 ++++++++-----
 src/Utils/FederatedSchemaPrinter.php | 87 +++++++++++++++++++---------
 2 files changed, 85 insertions(+), 41 deletions(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index fe6c421..fd617c4 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -4,8 +4,8 @@
 
 namespace Apollo\Federation\Types;
 
-use GraphQL\Utils\Utils;
 use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Utils\Utils;
 
 /**
  * An entity is a type that can be referenced by another service. Entities create
@@ -52,8 +52,8 @@ class EntityObjectType extends ObjectType
     /** @var array */
     private $keyFields;
 
-    /** @var callable */
-    public $referenceResolver;
+    /** @var callable|null */
+    public $referenceResolver = null;
 
     /**
      * @param mixed[] $config
@@ -81,9 +81,7 @@ public function getKeyFields(): array
     }
 
     /**
-     * Gets whether this entity has a resolver set
-     *
-     * @return bool
+     * Gets whether this entity has a resolver set.
      */
     public function hasReferenceResolver(): bool
     {
@@ -91,34 +89,47 @@ public function hasReferenceResolver(): bool
     }
 
     /**
-     * Resolves an entity from a reference
+     * Resolves an entity from a reference.
      *
-     * @param mixed $ref
-     * @param mixed $context
-     * @param mixed $info
+     * @param mixed|null $ref
+     * @param mixed|null $context
+     * @param mixed|null $info
+     *
+     * @retrun mixed|null
      */
     public function resolveReference($ref, $context = null, $info = null)
     {
         $this->validateReferenceResolver();
         $this->validateReferenceKeys($ref);
 
-        $entity = ($this->referenceResolver)($ref, $context, $info);
-        
-        return $entity;
+        return ($this->referenceResolver)($ref, $context, $info);
     }
 
+    /**
+     * @return void
+     */
     private function validateReferenceResolver()
     {
         Utils::invariant(isset($this->referenceResolver), 'No reference resolver was set in the configuration.');
     }
 
+    /**
+     * @param array{ __typename: mixed } $ref
+     *
+     * @return void
+     */
     private function validateReferenceKeys($ref)
     {
         Utils::invariant(isset($ref['__typename']), 'Type name must be provided in the reference.');
     }
 
+    /**
+     * @param array{ __resolveReference: mixed } $config
+     *
+     * @return void
+     */
     public static function validateResolveReference(array $config)
     {
-        Utils::invariant(is_callable($config[self::FIELD_REFERENCE_RESOLVER]), 'Reference resolver has to be callable.');
+        Utils::invariant(\is_callable($config[self::FIELD_REFERENCE_RESOLVER]), 'Reference resolver has to be callable.');
     }
 }
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 5faa2ee..d2ad466 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -37,11 +37,16 @@
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\EnumType;
+use GraphQL\Type\Definition\EnumValueDefinition;
+use GraphQL\Type\Definition\FieldArgument;
+use GraphQL\Type\Definition\FieldDefinition;
+use GraphQL\Type\Definition\InputObjectField;
 use GraphQL\Type\Definition\InputObjectType;
 use GraphQL\Type\Definition\InterfaceType;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\ScalarType;
 use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Definition\TypeWithFields;
 use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Introspection;
 use GraphQL\Type\Schema;
@@ -86,27 +91,27 @@ public static function doPrint(Schema $schema, array $options = []): string
     {
         return self::printFilteredSchema(
             $schema,
-            static function ($type) {
+            static function (Directive $type): bool {
                 return !Directive::isSpecifiedDirective($type) && !self::isFederatedDirective($type);
             },
-            static function ($type) {
+            static function (Type $type): bool {
                 return !Type::isBuiltInType($type);
             },
             $options
         );
     }
 
-    public static function isFederatedDirective($type): bool
+    public static function isFederatedDirective(Directive $type): bool
     {
-        return \in_array($type->name, DirectiveEnum::getAll());
+        return \in_array($type->name, DirectiveEnum::getAll(), true);
     }
 
     /**
      * @param bool[] $options
      */
-    private static function printFilteredSchema(Schema $schema, $directiveFilter, $typeFilter, $options): string
+    private static function printFilteredSchema(Schema $schema, callable $directiveFilter, callable $typeFilter, array $options): string
     {
-        $directives = array_filter($schema->getDirectives(), static function ($directive) use ($directiveFilter) {
+        $directives = array_filter($schema->getDirectives(), static function (Directive $directive) use ($directiveFilter): bool {
             return $directiveFilter($directive);
         });
 
@@ -120,10 +125,10 @@ private static function printFilteredSchema(Schema $schema, $directiveFilter, $t
                 "\n\n",
                 array_filter(
                     array_merge(
-                        array_map(static function ($directive) use ($options) {
+                        array_map(static function (Directive $directive) use ($options) {
                             return self::printDirective($directive, $options);
                         }, $directives),
-                        array_map(static function ($type) use ($options) {
+                        array_map(static function (Type $type) use ($options) {
                             return self::printType($type, $options);
                         }, $types)
                     )
@@ -132,7 +137,10 @@ private static function printFilteredSchema(Schema $schema, $directiveFilter, $t
         );
     }
 
-    private static function printDirective($directive, $options): string
+    /**
+     * @param bool[] $options
+     */
+    private static function printDirective(Directive $directive, array $options): string
     {
         return self::printDescription($options, $directive) .
             'directive @' .
@@ -142,7 +150,11 @@ private static function printDirective($directive, $options): string
             implode(' | ', $directive->locations);
     }
 
-    private static function printDescription($options, $def, $indentation = '', $firstInBlock = true): string
+    /**
+     * @param bool[] $options
+     * @param Directive|EnumValueDefinition|FieldArgument|Type|object $def
+     */
+    private static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
     {
         if (!$def->description) {
             return '';
@@ -162,13 +174,13 @@ private static function printDescription($options, $def, $indentation = '', $fir
         }
 
         // Format a multi-line block quote to account for leading space.
-        $hasLeadingSpace = isset($lines[0]) && (substr($lines[0], 0, 1) === ' ' || substr($lines[0], 0, 1) === '\t');
+        $hasLeadingSpace = isset($lines[0]) && \in_array(substr($lines[0], 0, 1), [' ', '\t'], true);
 
         if (!$hasLeadingSpace) {
             $description .= "\n";
         }
 
-        $lineLength = count($lines);
+        $lineLength = \count($lines);
 
         for ($i = 0; $i < $lineLength; $i++) {
             if ($i !== 0 || !$hasLeadingSpace) {
@@ -223,7 +235,10 @@ private static function breakLine(string $line, int $maxLen): array
         return array_map('trim', $parts);
     }
 
-    private static function printDescriptionWithComments($lines, $indentation, $firstInBlock): string
+    /**
+     * @param string[] $lines
+     */
+    private static function printDescriptionWithComments(array $lines, string $indentation, bool $firstInBlock): string
     {
         $description = $indentation && !$firstInBlock ? "\n" : '';
 
@@ -238,12 +253,16 @@ private static function printDescriptionWithComments($lines, $indentation, $firs
         return $description;
     }
 
-    private static function escapeQuote($line): string
+    private static function escapeQuote(string $line): string
     {
         return str_replace('"""', '\\"""', $line);
     }
 
-    private static function printArgs($options, $args, $indentation = ''): string
+    /**
+     * @param bool[]               $options
+     * @param FieldArgument[]|null $args
+     */
+    private static function printArgs(array $options, $args, string $indentation = ''): string
     {
         if (!$args) {
             return '';
@@ -263,7 +282,7 @@ private static function printArgs($options, $args, $indentation = ''): string
             implode(
                 "\n",
                 array_map(
-                    static function ($arg, $i) use ($indentation, $options) {
+                    static function (FieldArgument $arg, $i) use ($indentation, $options): string {
                         return self::printDescription($options, $arg, '  ' . $indentation, !$i) .
                             '  ' .
                             $indentation .
@@ -277,6 +296,9 @@ static function ($arg, $i) use ($indentation, $options) {
         );
     }
 
+    /**
+     * @param InputObjectField|FieldArgument $arg
+     */
     private static function printInputValue($arg): string
     {
         $argDecl = $arg->name . ': ' . (string) $arg->getType();
@@ -294,11 +316,12 @@ private static function printInputValue($arg): string
     public static function printType(Type $type, array $options = []): string
     {
         if ($type instanceof ScalarType) {
+            // TODO: use constant instead of magic scalar value
             if ($type->name !== '_Any') {
                 return self::printScalar($type, $options);
-            } else {
-                return '';
             }
+
+            return '';
         }
 
         if ($type instanceof EntityObjectType || $type instanceof EntityRefObjectType) {
@@ -306,11 +329,12 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof ObjectType) {
+            // TODO: use constant instead of magic scalar value
             if ($type->name !== '_Service') {
                 return self::printObject($type, $options);
-            } else {
-                return '';
             }
+
+            return '';
         }
 
         if ($type instanceof InterfaceType) {
@@ -318,11 +342,12 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof UnionType) {
+            // TODO: use constant instead of magic scalar value
             if ($type->name !== '_Entity') {
                 return self::printUnion($type, $options);
-            } else {
-                return '';
             }
+
+            return '';
         }
 
         if ($type instanceof EnumType) {
@@ -364,6 +389,7 @@ private static function printObject(ObjectType $type, array $options): string
                 )
             : '';
 
+        // FIXME: hardcoded names! They can be different in real.
         $queryExtends = $type->name === 'Query' || $type->name === 'Mutation' ? 'extend ' : '';
 
         return self::printDescription($options, $type) .
@@ -414,13 +440,16 @@ private static function printEntityObject(EntityObjectType $type, array $options
 
     /**
      * @param bool[] $options
+     * @param EntityObjectType|InterfaceType|ObjectType $type
      */
-    private static function printFields($options, $type): string
+    private static function printFields(array $options, TypeWithFields $type): string
     {
         $fields = array_values($type->getFields());
 
+        // FIXME it looks like hardcoded name. Potentially, it can be different!
         if ($type->name === 'Query') {
-            $fields = array_filter($fields, function ($field) {
+            $fields = array_filter($fields, static function (FieldDefinition $field): bool {
+                //TODO use constants instead of magic scalar values
                 return $field->name !== '_service' && $field->name !== '_entities';
             });
         }
@@ -428,7 +457,7 @@ private static function printFields($options, $type): string
         return implode(
             "\n",
             array_map(
-                static function ($f, $i) use ($options) {
+                static function (FieldDefinition $f, $i) use ($options) {
                     return self::printDescription($options, $f, '  ', !$i) .
                         '  ' .
                         $f->name .
@@ -445,6 +474,9 @@ static function ($f, $i) use ($options) {
         );
     }
 
+    /**
+     * @param EnumValueDefinition|FieldDefinition $fieldOrEnumVal
+     */
     private static function printDeprecated($fieldOrEnumVal): string
     {
         $reason = $fieldOrEnumVal->deprecationReason;
@@ -458,7 +490,7 @@ private static function printDeprecated($fieldOrEnumVal): string
         return ' @deprecated(reason: ' . Printer::doPrint(AST::astFromValue($reason, Type::string())) . ')';
     }
 
-    private static function printFieldFederatedDirectives($field)
+    private static function printFieldFederatedDirectives(FieldDefinition $field): string
     {
         $directives = [];
 
@@ -507,9 +539,10 @@ private static function printEnum(EnumType $type, array $options): string
     }
 
     /**
+     * @param EnumValueDefinition[] $values
      * @param bool[] $options
      */
-    private static function printEnumValues($values, $options): string
+    private static function printEnumValues(array $values, array $options): string
     {
         return implode(
             "\n",

From 90231df42ab401c498f25ad028b5bf13a6ecf5af Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 29 Jul 2022 11:22:38 +0300
Subject: [PATCH 04/40] Create TypeEnum as single source of type names

---
 src/Enum/TypeEnum.php                | 25 +++++++++++++++++++++++++
 src/FederatedSchema.php              |  7 ++++---
 src/Utils/FederatedSchemaPrinter.php | 16 +++++++---------
 3 files changed, 36 insertions(+), 12 deletions(-)
 create mode 100644 src/Enum/TypeEnum.php

diff --git a/src/Enum/TypeEnum.php b/src/Enum/TypeEnum.php
new file mode 100644
index 0000000..0cbacbd
--- /dev/null
+++ b/src/Enum/TypeEnum.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Enum;
+
+final class TypeEnum
+{
+    public const ANY = '_Any';
+    public const ENTITY = '_Entity';
+    public const SERVICE = '_Service';
+
+    /**
+     * @return string[]
+     */
+    public static function getAll(): array
+    {
+        return [self::ANY, self::ENTITY, self::SERVICE];
+    }
+
+    private function __construct()
+    {
+        // forbid creation of an object
+    }
+}
diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 1704d07..7b70cd8 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -4,6 +4,7 @@
 
 namespace Apollo\Federation;
 
+use Apollo\Federation\Enum\TypeEnum;
 use GraphQL\Type\Schema;
 use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\ObjectType;
@@ -124,7 +125,7 @@ private function getQueryTypeConfig(array $config): array
     private function getQueryTypeServiceFieldConfig(): array
     {
         $serviceType = new ObjectType([
-            'name' => '_Service',
+            'name' => TypeEnum::SERVICE,
             'fields' => [
                 'sdl' => [
                     'type' => Type::string(),
@@ -153,12 +154,12 @@ private function getQueryTypeEntitiesFieldConfig(?array $config): array
         }
 
         $entityType = new UnionType([
-            'name' => '_Entity',
+            'name' => TypeEnum::ENTITY,
             'types' => array_values($this->getEntityTypes())
         ]);
 
         $anyType = new CustomScalarType([
-            'name' => '_Any',
+            'name' => TypeEnum::ANY,
             'serialize' => function ($value) {
                 return $value;
             }
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index d2ad466..6e44ba8 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -33,6 +33,10 @@
 namespace Apollo\Federation\Utils;
 
 use Apollo\Federation\Enum\DirectiveEnum;
+use Apollo\Federation\Enum\TypeEnum;
+use Apollo\Federation\Types\EntityObjectType;
+use Apollo\Federation\Types\EntityRefObjectType;
+
 use GraphQL\Error\Error;
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
@@ -53,9 +57,6 @@
 use GraphQL\Utils\AST;
 use GraphQL\Utils\Utils;
 
-use Apollo\Federation\Types\EntityObjectType;
-use Apollo\Federation\Types\EntityRefObjectType;
-
 use function array_filter;
 use function array_keys;
 use function array_map;
@@ -316,8 +317,7 @@ private static function printInputValue($arg): string
     public static function printType(Type $type, array $options = []): string
     {
         if ($type instanceof ScalarType) {
-            // TODO: use constant instead of magic scalar value
-            if ($type->name !== '_Any') {
+            if ($type->name !== TypeEnum::ANY) {
                 return self::printScalar($type, $options);
             }
 
@@ -329,8 +329,7 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof ObjectType) {
-            // TODO: use constant instead of magic scalar value
-            if ($type->name !== '_Service') {
+            if (TypeEnum::SERVICE !== $type->name) {
                 return self::printObject($type, $options);
             }
 
@@ -342,8 +341,7 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof UnionType) {
-            // TODO: use constant instead of magic scalar value
-            if ($type->name !== '_Entity') {
+            if (TypeEnum::ENTITY !== $type->name) {
                 return self::printUnion($type, $options);
             }
 

From 9af5719170a85f5b1f8ac31490aff9aba9dd7016 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 29 Jul 2022 11:35:26 +0300
Subject: [PATCH 05/40] Fix code style

---
 src/FederatedSchema.php | 86 +++++++++++++++++++++++------------------
 1 file changed, 49 insertions(+), 37 deletions(-)

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 7b70cd8..6e9970d 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -5,19 +5,19 @@
 namespace Apollo\Federation;
 
 use Apollo\Federation\Enum\TypeEnum;
-use GraphQL\Type\Schema;
+use Apollo\Federation\Types\EntityObjectType;
+use Apollo\Federation\Utils\FederatedSchemaPrinter;
 use GraphQL\Type\Definition\CustomScalarType;
+use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\ObjectType;
-use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Definition\UnionType;
+use GraphQL\Type\Schema;
 use GraphQL\Utils\TypeInfo;
 use GraphQL\Utils\Utils;
 
-use Apollo\Federation\Types\EntityObjectType;
-use Apollo\Federation\Utils\FederatedSchemaPrinter;
-
 /**
- * A federated GraphQL schema definition (see [related docs](https://www.apollographql.com/docs/apollo-server/federation/introduction))
+ * A federated GraphQL schema definition {@see https://www.apollographql.com/docs/apollo-server/federation/introduction }.
  *
  * A federated schema defines a self-contained GraphQL service that can be merged with
  * other services by the [Apollo Gateway](https://www.apollographql.com/docs/intro/platform/#gateway)
@@ -27,7 +27,7 @@
  * directives to hint the gateway on how entity types and references should be resolved.
  *
  * Usage example:
- *
+ * <code>
  *     $userType = new Apollo\Federation\Types\EntityObjectType([
  *       'name' => 'User',
  *       'fields' => [
@@ -52,6 +52,7 @@
  *     $schema = new Apollo\Federation\FederatedSchema([
  *       'query' => $queryType
  *     ]);
+ * </code>
  */
 class FederatedSchema extends Schema
 {
@@ -61,7 +62,10 @@ class FederatedSchema extends Schema
     /** @var Directive[] */
     protected $entityDirectives;
 
-    public function __construct($config)
+    /**
+     * @param array<string,mixed> $config
+     */
+    public function __construct(array $config)
     {
         $this->entityTypes = $this->extractEntityTypes($config);
         $this->entityDirectives = Directives::getDirectives();
@@ -72,7 +76,7 @@ public function __construct($config)
     }
 
     /**
-     * Returns all the resolved entity types in the schema
+     * Returns all the resolved entity types in the schema.
      *
      * @return EntityObjectType[]
      */
@@ -82,9 +86,7 @@ public function getEntityTypes(): array
     }
 
     /**
-     * Indicates whether the schema has entity types resolved
-     *
-     * @return bool
+     * Indicates whether the schema has entity types resolved.
      */
     public function hasEntityTypes(): bool
     {
@@ -102,11 +104,15 @@ private function getEntityDirectivesConfig(array $config): array
         return $config;
     }
 
-    /** @var array */
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return array{ query: ObjectType }
+     */
     private function getQueryTypeConfig(array $config): array
     {
         $queryTypeConfig = $config['query']->config;
-        if (is_callable($queryTypeConfig['fields'])) {
+        if (\is_callable($queryTypeConfig['fields'])) {
             $queryTypeConfig['fields'] = $queryTypeConfig['fields']();
         }
 
@@ -117,11 +123,13 @@ private function getQueryTypeConfig(array $config): array
         );
 
         return [
-            'query' => new ObjectType($queryTypeConfig)
+            'query' => new ObjectType($queryTypeConfig),
         ];
     }
 
-    /** @var array */
+    /**
+     * @return array{ _service: array<string,mixed> }
+     */
     private function getQueryTypeServiceFieldConfig(): array
     {
         $serviceType = new ObjectType([
@@ -131,9 +139,9 @@ private function getQueryTypeServiceFieldConfig(): array
                     'type' => Type::string(),
                     'resolve' => function () {
                         return FederatedSchemaPrinter::doPrint($this);
-                    }
-                ]
-            ]
+                    },
+                ],
+            ],
         ]);
 
         return [
@@ -141,12 +149,16 @@ private function getQueryTypeServiceFieldConfig(): array
                 'type' => Type::nonNull($serviceType),
                 'resolve' => function () {
                     return [];
-                }
-            ]
+                },
+            ],
         ];
     }
 
-    /** @var array */
+    /**
+     * @param array<string,mixed>|null $config
+     *
+     * @return array<string,mixed>
+     */
     private function getQueryTypeEntitiesFieldConfig(?array $config): array
     {
         if (!$this->hasEntityTypes()) {
@@ -155,14 +167,14 @@ private function getQueryTypeEntitiesFieldConfig(?array $config): array
 
         $entityType = new UnionType([
             'name' => TypeEnum::ENTITY,
-            'types' => array_values($this->getEntityTypes())
+            'types' => array_values($this->getEntityTypes()),
         ]);
 
         $anyType = new CustomScalarType([
             'name' => TypeEnum::ANY,
             'serialize' => function ($value) {
                 return $value;
-            }
+            },
         ]);
 
         return [
@@ -170,23 +182,23 @@ private function getQueryTypeEntitiesFieldConfig(?array $config): array
                 'type' => Type::listOf($entityType),
                 'args' => [
                     'representations' => [
-                        'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType)))
-                    ]
+                        'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType))),
+                    ],
                 ],
                 'resolve' => function ($root, $args, $context, $info) use ($config) {
-                    if (isset($config) && isset($config['resolve']) && is_callable($config['resolve'])) {
-                        return $config['resolve']($root, $args, $context, $info);;
-                    } else {
-                        return $this->resolve($root, $args, $context, $info);
+                    if ($config && isset($config['resolve']) && \is_callable($config['resolve'])) {
+                        return $config['resolve']($root, $args, $context, $info);
                     }
-                }
-            ]
+
+                    return $this->resolve($root, $args, $context, $info);
+                },
+            ],
         ];
     }
 
-    private function resolve($root, $args, $context, $info)
+    private function resolve($root, $args, $context, $info): array
     {
-        return array_map(function ($ref) use ($context, $info) {
+        return array_map(static function ($ref) use ($context, $info) {
             Utils::invariant(isset($ref['__typename']), 'Type name must be provided in the reference.');
 
             $typeName = $ref['__typename'];
@@ -204,12 +216,12 @@ private function resolve($root, $args, $context, $info)
                 return $ref;
             }
 
-            $r = $type->resolveReference($ref, $context, $info);
-            return $r;
+            return $type->resolveReference($ref, $context, $info);
         }, $args['representations']);
     }
+
     /**
-     * @param array $config
+     * @param array<string,mixed> $config
      *
      * @return EntityObjectType[]
      */

From 877810b79fd114176c456810fe4476b07a988571 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 29 Jul 2022 12:57:59 +0300
Subject: [PATCH 06/40] Fix code style

---
 src/FederatedSchema.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 6e9970d..e1d16fc 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -9,6 +9,7 @@
 use Apollo\Federation\Utils\FederatedSchemaPrinter;
 use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\Directive;
+use GraphQL\Type\Definition\ListOfType;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\UnionType;
@@ -94,7 +95,9 @@ public function hasEntityTypes(): bool
     }
 
     /**
-     * @return Directive[]
+     * @param array<string,mixed> $config
+     *
+     * @return array<string,mixed>
      */
     private function getEntityDirectivesConfig(array $config): array
     {
@@ -157,7 +160,7 @@ private function getQueryTypeServiceFieldConfig(): array
     /**
      * @param array<string,mixed>|null $config
      *
-     * @return array<string,mixed>
+     * @return array<string,array{ type: ListOfType, args: array<string,array<string,Type>>, resolve: callable }>
      */
     private function getQueryTypeEntitiesFieldConfig(?array $config): array
     {

From 268eee6b629b4a64e0c342b6da2ca0564463abbd Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 13:28:04 +0300
Subject: [PATCH 07/40] Print simple and compound directives' argument "fields"

---
 src/Utils/FederatedSchemaPrinter.php | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 6e44ba8..369b3fd 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -419,7 +419,7 @@ private static function printEntityObject(EntityObjectType $type, array $options
         $keyDirective = '';
 
         foreach ($type->getKeyFields() as $keyField) {
-            $keyDirective = $keyDirective . sprintf(' @key(fields: "%s")', $keyField);
+            $keyDirective = $keyDirective . sprintf(' @key(fields: "%s")', self::printKeyFields($keyField));
         }
 
         $isEntityRef = $type instanceof EntityRefObjectType;
@@ -499,11 +499,11 @@ private static function printFieldFederatedDirectives(FieldDefinition $field): s
         }
 
         if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES])) {
-            $directives[] = sprintf('@provides(fields: "%s")', $field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]);
+            $directives[] = sprintf('@provides(fields: "%s")', self::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]));
         }
 
         if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES])) {
-            $directives[] = sprintf('@requires(fields: "%s")', $field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]);
+            $directives[] = sprintf('@requires(fields: "%s")', self::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]));
         }
 
         return implode(' ', $directives);
@@ -518,6 +518,28 @@ private static function printInterface(InterfaceType $type, array $options): str
             sprintf("interface %s {\n%s\n}", $type->name, self::printFields($options, $type));
     }
 
+    /**
+     * Print simple and compound primary key fields
+     * {@see https://www.apollographql.com/docs/federation/v1/entities#compound-primary-keys }.
+     *
+     * @param string|array<string|int, mixed> $keyFields
+     */
+    private static function printKeyFields($keyFields): string
+    {
+        $parts = [];
+        foreach (((array) $keyFields) as $index => $keyField) {
+            if (\is_string($keyField)) {
+                $parts[] = $keyField;
+            } elseif (\is_array($keyField)) {
+                $parts[] = sprintf('%s { %s }', $index, self::printKeyFields($keyField));
+            } else {
+                throw new \InvalidArgumentException('Invalid keyField config');
+            }
+        }
+
+        return implode(' ', $parts);
+    }
+
     /**
      * @param bool[] $options
      */

From 0769802506b6dbf17b7dac353a4da687f8fb5d26 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 15:05:25 +0300
Subject: [PATCH 08/40] Declare reserved names

---
 src/Enum/TypeEnum.php                | 25 ---------------------
 src/FederatedSchema.php              | 33 ++++++++++++++++++----------
 src/Types/EntityObjectType.php       |  3 ++-
 src/Utils/FederatedSchemaPrinter.php | 20 ++++++++---------
 test/StarWarsSchema.php              | 12 +++++-----
 5 files changed, 40 insertions(+), 53 deletions(-)
 delete mode 100644 src/Enum/TypeEnum.php

diff --git a/src/Enum/TypeEnum.php b/src/Enum/TypeEnum.php
deleted file mode 100644
index 0cbacbd..0000000
--- a/src/Enum/TypeEnum.php
+++ /dev/null
@@ -1,25 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Apollo\Federation\Enum;
-
-final class TypeEnum
-{
-    public const ANY = '_Any';
-    public const ENTITY = '_Entity';
-    public const SERVICE = '_Service';
-
-    /**
-     * @return string[]
-     */
-    public static function getAll(): array
-    {
-        return [self::ANY, self::ENTITY, self::SERVICE];
-    }
-
-    private function __construct()
-    {
-        // forbid creation of an object
-    }
-}
diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index e1d16fc..ebdc19a 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -4,7 +4,6 @@
 
 namespace Apollo\Federation;
 
-use Apollo\Federation\Enum\TypeEnum;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Utils\FederatedSchemaPrinter;
 use GraphQL\Type\Definition\CustomScalarType;
@@ -57,6 +56,18 @@
  */
 class FederatedSchema extends Schema
 {
+    public const RESERVED_TYPE_ANY = '_Any';
+    public const RESERVED_TYPE_ENTITY = '_Entity';
+    public const RESERVED_TYPE_SERVICE = '_Service';
+    public const RESERVED_TYPE_MUTATION = 'Mutation';
+    public const RESERVED_TYPE_QUERY = 'Query';
+
+    public const RESERVED_FIELD_ENTITIES = '_entities';
+    public const RESERVED_FIELD_REPRESENTATIONS = 'representations';
+    public const RESERVED_FIELD_SDL = 'sdl';
+    public const RESERVED_FIELD_SERVICE = '_service';
+    public const RESERVED_FIELD_TYPE_NAME = '__typename';
+
     /** @var EntityObjectType[] */
     protected $entityTypes;
 
@@ -136,9 +147,9 @@ private function getQueryTypeConfig(array $config): array
     private function getQueryTypeServiceFieldConfig(): array
     {
         $serviceType = new ObjectType([
-            'name' => TypeEnum::SERVICE,
+            'name' => self::RESERVED_TYPE_SERVICE,
             'fields' => [
-                'sdl' => [
+                self::RESERVED_FIELD_SDL => [
                     'type' => Type::string(),
                     'resolve' => function () {
                         return FederatedSchemaPrinter::doPrint($this);
@@ -148,7 +159,7 @@ private function getQueryTypeServiceFieldConfig(): array
         ]);
 
         return [
-            '_service' => [
+            self::RESERVED_FIELD_SERVICE => [
                 'type' => Type::nonNull($serviceType),
                 'resolve' => function () {
                     return [];
@@ -169,22 +180,22 @@ private function getQueryTypeEntitiesFieldConfig(?array $config): array
         }
 
         $entityType = new UnionType([
-            'name' => TypeEnum::ENTITY,
+            'name' => self::RESERVED_TYPE_ENTITY,
             'types' => array_values($this->getEntityTypes()),
         ]);
 
         $anyType = new CustomScalarType([
-            'name' => TypeEnum::ANY,
+            'name' => self::RESERVED_TYPE_ANY,
             'serialize' => function ($value) {
                 return $value;
             },
         ]);
 
         return [
-            '_entities' => [
+            self::RESERVED_FIELD_ENTITIES => [
                 'type' => Type::listOf($entityType),
                 'args' => [
-                    'representations' => [
+                    self::RESERVED_FIELD_REPRESENTATIONS => [
                         'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType))),
                     ],
                 ],
@@ -202,9 +213,9 @@ private function getQueryTypeEntitiesFieldConfig(?array $config): array
     private function resolve($root, $args, $context, $info): array
     {
         return array_map(static function ($ref) use ($context, $info) {
-            Utils::invariant(isset($ref['__typename']), 'Type name must be provided in the reference.');
+            Utils::invariant(isset($ref[self::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
 
-            $typeName = $ref['__typename'];
+            $typeName = $ref[self::RESERVED_FIELD_TYPE_NAME];
             $type = $info->schema->getType($typeName);
 
             Utils::invariant(
@@ -220,7 +231,7 @@ private function resolve($root, $args, $context, $info): array
             }
 
             return $type->resolveReference($ref, $context, $info);
-        }, $args['representations']);
+        }, $args[self::RESERVED_FIELD_REPRESENTATIONS]);
     }
 
     /**
diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index fd617c4..a7aa5d7 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -4,6 +4,7 @@
 
 namespace Apollo\Federation\Types;
 
+use Apollo\Federation\FederatedSchema;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Utils\Utils;
 
@@ -120,7 +121,7 @@ private function validateReferenceResolver()
      */
     private function validateReferenceKeys($ref)
     {
-        Utils::invariant(isset($ref['__typename']), 'Type name must be provided in the reference.');
+        Utils::invariant(isset($ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
     }
 
     /**
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 369b3fd..732141c 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -33,7 +33,7 @@
 namespace Apollo\Federation\Utils;
 
 use Apollo\Federation\Enum\DirectiveEnum;
-use Apollo\Federation\Enum\TypeEnum;
+use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
 
@@ -317,7 +317,7 @@ private static function printInputValue($arg): string
     public static function printType(Type $type, array $options = []): string
     {
         if ($type instanceof ScalarType) {
-            if ($type->name !== TypeEnum::ANY) {
+            if ($type->name !== FederatedSchema::RESERVED_TYPE_ANY) {
                 return self::printScalar($type, $options);
             }
 
@@ -329,7 +329,7 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof ObjectType) {
-            if (TypeEnum::SERVICE !== $type->name) {
+            if (FederatedSchema::RESERVED_TYPE_SERVICE !== $type->name) {
                 return self::printObject($type, $options);
             }
 
@@ -341,7 +341,7 @@ public static function printType(Type $type, array $options = []): string
         }
 
         if ($type instanceof UnionType) {
-            if (TypeEnum::ENTITY !== $type->name) {
+            if (FederatedSchema::RESERVED_TYPE_ENTITY !== $type->name) {
                 return self::printUnion($type, $options);
             }
 
@@ -387,8 +387,9 @@ private static function printObject(ObjectType $type, array $options): string
                 )
             : '';
 
-        // FIXME: hardcoded names! They can be different in real.
-        $queryExtends = $type->name === 'Query' || $type->name === 'Mutation' ? 'extend ' : '';
+        $queryExtends = \in_array($type->name, [FederatedSchema::RESERVED_TYPE_QUERY, FederatedSchema::RESERVED_TYPE_MUTATION], true)
+            ? 'extend '
+            : '';
 
         return self::printDescription($options, $type) .
             sprintf(
@@ -444,11 +445,10 @@ private static function printFields(array $options, TypeWithFields $type): strin
     {
         $fields = array_values($type->getFields());
 
-        // FIXME it looks like hardcoded name. Potentially, it can be different!
-        if ($type->name === 'Query') {
+        if ($type->name === FederatedSchema::RESERVED_TYPE_QUERY) {
             $fields = array_filter($fields, static function (FieldDefinition $field): bool {
-                //TODO use constants instead of magic scalar values
-                return $field->name !== '_service' && $field->name !== '_entities';
+                return $field->name !== FederatedSchema::RESERVED_FIELD_SERVICE
+                    && $field->name !== FederatedSchema::RESERVED_FIELD_ENTITIES;
             });
         }
 
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index 5594896..9ec1f8b 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -37,7 +37,7 @@ public static function getEpisodesSchemaCustomResolver(): FederatedSchema
                         $type = $info->schema->getType($typeName);
                         $ref["id"] = $ref["id"] + 1;
                         return $type->resolveReference($ref);
-                    }, $args['representations']);
+                    }, $args[FederatedSchema::RESERVED_FIELD_REPRESENTATIONS]);
                 }
             ]);
         }
@@ -49,7 +49,7 @@ private static function getQueryType(): ObjectType
         $episodeType = self::getEpisodeType();
 
         $queryType = new ObjectType([
-            'name' => 'Query',
+            'name' => FederatedSchema::RESERVED_TYPE_QUERY,
             'fields' => [
                 'episodes' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull($episodeType))),
@@ -86,8 +86,8 @@ private static function getEpisodeType(): EntityObjectType
                     'provides' => 'name'
                 ]
             ],
-            'keyFields' => ['id'],
-            '__resolveReference' => function ($ref) {
+            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
+            EntityObjectType::FIELD_REFERENCE_RESOLVER => function ($ref) {
                 // print_r($ref);
                 $entity = StarWarsData::getEpisodeById($ref['id']);
                 $entity["__typename"] = "Episode";
@@ -118,7 +118,7 @@ private static function getCharacterType(): EntityRefObjectType
                     'requires' => 'name'
                 ]
             ],
-            'keyFields' => ['id']
+            EntityObjectType::FIELD_KEY_FIELDS => ['id']
         ]);
     }
 
@@ -137,7 +137,7 @@ private static function getLocationType(): EntityRefObjectType
                     'isExternal' => true
                 ]
             ],
-            'keyFields' => ['id']
+            EntityObjectType::FIELD_KEY_FIELDS => ['id']
         ]);
     }
 }

From 684970629f3f9111a90a12adc5828997796a33b2 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 17:51:28 +0300
Subject: [PATCH 09/40] Fix code style

---
 src/Utils/FederatedSchemaPrinter.php | 37 ++++++++++++----------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 732141c..24820be 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -1,7 +1,6 @@
 <?php
 
 /**
- * 
  * This source file includes modified code from webonyx/graphql-php.
  *
  * Copyright (c) 2015-present, Webonyx, LLC.
@@ -36,7 +35,6 @@
 use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
-
 use GraphQL\Error\Error;
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
@@ -62,7 +60,6 @@
 use function array_map;
 use function array_merge;
 use function array_values;
-use function count;
 use function explode;
 use function implode;
 use function ksort;
@@ -70,7 +67,6 @@
 use function preg_match_all;
 use function sprintf;
 use function str_replace;
-use function strlen;
 use function substr;
 
 /**
@@ -80,11 +76,10 @@ class FederatedSchemaPrinter
 {
     /**
      * Accepts options as a second argument:
-     *
      *    - commentDescriptions:
      *        Provide true to use preceding comments as the description.
      *
-     * @param bool[] $options
+     * @param array{ commentDescriptions: bool } $options
      *
      * @api
      */
@@ -157,11 +152,11 @@ private static function printDirective(Directive $directive, array $options): st
      */
     private static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
     {
-        if (!$def->description) {
+        if (!isset($def->description) || !$def->description) {
             return '';
         }
 
-        $lines = self::descriptionLines($def->description, 120 - strlen($indentation));
+        $lines = self::descriptionLines($def->description, 120 - \strlen($indentation));
 
         if (isset($options['commentDescriptions'])) {
             return self::printDescriptionWithComments($lines, $indentation, $firstInBlock);
@@ -170,7 +165,7 @@ private static function printDescription(array $options, $def, string $indentati
         $description = $indentation && !$firstInBlock ? "\n" . $indentation . '"""' : $indentation . '"""';
 
         // In some circumstances, a single line can be used for the description.
-        if (count($lines) === 1 && mb_strlen($lines[0]) < 70 && substr($lines[0], -1) !== '"') {
+        if (1 === \count($lines) && mb_strlen($lines[0]) < 70 && '"' !== substr($lines[0], -1)) {
             return $description . self::escapeQuote($lines[0]) . "\"\"\"\n";
         }
 
@@ -183,8 +178,8 @@ private static function printDescription(array $options, $def, string $indentati
 
         $lineLength = \count($lines);
 
-        for ($i = 0; $i < $lineLength; $i++) {
-            if ($i !== 0 || !$hasLeadingSpace) {
+        for ($i = 0; $i < $lineLength; ++$i) {
+            if (0 !== $i || !$hasLeadingSpace) {
                 $description .= $indentation;
             }
             $description .= self::escapeQuote($lines[$i]) . "\n";
@@ -204,7 +199,7 @@ private static function descriptionLines(string $description, int $maxLen): arra
         $rawLines = explode("\n", $description);
 
         foreach ($rawLines as $line) {
-            if ($line === '') {
+            if ('' === $line) {
                 $lines[] = $line;
             } else {
                 // For > 120 character long lines, cut at space boundaries into sublines
@@ -225,7 +220,7 @@ private static function descriptionLines(string $description, int $maxLen): arra
      */
     private static function breakLine(string $line, int $maxLen): array
     {
-        if (strlen($line) < $maxLen + 5) {
+        if (\strlen($line) < $maxLen + 5) {
             return [$line];
         }
 
@@ -244,7 +239,7 @@ private static function printDescriptionWithComments(array $lines, string $inden
         $description = $indentation && !$firstInBlock ? "\n" : '';
 
         foreach ($lines as $line) {
-            if ($line === '') {
+            if ('' === $line) {
                 $description .= $indentation . "#\n";
             } else {
                 $description .= $indentation . '# ' . $line . "\n";
@@ -317,7 +312,7 @@ private static function printInputValue($arg): string
     public static function printType(Type $type, array $options = []): string
     {
         if ($type instanceof ScalarType) {
-            if ($type->name !== FederatedSchema::RESERVED_TYPE_ANY) {
+            if (FederatedSchema::RESERVED_TYPE_ANY !== $type->name) {
                 return self::printScalar($type, $options);
             }
 
@@ -445,10 +440,10 @@ private static function printFields(array $options, TypeWithFields $type): strin
     {
         $fields = array_values($type->getFields());
 
-        if ($type->name === FederatedSchema::RESERVED_TYPE_QUERY) {
+        if (FederatedSchema::RESERVED_TYPE_QUERY === $type->name) {
             $fields = array_filter($fields, static function (FieldDefinition $field): bool {
-                return $field->name !== FederatedSchema::RESERVED_FIELD_SERVICE
-                    && $field->name !== FederatedSchema::RESERVED_FIELD_ENTITIES;
+                return FederatedSchema::RESERVED_FIELD_SERVICE !== $field->name
+                    && FederatedSchema::RESERVED_FIELD_ENTITIES !== $field->name;
             });
         }
 
@@ -481,7 +476,7 @@ private static function printDeprecated($fieldOrEnumVal): string
         if (empty($reason)) {
             return '';
         }
-        if ($reason === '' || $reason === Directive::DEFAULT_DEPRECATION_REASON) {
+        if ('' === $reason || Directive::DEFAULT_DEPRECATION_REASON === $reason) {
             return ' @deprecated';
         }
 
@@ -493,7 +488,7 @@ private static function printFieldFederatedDirectives(FieldDefinition $field): s
         $directives = [];
 
         if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL])
-            && $field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL] === true
+            && true === $field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL]
         ) {
             $directives[] = '@external';
         }
@@ -604,7 +599,7 @@ static function ($f, $i) use ($options) {
     }
 
     /**
-     * @param bool[] $options
+     * @param array{ commentDescriptions: bool } $options
      *
      * @api
      */

From df465205ca933b204e5541ca38fcd3e47c41240d Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 18:32:25 +0300
Subject: [PATCH 10/40] Fixes during investigation

---
 .gitignore                        |  1 +
 README.md                         |  3 ++-
 src/FederatedSchema.php           |  2 +-
 src/Types/EntityObjectType.php    |  2 +-
 src/Types/EntityRefObjectType.php | 12 +-----------
 test/DirectivesTest.php           | 14 ++++++--------
 test/EntitiesTest.php             |  9 +++------
 test/SchemaTest.php               |  9 ++-------
 8 files changed, 17 insertions(+), 35 deletions(-)

diff --git a/.gitignore b/.gitignore
index 7303759..f5aea2f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+.idea
 composer.phar
 /vendor/
 /node_modules/
diff --git a/README.md b/README.md
index cb391f7..589c85c 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ An entity is an object type that you define canonically in one subgraph and can
 
 ```php
 use Apollo\Federation\Types\EntityObjectType;
+use GraphQL\Type\Definition\Type;
 
 $userType = new EntityObjectType([
     'name' => 'User',
@@ -34,7 +35,7 @@ $userType = new EntityObjectType([
 ]);
 ```
 
-* `keyFields` — defines the entity's primary key, which consists of one or more of the type's. An entity's key cannot include fields that return a union or interface.
+* `keyFields` — defines the entity's primary key, which consists of one or more of the fields. An entity's key cannot include fields that return a union or interface.
 
 * `__resolveReference` — resolves the representation of the entity from the provided reference. Subgraphs use representations to reference entities from other subgraphs. A representation requires only an explicit __typename definition and values for the entity's primary key fields.
 
diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index ebdc19a..757109e 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -17,7 +17,7 @@
 use GraphQL\Utils\Utils;
 
 /**
- * A federated GraphQL schema definition {@see https://www.apollographql.com/docs/apollo-server/federation/introduction }.
+ * A federated GraphQL schema definition see related docs {@see https://www.apollographql.com/docs/apollo-server/federation/introduction }.
  *
  * A federated schema defines a self-contained GraphQL service that can be merged with
  * other services by the [Apollo Gateway](https://www.apollographql.com/docs/intro/platform/#gateway)
diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index a7aa5d7..227e6bb 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -13,7 +13,7 @@
  * connection points between services and form the basic building blocks of a federated
  * graph. Entities have a primary key whose value uniquely identifies a specific instance
  * of the type, similar to the function of a primary key in a SQL table
- * {@see https://www.apollographql.com/docs/apollo-server/federation/core-concepts/#entities-and-keys }.
+ * see related docs {@see https://www.apollographql.com/docs/apollo-server/federation/core-concepts/#entities-and-keys }.
  *
  * The `keyFields` property is required in the configuration, indicating the fields that
  * serve as the unique keys or identifiers of the entity.
diff --git a/src/Types/EntityRefObjectType.php b/src/Types/EntityRefObjectType.php
index a798ec4..3789755 100644
--- a/src/Types/EntityRefObjectType.php
+++ b/src/Types/EntityRefObjectType.php
@@ -7,19 +7,9 @@
 /**
  * An entity reference is a type referencing an entity owned by another service. Usually,
  * entity references are stub types containing only the key fields necessary for the
- * [Apollo Gateway](https://www.apollographql.com/docs/intro/platform/#gateway) to
+ * Apollo Gateway {@see https://www.apollographql.com/docs/intro/platform/#gateway } to
  * resolve the entity during query execution.
  */
 class EntityRefObjectType extends EntityObjectType
 {
-    /** @var array */
-    private $keyFields;
-
-    /**
-     * @param mixed[] $config
-     */
-    public function __construct(array $config)
-    {
-        parent::__construct($config);
-    }
 }
diff --git a/test/DirectivesTest.php b/test/DirectivesTest.php
index 67c4871..474e477 100644
--- a/test/DirectivesTest.php
+++ b/test/DirectivesTest.php
@@ -4,16 +4,14 @@
 
 namespace Apollo\Federation\Tests;
 
-use PHPUnit\Framework\TestCase;
-use Spatie\Snapshots\MatchesSnapshots;
-
-use GraphQL\Type\Schema;
-use GraphQL\Type\Definition\Type;
-use GraphQL\Type\Definition\ObjectType;
+use Apollo\Federation\Directives;
 use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Schema;
 use GraphQL\Utils\SchemaPrinter;
-
-use Apollo\Federation\Directives;
+use PHPUnit\Framework\TestCase;
+use Spatie\Snapshots\MatchesSnapshots;
 
 class DirectivesTest extends TestCase
 {
diff --git a/test/EntitiesTest.php b/test/EntitiesTest.php
index de61813..2acb5d5 100644
--- a/test/EntitiesTest.php
+++ b/test/EntitiesTest.php
@@ -4,14 +4,11 @@
 
 namespace Apollo\Federation\Tests;
 
-use PHPUnit\Framework\TestCase;
-use Spatie\Snapshots\MatchesSnapshots;
-
-use GraphQL\Type\Definition\Type;
-use GraphQL\Error\InvariantViolation;
-
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
+use GraphQL\Type\Definition\Type;
+use PHPUnit\Framework\TestCase;
+use Spatie\Snapshots\MatchesSnapshots;
 
 class EntitiesTest extends TestCase
 {
diff --git a/test/SchemaTest.php b/test/SchemaTest.php
index 8f9b882..4262bba 100644
--- a/test/SchemaTest.php
+++ b/test/SchemaTest.php
@@ -4,15 +4,10 @@
 
 namespace Apollo\Federation\Tests;
 
-use PHPUnit\Framework\TestCase;
-use Spatie\Snapshots\MatchesSnapshots;
-
 use GraphQL\GraphQL;
-use GraphQL\Type\Definition\Type;
 use GraphQL\Utils\SchemaPrinter;
-
-use Apollo\Federation\Tests\StarWarsSchema;
-use Apollo\Federation\Tests\DungeonsAndDragonsSchema;
+use PHPUnit\Framework\TestCase;
+use Spatie\Snapshots\MatchesSnapshots;
 
 class SchemaTest extends TestCase
 {

From 79e14dce2bf41cd7566d593ae0c03b552eaab4a9 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 18:45:36 +0300
Subject: [PATCH 11/40] Update phpDocs

---
 src/Utils/FederatedSchemaPrinter.php | 30 ++++++++++++++--------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 24820be..8014deb 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -79,7 +79,7 @@ class FederatedSchemaPrinter
      *    - commentDescriptions:
      *        Provide true to use preceding comments as the description.
      *
-     * @param array{ commentDescriptions: bool } $options
+     * @param array<string, bool> $options
      *
      * @api
      */
@@ -103,7 +103,7 @@ public static function isFederatedDirective(Directive $type): bool
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printFilteredSchema(Schema $schema, callable $directiveFilter, callable $typeFilter, array $options): string
     {
@@ -134,7 +134,7 @@ private static function printFilteredSchema(Schema $schema, callable $directiveF
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printDirective(Directive $directive, array $options): string
     {
@@ -147,7 +147,7 @@ private static function printDirective(Directive $directive, array $options): st
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      * @param Directive|EnumValueDefinition|FieldArgument|Type|object $def
      */
     private static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
@@ -307,7 +307,7 @@ private static function printInputValue($arg): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     public static function printType(Type $type, array $options = []): string
     {
@@ -355,7 +355,7 @@ public static function printType(Type $type, array $options = []): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printScalar(ScalarType $type, array $options): string
     {
@@ -363,7 +363,7 @@ private static function printScalar(ScalarType $type, array $options): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printObject(ObjectType $type, array $options): string
     {
@@ -397,7 +397,7 @@ private static function printObject(ObjectType $type, array $options): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printEntityObject(EntityObjectType $type, array $options): string
     {
@@ -433,7 +433,7 @@ private static function printEntityObject(EntityObjectType $type, array $options
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      * @param EntityObjectType|InterfaceType|ObjectType $type
      */
     private static function printFields(array $options, TypeWithFields $type): string
@@ -505,7 +505,7 @@ private static function printFieldFederatedDirectives(FieldDefinition $field): s
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printInterface(InterfaceType $type, array $options): string
     {
@@ -536,7 +536,7 @@ private static function printKeyFields($keyFields): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printUnion(UnionType $type, array $options): string
     {
@@ -545,7 +545,7 @@ private static function printUnion(UnionType $type, array $options): string
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printEnum(EnumType $type, array $options): string
     {
@@ -555,7 +555,7 @@ private static function printEnum(EnumType $type, array $options): string
 
     /**
      * @param EnumValueDefinition[] $values
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printEnumValues(array $values, array $options): string
     {
@@ -575,7 +575,7 @@ static function ($value, $i) use ($options) {
     }
 
     /**
-     * @param bool[] $options
+     * @param array<string, bool> $options
      */
     private static function printInputObject(InputObjectType $type, array $options): string
     {
@@ -599,7 +599,7 @@ static function ($f, $i) use ($options) {
     }
 
     /**
-     * @param array{ commentDescriptions: bool } $options
+     * @param array<string, bool> $options
      *
      * @api
      */

From 245f9adc7d36cf0a73a714aa4481660d393f82c3 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 1 Aug 2022 18:58:34 +0300
Subject: [PATCH 12/40] Make printer better extendable

---
 src/Utils/FederatedSchemaPrinter.php | 130 +++++++++++++--------------
 1 file changed, 65 insertions(+), 65 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 8014deb..419014e 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -85,10 +85,10 @@ class FederatedSchemaPrinter
      */
     public static function doPrint(Schema $schema, array $options = []): string
     {
-        return self::printFilteredSchema(
+        return static::printFilteredSchema(
             $schema,
             static function (Directive $type): bool {
-                return !Directive::isSpecifiedDirective($type) && !self::isFederatedDirective($type);
+                return !Directive::isSpecifiedDirective($type) && !static::isFederatedDirective($type);
             },
             static function (Type $type): bool {
                 return !Type::isBuiltInType($type);
@@ -105,7 +105,7 @@ public static function isFederatedDirective(Directive $type): bool
     /**
      * @param array<string, bool> $options
      */
-    private static function printFilteredSchema(Schema $schema, callable $directiveFilter, callable $typeFilter, array $options): string
+    protected static function printFilteredSchema(Schema $schema, callable $directiveFilter, callable $typeFilter, array $options): string
     {
         $directives = array_filter($schema->getDirectives(), static function (Directive $directive) use ($directiveFilter): bool {
             return $directiveFilter($directive);
@@ -122,10 +122,10 @@ private static function printFilteredSchema(Schema $schema, callable $directiveF
                 array_filter(
                     array_merge(
                         array_map(static function (Directive $directive) use ($options) {
-                            return self::printDirective($directive, $options);
+                            return static::printDirective($directive, $options);
                         }, $directives),
                         array_map(static function (Type $type) use ($options) {
-                            return self::printType($type, $options);
+                            return static::printType($type, $options);
                         }, $types)
                     )
                 )
@@ -136,12 +136,12 @@ private static function printFilteredSchema(Schema $schema, callable $directiveF
     /**
      * @param array<string, bool> $options
      */
-    private static function printDirective(Directive $directive, array $options): string
+    protected static function printDirective(Directive $directive, array $options): string
     {
-        return self::printDescription($options, $directive) .
+        return static::printDescription($options, $directive) .
             'directive @' .
             $directive->name .
-            self::printArgs($options, $directive->args) .
+            static::printArgs($options, $directive->args) .
             ' on ' .
             implode(' | ', $directive->locations);
     }
@@ -150,23 +150,23 @@ private static function printDirective(Directive $directive, array $options): st
      * @param array<string, bool> $options
      * @param Directive|EnumValueDefinition|FieldArgument|Type|object $def
      */
-    private static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
+    protected static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
     {
         if (!isset($def->description) || !$def->description) {
             return '';
         }
 
-        $lines = self::descriptionLines($def->description, 120 - \strlen($indentation));
+        $lines = static::descriptionLines($def->description, 120 - \strlen($indentation));
 
         if (isset($options['commentDescriptions'])) {
-            return self::printDescriptionWithComments($lines, $indentation, $firstInBlock);
+            return static::printDescriptionWithComments($lines, $indentation, $firstInBlock);
         }
 
         $description = $indentation && !$firstInBlock ? "\n" . $indentation . '"""' : $indentation . '"""';
 
         // In some circumstances, a single line can be used for the description.
         if (1 === \count($lines) && mb_strlen($lines[0]) < 70 && '"' !== substr($lines[0], -1)) {
-            return $description . self::escapeQuote($lines[0]) . "\"\"\"\n";
+            return $description . static::escapeQuote($lines[0]) . "\"\"\"\n";
         }
 
         // Format a multi-line block quote to account for leading space.
@@ -182,7 +182,7 @@ private static function printDescription(array $options, $def, string $indentati
             if (0 !== $i || !$hasLeadingSpace) {
                 $description .= $indentation;
             }
-            $description .= self::escapeQuote($lines[$i]) . "\n";
+            $description .= static::escapeQuote($lines[$i]) . "\n";
         }
 
         $description .= $indentation . "\"\"\"\n";
@@ -193,7 +193,7 @@ private static function printDescription(array $options, $def, string $indentati
     /**
      * @return string[]
      */
-    private static function descriptionLines(string $description, int $maxLen): array
+    protected static function descriptionLines(string $description, int $maxLen): array
     {
         $lines = [];
         $rawLines = explode("\n", $description);
@@ -204,7 +204,7 @@ private static function descriptionLines(string $description, int $maxLen): arra
             } else {
                 // For > 120 character long lines, cut at space boundaries into sublines
                 // of ~80 chars.
-                $sublines = self::breakLine($line, $maxLen);
+                $sublines = static::breakLine($line, $maxLen);
 
                 foreach ($sublines as $subline) {
                     $lines[] = $subline;
@@ -218,7 +218,7 @@ private static function descriptionLines(string $description, int $maxLen): arra
     /**
      * @return string[]
      */
-    private static function breakLine(string $line, int $maxLen): array
+    protected static function breakLine(string $line, int $maxLen): array
     {
         if (\strlen($line) < $maxLen + 5) {
             return [$line];
@@ -234,7 +234,7 @@ private static function breakLine(string $line, int $maxLen): array
     /**
      * @param string[] $lines
      */
-    private static function printDescriptionWithComments(array $lines, string $indentation, bool $firstInBlock): string
+    protected static function printDescriptionWithComments(array $lines, string $indentation, bool $firstInBlock): string
     {
         $description = $indentation && !$firstInBlock ? "\n" : '';
 
@@ -249,7 +249,7 @@ private static function printDescriptionWithComments(array $lines, string $inden
         return $description;
     }
 
-    private static function escapeQuote(string $line): string
+    protected static function escapeQuote(string $line): string
     {
         return str_replace('"""', '\\"""', $line);
     }
@@ -258,7 +258,7 @@ private static function escapeQuote(string $line): string
      * @param bool[]               $options
      * @param FieldArgument[]|null $args
      */
-    private static function printArgs(array $options, $args, string $indentation = ''): string
+    protected static function printArgs(array $options, $args, string $indentation = ''): string
     {
         if (!$args) {
             return '';
@@ -270,7 +270,7 @@ private static function printArgs(array $options, $args, string $indentation = '
                 return empty($arg->description);
             })
         ) {
-            return '(' . implode(', ', array_map('self::printInputValue', $args)) . ')';
+            return '(' . implode(', ', array_map('static::printInputValue', $args)) . ')';
         }
 
         return sprintf(
@@ -279,10 +279,10 @@ private static function printArgs(array $options, $args, string $indentation = '
                 "\n",
                 array_map(
                     static function (FieldArgument $arg, $i) use ($indentation, $options): string {
-                        return self::printDescription($options, $arg, '  ' . $indentation, !$i) .
+                        return static::printDescription($options, $arg, '  ' . $indentation, !$i) .
                             '  ' .
                             $indentation .
-                            self::printInputValue($arg);
+                            static::printInputValue($arg);
                     },
                     $args,
                     array_keys($args)
@@ -295,7 +295,7 @@ static function (FieldArgument $arg, $i) use ($indentation, $options): string {
     /**
      * @param InputObjectField|FieldArgument $arg
      */
-    private static function printInputValue($arg): string
+    protected static function printInputValue($arg): string
     {
         $argDecl = $arg->name . ': ' . (string) $arg->getType();
 
@@ -313,42 +313,42 @@ public static function printType(Type $type, array $options = []): string
     {
         if ($type instanceof ScalarType) {
             if (FederatedSchema::RESERVED_TYPE_ANY !== $type->name) {
-                return self::printScalar($type, $options);
+                return static::printScalar($type, $options);
             }
 
             return '';
         }
 
         if ($type instanceof EntityObjectType || $type instanceof EntityRefObjectType) {
-            return self::printEntityObject($type, $options);
+            return static::printEntityObject($type, $options);
         }
 
         if ($type instanceof ObjectType) {
             if (FederatedSchema::RESERVED_TYPE_SERVICE !== $type->name) {
-                return self::printObject($type, $options);
+                return static::printObject($type, $options);
             }
 
             return '';
         }
 
         if ($type instanceof InterfaceType) {
-            return self::printInterface($type, $options);
+            return static::printInterface($type, $options);
         }
 
         if ($type instanceof UnionType) {
             if (FederatedSchema::RESERVED_TYPE_ENTITY !== $type->name) {
-                return self::printUnion($type, $options);
+                return static::printUnion($type, $options);
             }
 
             return '';
         }
 
         if ($type instanceof EnumType) {
-            return self::printEnum($type, $options);
+            return static::printEnum($type, $options);
         }
 
         if ($type instanceof InputObjectType) {
-            return self::printInputObject($type, $options);
+            return static::printInputObject($type, $options);
         }
 
         throw new Error(sprintf('Unknown type: %s.', Utils::printSafe($type)));
@@ -357,15 +357,15 @@ public static function printType(Type $type, array $options = []): string
     /**
      * @param array<string, bool> $options
      */
-    private static function printScalar(ScalarType $type, array $options): string
+    protected static function printScalar(ScalarType $type, array $options): string
     {
-        return sprintf('%sscalar %s', self::printDescription($options, $type), $type->name);
+        return sprintf('%sscalar %s', static::printDescription($options, $type), $type->name);
     }
 
     /**
      * @param array<string, bool> $options
      */
-    private static function printObject(ObjectType $type, array $options): string
+    protected static function printObject(ObjectType $type, array $options): string
     {
         if (empty($type->getFields())) {
             return '';
@@ -386,20 +386,20 @@ private static function printObject(ObjectType $type, array $options): string
             ? 'extend '
             : '';
 
-        return self::printDescription($options, $type) .
+        return static::printDescription($options, $type) .
             sprintf(
                 "%stype %s%s {\n%s\n}",
                 $queryExtends,
                 $type->name,
                 $implementedInterfaces,
-                self::printFields($options, $type)
+                static::printFields($options, $type)
             );
     }
 
     /**
      * @param array<string, bool> $options
      */
-    private static function printEntityObject(EntityObjectType $type, array $options): string
+    protected static function printEntityObject(EntityObjectType $type, array $options): string
     {
         $interfaces = $type->getInterfaces();
         $implementedInterfaces = !empty($interfaces)
@@ -415,20 +415,20 @@ private static function printEntityObject(EntityObjectType $type, array $options
         $keyDirective = '';
 
         foreach ($type->getKeyFields() as $keyField) {
-            $keyDirective = $keyDirective . sprintf(' @key(fields: "%s")', self::printKeyFields($keyField));
+            $keyDirective = $keyDirective . sprintf(' @key(fields: "%s")', static::printKeyFields($keyField));
         }
 
         $isEntityRef = $type instanceof EntityRefObjectType;
         $extends = $isEntityRef ? 'extend ' : '';
 
-        return self::printDescription($options, $type) .
+        return static::printDescription($options, $type) .
             sprintf(
                 "%stype %s%s%s {\n%s\n}",
                 $extends,
                 $type->name,
                 $implementedInterfaces,
                 $keyDirective,
-                self::printFields($options, $type)
+                static::printFields($options, $type)
             );
     }
 
@@ -436,7 +436,7 @@ private static function printEntityObject(EntityObjectType $type, array $options
      * @param array<string, bool> $options
      * @param EntityObjectType|InterfaceType|ObjectType $type
      */
-    private static function printFields(array $options, TypeWithFields $type): string
+    protected static function printFields(array $options, TypeWithFields $type): string
     {
         $fields = array_values($type->getFields());
 
@@ -451,15 +451,15 @@ private static function printFields(array $options, TypeWithFields $type): strin
             "\n",
             array_map(
                 static function (FieldDefinition $f, $i) use ($options) {
-                    return self::printDescription($options, $f, '  ', !$i) .
+                    return static::printDescription($options, $f, '  ', !$i) .
                         '  ' .
                         $f->name .
-                        self::printArgs($options, $f->args, '  ') .
+                        static::printArgs($options, $f->args, '  ') .
                         ': ' .
                         (string) $f->getType() .
-                        self::printDeprecated($f) .
+                        static::printDeprecated($f) .
                         ' ' .
-                        self::printFieldFederatedDirectives($f);
+                        static::printFieldFederatedDirectives($f);
                 },
                 $fields,
                 array_keys($fields)
@@ -470,7 +470,7 @@ static function (FieldDefinition $f, $i) use ($options) {
     /**
      * @param EnumValueDefinition|FieldDefinition $fieldOrEnumVal
      */
-    private static function printDeprecated($fieldOrEnumVal): string
+    protected static function printDeprecated($fieldOrEnumVal): string
     {
         $reason = $fieldOrEnumVal->deprecationReason;
         if (empty($reason)) {
@@ -483,7 +483,7 @@ private static function printDeprecated($fieldOrEnumVal): string
         return ' @deprecated(reason: ' . Printer::doPrint(AST::astFromValue($reason, Type::string())) . ')';
     }
 
-    private static function printFieldFederatedDirectives(FieldDefinition $field): string
+    protected static function printFieldFederatedDirectives(FieldDefinition $field): string
     {
         $directives = [];
 
@@ -494,11 +494,11 @@ private static function printFieldFederatedDirectives(FieldDefinition $field): s
         }
 
         if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES])) {
-            $directives[] = sprintf('@provides(fields: "%s")', self::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]));
+            $directives[] = sprintf('@provides(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]));
         }
 
         if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES])) {
-            $directives[] = sprintf('@requires(fields: "%s")', self::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]));
+            $directives[] = sprintf('@requires(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]));
         }
 
         return implode(' ', $directives);
@@ -507,10 +507,10 @@ private static function printFieldFederatedDirectives(FieldDefinition $field): s
     /**
      * @param array<string, bool> $options
      */
-    private static function printInterface(InterfaceType $type, array $options): string
+    protected static function printInterface(InterfaceType $type, array $options): string
     {
-        return self::printDescription($options, $type) .
-            sprintf("interface %s {\n%s\n}", $type->name, self::printFields($options, $type));
+        return static::printDescription($options, $type) .
+            sprintf("interface %s {\n%s\n}", $type->name, static::printFields($options, $type));
     }
 
     /**
@@ -519,14 +519,14 @@ private static function printInterface(InterfaceType $type, array $options): str
      *
      * @param string|array<string|int, mixed> $keyFields
      */
-    private static function printKeyFields($keyFields): string
+    protected static function printKeyFields($keyFields): string
     {
         $parts = [];
         foreach (((array) $keyFields) as $index => $keyField) {
             if (\is_string($keyField)) {
                 $parts[] = $keyField;
             } elseif (\is_array($keyField)) {
-                $parts[] = sprintf('%s { %s }', $index, self::printKeyFields($keyField));
+                $parts[] = sprintf('%s { %s }', $index, static::printKeyFields($keyField));
             } else {
                 throw new \InvalidArgumentException('Invalid keyField config');
             }
@@ -538,35 +538,35 @@ private static function printKeyFields($keyFields): string
     /**
      * @param array<string, bool> $options
      */
-    private static function printUnion(UnionType $type, array $options): string
+    protected static function printUnion(UnionType $type, array $options): string
     {
-        return self::printDescription($options, $type) .
+        return static::printDescription($options, $type) .
             sprintf('union %s = %s', $type->name, implode(' | ', $type->getTypes()));
     }
 
     /**
      * @param array<string, bool> $options
      */
-    private static function printEnum(EnumType $type, array $options): string
+    protected static function printEnum(EnumType $type, array $options): string
     {
-        return self::printDescription($options, $type) .
-            sprintf("enum %s {\n%s\n}", $type->name, self::printEnumValues($type->getValues(), $options));
+        return static::printDescription($options, $type) .
+            sprintf("enum %s {\n%s\n}", $type->name, static::printEnumValues($type->getValues(), $options));
     }
 
     /**
      * @param EnumValueDefinition[] $values
      * @param array<string, bool> $options
      */
-    private static function printEnumValues(array $values, array $options): string
+    protected static function printEnumValues(array $values, array $options): string
     {
         return implode(
             "\n",
             array_map(
                 static function ($value, $i) use ($options) {
-                    return self::printDescription($options, $value, '  ', !$i) .
+                    return static::printDescription($options, $value, '  ', !$i) .
                         '  ' .
                         $value->name .
-                        self::printDeprecated($value);
+                        static::printDeprecated($value);
                 },
                 $values,
                 array_keys($values)
@@ -577,11 +577,11 @@ static function ($value, $i) use ($options) {
     /**
      * @param array<string, bool> $options
      */
-    private static function printInputObject(InputObjectType $type, array $options): string
+    protected static function printInputObject(InputObjectType $type, array $options): string
     {
         $fields = array_values($type->getFields());
 
-        return self::printDescription($options, $type) .
+        return static::printDescription($options, $type) .
             sprintf(
                 "input %s {\n%s\n}",
                 $type->name,
@@ -589,7 +589,7 @@ private static function printInputObject(InputObjectType $type, array $options):
                     "\n",
                     array_map(
                         static function ($f, $i) use ($options) {
-                            return self::printDescription($options, $f, '  ', !$i) . '  ' . self::printInputValue($f);
+                            return static::printDescription($options, $f, '  ', !$i) . '  ' . static::printInputValue($f);
                         },
                         $fields,
                         array_keys($fields)
@@ -605,7 +605,7 @@ static function ($f, $i) use ($options) {
      */
     public static function printIntrospectionSchema(Schema $schema, array $options = []): string
     {
-        return self::printFilteredSchema(
+        return static::printFilteredSchema(
             $schema,
             [Directive::class, 'isSpecifiedDirective'],
             [Introspection::class, 'isIntrospectionType'],

From cd86cde752d526daffff1525431dd58439b4dae9 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 09:41:13 +0300
Subject: [PATCH 13/40] Extend base schema printer and reduce copy-paste

---
 src/Utils/FederatedSchemaPrinter.php | 379 +--------------------------
 1 file changed, 9 insertions(+), 370 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 419014e..096291d 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -35,44 +35,28 @@
 use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
-use GraphQL\Error\Error;
-use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
-use GraphQL\Type\Definition\EnumType;
-use GraphQL\Type\Definition\EnumValueDefinition;
-use GraphQL\Type\Definition\FieldArgument;
 use GraphQL\Type\Definition\FieldDefinition;
-use GraphQL\Type\Definition\InputObjectField;
-use GraphQL\Type\Definition\InputObjectType;
 use GraphQL\Type\Definition\InterfaceType;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\ScalarType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\TypeWithFields;
 use GraphQL\Type\Definition\UnionType;
-use GraphQL\Type\Introspection;
 use GraphQL\Type\Schema;
-use GraphQL\Utils\AST;
-use GraphQL\Utils\Utils;
+use GraphQL\Utils\SchemaPrinter;
 
 use function array_filter;
 use function array_keys;
 use function array_map;
-use function array_merge;
 use function array_values;
-use function explode;
 use function implode;
-use function ksort;
-use function mb_strlen;
-use function preg_match_all;
 use function sprintf;
-use function str_replace;
-use function substr;
 
 /**
  * Given an instance of Schema, prints it in GraphQL type language.
  */
-class FederatedSchemaPrinter
+class FederatedSchemaPrinter extends SchemaPrinter
 {
     /**
      * Accepts options as a second argument:
@@ -102,264 +86,22 @@ public static function isFederatedDirective(Directive $type): bool
         return \in_array($type->name, DirectiveEnum::getAll(), true);
     }
 
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printFilteredSchema(Schema $schema, callable $directiveFilter, callable $typeFilter, array $options): string
-    {
-        $directives = array_filter($schema->getDirectives(), static function (Directive $directive) use ($directiveFilter): bool {
-            return $directiveFilter($directive);
-        });
-
-        $types = $schema->getTypeMap();
-        ksort($types);
-        $types = array_filter($types, $typeFilter);
-
-        return sprintf(
-            "%s\n",
-            implode(
-                "\n\n",
-                array_filter(
-                    array_merge(
-                        array_map(static function (Directive $directive) use ($options) {
-                            return static::printDirective($directive, $options);
-                        }, $directives),
-                        array_map(static function (Type $type) use ($options) {
-                            return static::printType($type, $options);
-                        }, $types)
-                    )
-                )
-            )
-        );
-    }
-
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printDirective(Directive $directive, array $options): string
-    {
-        return static::printDescription($options, $directive) .
-            'directive @' .
-            $directive->name .
-            static::printArgs($options, $directive->args) .
-            ' on ' .
-            implode(' | ', $directive->locations);
-    }
-
-    /**
-     * @param array<string, bool> $options
-     * @param Directive|EnumValueDefinition|FieldArgument|Type|object $def
-     */
-    protected static function printDescription(array $options, $def, string $indentation = '', bool $firstInBlock = true): string
-    {
-        if (!isset($def->description) || !$def->description) {
-            return '';
-        }
-
-        $lines = static::descriptionLines($def->description, 120 - \strlen($indentation));
-
-        if (isset($options['commentDescriptions'])) {
-            return static::printDescriptionWithComments($lines, $indentation, $firstInBlock);
-        }
-
-        $description = $indentation && !$firstInBlock ? "\n" . $indentation . '"""' : $indentation . '"""';
-
-        // In some circumstances, a single line can be used for the description.
-        if (1 === \count($lines) && mb_strlen($lines[0]) < 70 && '"' !== substr($lines[0], -1)) {
-            return $description . static::escapeQuote($lines[0]) . "\"\"\"\n";
-        }
-
-        // Format a multi-line block quote to account for leading space.
-        $hasLeadingSpace = isset($lines[0]) && \in_array(substr($lines[0], 0, 1), [' ', '\t'], true);
-
-        if (!$hasLeadingSpace) {
-            $description .= "\n";
-        }
-
-        $lineLength = \count($lines);
-
-        for ($i = 0; $i < $lineLength; ++$i) {
-            if (0 !== $i || !$hasLeadingSpace) {
-                $description .= $indentation;
-            }
-            $description .= static::escapeQuote($lines[$i]) . "\n";
-        }
-
-        $description .= $indentation . "\"\"\"\n";
-
-        return $description;
-    }
-
-    /**
-     * @return string[]
-     */
-    protected static function descriptionLines(string $description, int $maxLen): array
-    {
-        $lines = [];
-        $rawLines = explode("\n", $description);
-
-        foreach ($rawLines as $line) {
-            if ('' === $line) {
-                $lines[] = $line;
-            } else {
-                // For > 120 character long lines, cut at space boundaries into sublines
-                // of ~80 chars.
-                $sublines = static::breakLine($line, $maxLen);
-
-                foreach ($sublines as $subline) {
-                    $lines[] = $subline;
-                }
-            }
-        }
-
-        return $lines;
-    }
-
-    /**
-     * @return string[]
-     */
-    protected static function breakLine(string $line, int $maxLen): array
-    {
-        if (\strlen($line) < $maxLen + 5) {
-            return [$line];
-        }
-
-        preg_match_all('/((?: |^).{15,' . ($maxLen - 40) . '}(?= |$))/', $line, $parts);
-
-        $parts = $parts[0];
-
-        return array_map('trim', $parts);
-    }
-
-    /**
-     * @param string[] $lines
-     */
-    protected static function printDescriptionWithComments(array $lines, string $indentation, bool $firstInBlock): string
-    {
-        $description = $indentation && !$firstInBlock ? "\n" : '';
-
-        foreach ($lines as $line) {
-            if ('' === $line) {
-                $description .= $indentation . "#\n";
-            } else {
-                $description .= $indentation . '# ' . $line . "\n";
-            }
-        }
-
-        return $description;
-    }
-
-    protected static function escapeQuote(string $line): string
-    {
-        return str_replace('"""', '\\"""', $line);
-    }
-
-    /**
-     * @param bool[]               $options
-     * @param FieldArgument[]|null $args
-     */
-    protected static function printArgs(array $options, $args, string $indentation = ''): string
-    {
-        if (!$args) {
-            return '';
-        }
-
-        // If every arg does not have a description, print them on one line.
-        if (
-            Utils::every($args, static function ($arg) {
-                return empty($arg->description);
-            })
-        ) {
-            return '(' . implode(', ', array_map('static::printInputValue', $args)) . ')';
-        }
-
-        return sprintf(
-            "(\n%s\n%s)",
-            implode(
-                "\n",
-                array_map(
-                    static function (FieldArgument $arg, $i) use ($indentation, $options): string {
-                        return static::printDescription($options, $arg, '  ' . $indentation, !$i) .
-                            '  ' .
-                            $indentation .
-                            static::printInputValue($arg);
-                    },
-                    $args,
-                    array_keys($args)
-                )
-            ),
-            $indentation
-        );
-    }
-
-    /**
-     * @param InputObjectField|FieldArgument $arg
-     */
-    protected static function printInputValue($arg): string
-    {
-        $argDecl = $arg->name . ': ' . (string) $arg->getType();
-
-        if ($arg->defaultValueExists()) {
-            $argDecl .= ' = ' . Printer::doPrint(AST::astFromValue($arg->defaultValue, $arg->getType()));
-        }
-
-        return $argDecl;
-    }
-
     /**
      * @param array<string, bool> $options
      */
     public static function printType(Type $type, array $options = []): string
     {
-        if ($type instanceof ScalarType) {
-            if (FederatedSchema::RESERVED_TYPE_ANY !== $type->name) {
-                return static::printScalar($type, $options);
-            }
-
-            return '';
-        }
-
-        if ($type instanceof EntityObjectType || $type instanceof EntityRefObjectType) {
+        if ($type instanceof EntityObjectType /* || $type instanceof EntityRefObjectType */) {
             return static::printEntityObject($type, $options);
         }
 
-        if ($type instanceof ObjectType) {
-            if (FederatedSchema::RESERVED_TYPE_SERVICE !== $type->name) {
-                return static::printObject($type, $options);
-            }
-
-            return '';
-        }
-
-        if ($type instanceof InterfaceType) {
-            return static::printInterface($type, $options);
-        }
-
-        if ($type instanceof UnionType) {
-            if (FederatedSchema::RESERVED_TYPE_ENTITY !== $type->name) {
-                return static::printUnion($type, $options);
-            }
-
+        if (($type instanceof ScalarType && FederatedSchema::RESERVED_TYPE_ANY === $type->name)
+            || ($type instanceof ObjectType && FederatedSchema::RESERVED_TYPE_SERVICE === $type->name)
+            || ($type instanceof UnionType && FederatedSchema::RESERVED_TYPE_ENTITY === $type->name)) {
             return '';
         }
 
-        if ($type instanceof EnumType) {
-            return static::printEnum($type, $options);
-        }
-
-        if ($type instanceof InputObjectType) {
-            return static::printInputObject($type, $options);
-        }
-
-        throw new Error(sprintf('Unknown type: %s.', Utils::printSafe($type)));
-    }
-
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printScalar(ScalarType $type, array $options): string
-    {
-        return sprintf('%sscalar %s', static::printDescription($options, $type), $type->name);
+        return parent::printType($type, $options);
     }
 
     /**
@@ -434,9 +176,9 @@ protected static function printEntityObject(EntityObjectType $type, array $optio
 
     /**
      * @param array<string, bool> $options
-     * @param EntityObjectType|InterfaceType|ObjectType $type
+     * @param EntityObjectType|InterfaceType|ObjectType|TypeWithFields $type
      */
-    protected static function printFields(array $options, TypeWithFields $type): string
+    protected static function printFields(array $options, $type): string
     {
         $fields = array_values($type->getFields());
 
@@ -467,22 +209,6 @@ static function (FieldDefinition $f, $i) use ($options) {
         );
     }
 
-    /**
-     * @param EnumValueDefinition|FieldDefinition $fieldOrEnumVal
-     */
-    protected static function printDeprecated($fieldOrEnumVal): string
-    {
-        $reason = $fieldOrEnumVal->deprecationReason;
-        if (empty($reason)) {
-            return '';
-        }
-        if ('' === $reason || Directive::DEFAULT_DEPRECATION_REASON === $reason) {
-            return ' @deprecated';
-        }
-
-        return ' @deprecated(reason: ' . Printer::doPrint(AST::astFromValue($reason, Type::string())) . ')';
-    }
-
     protected static function printFieldFederatedDirectives(FieldDefinition $field): string
     {
         $directives = [];
@@ -504,15 +230,6 @@ protected static function printFieldFederatedDirectives(FieldDefinition $field):
         return implode(' ', $directives);
     }
 
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printInterface(InterfaceType $type, array $options): string
-    {
-        return static::printDescription($options, $type) .
-            sprintf("interface %s {\n%s\n}", $type->name, static::printFields($options, $type));
-    }
-
     /**
      * Print simple and compound primary key fields
      * {@see https://www.apollographql.com/docs/federation/v1/entities#compound-primary-keys }.
@@ -534,82 +251,4 @@ protected static function printKeyFields($keyFields): string
 
         return implode(' ', $parts);
     }
-
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printUnion(UnionType $type, array $options): string
-    {
-        return static::printDescription($options, $type) .
-            sprintf('union %s = %s', $type->name, implode(' | ', $type->getTypes()));
-    }
-
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printEnum(EnumType $type, array $options): string
-    {
-        return static::printDescription($options, $type) .
-            sprintf("enum %s {\n%s\n}", $type->name, static::printEnumValues($type->getValues(), $options));
-    }
-
-    /**
-     * @param EnumValueDefinition[] $values
-     * @param array<string, bool> $options
-     */
-    protected static function printEnumValues(array $values, array $options): string
-    {
-        return implode(
-            "\n",
-            array_map(
-                static function ($value, $i) use ($options) {
-                    return static::printDescription($options, $value, '  ', !$i) .
-                        '  ' .
-                        $value->name .
-                        static::printDeprecated($value);
-                },
-                $values,
-                array_keys($values)
-            )
-        );
-    }
-
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printInputObject(InputObjectType $type, array $options): string
-    {
-        $fields = array_values($type->getFields());
-
-        return static::printDescription($options, $type) .
-            sprintf(
-                "input %s {\n%s\n}",
-                $type->name,
-                implode(
-                    "\n",
-                    array_map(
-                        static function ($f, $i) use ($options) {
-                            return static::printDescription($options, $f, '  ', !$i) . '  ' . static::printInputValue($f);
-                        },
-                        $fields,
-                        array_keys($fields)
-                    )
-                )
-            );
-    }
-
-    /**
-     * @param array<string, bool> $options
-     *
-     * @api
-     */
-    public static function printIntrospectionSchema(Schema $schema, array $options = []): string
-    {
-        return static::printFilteredSchema(
-            $schema,
-            [Directive::class, 'isSpecifiedDirective'],
-            [Introspection::class, 'isIntrospectionType'],
-            $options
-        );
-    }
 }

From 5077032875d4a4fa3e9b910fdbb73afe13343ca5 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 10:09:35 +0300
Subject: [PATCH 14/40] Reduce copy-paste & fix code style

---
 composer.json                        |  2 +-
 composer.lock                        | 67 +++++++++++++---------------
 src/Utils/FederatedSchemaPrinter.php | 62 ++++++++++++-------------
 3 files changed, 61 insertions(+), 70 deletions(-)

diff --git a/composer.json b/composer.json
index 1c12db3..9f615c0 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "type": "library",
     "license": "MIT",
     "require": {
-        "php": "^7.1||^8.0",
+        "php": "^7.4||^8.0",
         "webonyx/graphql-php": "^0.13.8 || ^14.0"
     },
     "scripts": {
diff --git a/composer.lock b/composer.lock
index 6aaf28b..2d31147 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "88c069015f1fba351e03821fd8011767",
+    "content-hash": "31bbd417e676ab9e2fa653e55383f263",
     "packages": [
         {
             "name": "webonyx/graphql-php",
@@ -160,9 +160,6 @@
             "require": {
                 "php": "^7.1 || ^8.0"
             },
-            "replace": {
-                "myclabs/deep-copy": "self.version"
-            },
             "require-dev": {
                 "doctrine/collections": "^1.0",
                 "doctrine/common": "^2.6",
@@ -170,12 +167,12 @@
             },
             "type": "library",
             "autoload": {
-                "psr-4": {
-                    "DeepCopy\\": "src/DeepCopy/"
-                },
                 "files": [
                     "src/DeepCopy/deep_copy.php"
-                ]
+                ],
+                "psr-4": {
+                    "DeepCopy\\": "src/DeepCopy/"
+                }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
@@ -1006,12 +1003,12 @@
             },
             "type": "library",
             "autoload": {
-                "psr-4": {
-                    "React\\Promise\\": "src/"
-                },
                 "files": [
                     "src/functions_include.php"
-                ]
+                ],
+                "psr-4": {
+                    "React\\Promise\\": "src/"
+                }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
@@ -1927,12 +1924,12 @@
                 }
             },
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Polyfill\\Ctype\\": ""
-                },
                 "files": [
                     "bootstrap.php"
-                ]
+                ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Ctype\\": ""
+                }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
@@ -2006,12 +2003,12 @@
                 }
             },
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Polyfill\\Intl\\Grapheme\\": ""
-                },
                 "files": [
                     "bootstrap.php"
-                ]
+                ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Intl\\Grapheme\\": ""
+                }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
@@ -2087,12 +2084,12 @@
                 }
             },
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Polyfill\\Intl\\Normalizer\\": ""
-                },
                 "files": [
                     "bootstrap.php"
                 ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Intl\\Normalizer\\": ""
+                },
                 "classmap": [
                     "Resources/stubs"
                 ]
@@ -2171,12 +2168,12 @@
                 }
             },
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Polyfill\\Mbstring\\": ""
-                },
                 "files": [
                     "bootstrap.php"
-                ]
+                ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Mbstring\\": ""
+                }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
@@ -2248,12 +2245,12 @@
                 }
             },
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Polyfill\\Php80\\": ""
-                },
                 "files": [
                     "bootstrap.php"
                 ],
+                "psr-4": {
+                    "Symfony\\Polyfill\\Php80\\": ""
+                },
                 "classmap": [
                     "Resources/stubs"
                 ]
@@ -2606,12 +2603,12 @@
             },
             "type": "library",
             "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\String\\": ""
-                },
                 "files": [
                     "Resources/functions.php"
                 ],
+                "psr-4": {
+                    "Symfony\\Component\\String\\": ""
+                },
                 "exclude-from-classmap": [
                     "/Tests/"
                 ]
@@ -2849,8 +2846,8 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "^7.1||^8.0"
+        "php": "^7.4||^8.0"
     },
     "platform-dev": [],
-    "plugin-api-version": "2.1.0"
+    "plugin-api-version": "2.3.0"
 }
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 096291d..14ea4d2 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -71,12 +71,8 @@ public static function doPrint(Schema $schema, array $options = []): string
     {
         return static::printFilteredSchema(
             $schema,
-            static function (Directive $type): bool {
-                return !Directive::isSpecifiedDirective($type) && !static::isFederatedDirective($type);
-            },
-            static function (Type $type): bool {
-                return !Type::isBuiltInType($type);
-            },
+            static fn (Directive $type): bool => !Directive::isSpecifiedDirective($type) && !static::isFederatedDirective($type),
+            static fn (Type $type): bool => !Type::isBuiltInType($type),
             $options
         );
     }
@@ -113,16 +109,7 @@ protected static function printObject(ObjectType $type, array $options): string
             return '';
         }
 
-        $interfaces = $type->getInterfaces();
-        $implementedInterfaces = !empty($interfaces)
-            ? ' implements ' .
-                implode(
-                    ' & ',
-                    array_map(static function ($i) {
-                        return $i->name;
-                    }, $interfaces)
-                )
-            : '';
+        $implementedInterfaces = static::printImplementedInterfaces($type);
 
         $queryExtends = \in_array($type->name, [FederatedSchema::RESERVED_TYPE_QUERY, FederatedSchema::RESERVED_TYPE_MUTATION], true)
             ? 'extend '
@@ -143,22 +130,8 @@ protected static function printObject(ObjectType $type, array $options): string
      */
     protected static function printEntityObject(EntityObjectType $type, array $options): string
     {
-        $interfaces = $type->getInterfaces();
-        $implementedInterfaces = !empty($interfaces)
-            ? ' implements ' .
-                implode(
-                    ' & ',
-                    array_map(static function ($i) {
-                        return $i->name;
-                    }, $interfaces)
-                )
-            : '';
-
-        $keyDirective = '';
-
-        foreach ($type->getKeyFields() as $keyField) {
-            $keyDirective = $keyDirective . sprintf(' @key(fields: "%s")', static::printKeyFields($keyField));
-        }
+        $implementedInterfaces = static::printImplementedInterfaces($type);
+        $keyDirective = static::printKeyDirective($type);
 
         $isEntityRef = $type instanceof EntityRefObjectType;
         $extends = $isEntityRef ? 'extend ' : '';
@@ -184,8 +157,9 @@ protected static function printFields(array $options, $type): string
 
         if (FederatedSchema::RESERVED_TYPE_QUERY === $type->name) {
             $fields = array_filter($fields, static function (FieldDefinition $field): bool {
-                return FederatedSchema::RESERVED_FIELD_SERVICE !== $field->name
-                    && FederatedSchema::RESERVED_FIELD_ENTITIES !== $field->name;
+                $excludedFields = [FederatedSchema::RESERVED_FIELD_SERVICE, FederatedSchema::RESERVED_FIELD_ENTITIES];
+
+                return !\in_array($field->name, $excludedFields, true);
             });
         }
 
@@ -230,6 +204,26 @@ protected static function printFieldFederatedDirectives(FieldDefinition $field):
         return implode(' ', $directives);
     }
 
+    protected static function printImplementedInterfaces(ObjectType $type): string
+    {
+        $interfaces = $type->getInterfaces();
+
+        return !empty($interfaces)
+            ? ' implements ' . implode(' & ', array_map(static fn (InterfaceType $i): string => $i->name, $interfaces))
+            : '';
+    }
+
+    protected static function printKeyDirective(EntityObjectType $type): string
+    {
+        $keyDirective = '';
+
+        foreach ($type->getKeyFields() as $keyField) {
+            $keyDirective .= sprintf(' @key(fields: "%s")', static::printKeyFields($keyField));
+        }
+
+        return $keyDirective;
+    }
+
     /**
      * Print simple and compound primary key fields
      * {@see https://www.apollographql.com/docs/federation/v1/entities#compound-primary-keys }.

From d23332d062d7c031c8a61babc6b5cfac183ebf07 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 10:21:46 +0300
Subject: [PATCH 15/40] Refactor code to make more readable

---
 src/FederatedSchema.php              |  5 +++++
 src/Utils/FederatedSchemaPrinter.php | 11 +++--------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 757109e..0530afd 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -74,6 +74,11 @@ class FederatedSchema extends Schema
     /** @var Directive[] */
     protected $entityDirectives;
 
+    public static function isReservedRootType(string $name): bool
+    {
+        return \in_array($name, [self::RESERVED_TYPE_QUERY, self::RESERVED_TYPE_MUTATION], true);
+    }
+
     /**
      * @param array<string,mixed> $config
      */
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 14ea4d2..035864d 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -110,15 +110,12 @@ protected static function printObject(ObjectType $type, array $options): string
         }
 
         $implementedInterfaces = static::printImplementedInterfaces($type);
-
-        $queryExtends = \in_array($type->name, [FederatedSchema::RESERVED_TYPE_QUERY, FederatedSchema::RESERVED_TYPE_MUTATION], true)
-            ? 'extend '
-            : '';
+        $extends = FederatedSchema::isReservedRootType($type->name) ? 'extend ' : '';
 
         return static::printDescription($options, $type) .
             sprintf(
                 "%stype %s%s {\n%s\n}",
-                $queryExtends,
+                $extends,
                 $type->name,
                 $implementedInterfaces,
                 static::printFields($options, $type)
@@ -132,9 +129,7 @@ protected static function printEntityObject(EntityObjectType $type, array $optio
     {
         $implementedInterfaces = static::printImplementedInterfaces($type);
         $keyDirective = static::printKeyDirective($type);
-
-        $isEntityRef = $type instanceof EntityRefObjectType;
-        $extends = $isEntityRef ? 'extend ' : '';
+        $extends = $type instanceof EntityRefObjectType ? 'extend ' : '';
 
         return static::printDescription($options, $type) .
             sprintf(

From 5724b2c038a0f610ea10c386c635a45a67d6e56b Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 10:25:55 +0300
Subject: [PATCH 16/40] Fix code style

---
 src/Directives.php                   | 14 +++++++-------
 src/Directives/ExternalDirective.php |  2 +-
 src/Directives/KeyDirective.php      | 10 +++++-----
 src/Directives/ProvidesDirective.php | 10 +++++-----
 src/Directives/RequiresDirective.php | 10 +++++-----
 5 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/src/Directives.php b/src/Directives.php
index 8ee46ca..ec21a05 100644
--- a/src/Directives.php
+++ b/src/Directives.php
@@ -4,8 +4,8 @@
 
 namespace Apollo\Federation;
 
-use Apollo\Federation\Directives\KeyDirective;
 use Apollo\Federation\Directives\ExternalDirective;
+use Apollo\Federation\Directives\KeyDirective;
 use Apollo\Federation\Directives\ProvidesDirective;
 use Apollo\Federation\Directives\RequiresDirective;
 use Apollo\Federation\Enum\DirectiveEnum;
@@ -20,7 +20,7 @@ class Directives
     private static $directives = null;
 
     /**
-     * Gets the @key directive
+     * Gets the @key directive.
      */
     public static function key(): KeyDirective
     {
@@ -28,7 +28,7 @@ public static function key(): KeyDirective
     }
 
     /**
-     * Gets the @external directive
+     * Gets the @external directive.
      */
     public static function external(): ExternalDirective
     {
@@ -36,7 +36,7 @@ public static function external(): ExternalDirective
     }
 
     /**
-     * Gets the @requires directive
+     * Gets the @requires directive.
      */
     public static function requires(): RequiresDirective
     {
@@ -44,7 +44,7 @@ public static function requires(): RequiresDirective
     }
 
     /**
-     * Gets the @provides directive
+     * Gets the @provides directive.
      */
     public static function provides(): ProvidesDirective
     {
@@ -52,7 +52,7 @@ public static function provides(): ProvidesDirective
     }
 
     /**
-     * Gets the directives that can be used on federated entity types
+     * Gets the directives that can be used on federated entity types.
      *
      * @return array<string,Directive>
      */
@@ -60,8 +60,8 @@ public static function getDirectives(): array
     {
         if (!self::$directives) {
             self::$directives = [
-                DirectiveEnum::KEY => new KeyDirective(),
                 DirectiveEnum::EXTERNAL => new ExternalDirective(),
+                DirectiveEnum::KEY => new KeyDirective(),
                 DirectiveEnum::REQUIRES => new RequiresDirective(),
                 DirectiveEnum::PROVIDES => new ProvidesDirective(),
             ];
diff --git a/src/Directives/ExternalDirective.php b/src/Directives/ExternalDirective.php
index 7a837b5..3c8d024 100644
--- a/src/Directives/ExternalDirective.php
+++ b/src/Directives/ExternalDirective.php
@@ -17,7 +17,7 @@ public function __construct()
     {
         parent::__construct([
             'name' => DirectiveEnum::EXTERNAL,
-            'locations' => [DirectiveLocation::FIELD_DEFINITION]
+            'locations' => [DirectiveLocation::FIELD_DEFINITION],
         ]);
     }
 }
diff --git a/src/Directives/KeyDirective.php b/src/Directives/KeyDirective.php
index 08623d8..4129547 100644
--- a/src/Directives/KeyDirective.php
+++ b/src/Directives/KeyDirective.php
@@ -3,10 +3,10 @@
 namespace Apollo\Federation\Directives;
 
 use Apollo\Federation\Enum\DirectiveEnum;
-use GraphQL\Type\Definition\Type;
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
-use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Type;
 
 /**
  * The `@key` directive is used to indicate a combination of fields that can be used to uniquely
@@ -22,9 +22,9 @@ public function __construct()
             'args' => [
                 new FieldArgument([
                     'name' => 'fields',
-                    'type' => Type::nonNull(Type::string())
-                ])
-            ]
+                    'type' => Type::nonNull(Type::string()),
+                ]),
+            ],
         ]);
     }
 }
diff --git a/src/Directives/ProvidesDirective.php b/src/Directives/ProvidesDirective.php
index f474cae..24d9be1 100644
--- a/src/Directives/ProvidesDirective.php
+++ b/src/Directives/ProvidesDirective.php
@@ -3,10 +3,10 @@
 namespace Apollo\Federation\Directives;
 
 use Apollo\Federation\Enum\DirectiveEnum;
-use GraphQL\Type\Definition\Type;
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
-use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Type;
 
 /**
  * The `@provides` directive is used to annotate the expected returned fieldset from a field
@@ -22,9 +22,9 @@ public function __construct()
             'args' => [
                 new FieldArgument([
                     'name' => 'fields',
-                    'type' => Type::nonNull(Type::string())
-                ])
-            ]
+                    'type' => Type::nonNull(Type::string()),
+                ]),
+            ],
         ]);
     }
 }
diff --git a/src/Directives/RequiresDirective.php b/src/Directives/RequiresDirective.php
index ab8d9e7..d33bec3 100644
--- a/src/Directives/RequiresDirective.php
+++ b/src/Directives/RequiresDirective.php
@@ -3,10 +3,10 @@
 namespace Apollo\Federation\Directives;
 
 use Apollo\Federation\Enum\DirectiveEnum;
-use GraphQL\Type\Definition\Type;
+use GraphQL\Language\DirectiveLocation;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
-use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Type;
 
 /**
  * The `@requires` directive is used to annotate the required input fieldset from a base type
@@ -23,9 +23,9 @@ public function __construct()
             'args' => [
                 new FieldArgument([
                     'name' => 'fields',
-                    'type' => Type::nonNull(Type::string())
-                ])
-            ]
+                    'type' => Type::nonNull(Type::string()),
+                ]),
+            ],
         ]);
     }
 }

From 3e217deab7dce39aaeddfd04485d444af3a84567 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 10:58:13 +0300
Subject: [PATCH 17/40] Extract FederatedSchemaTrait

---
 src/FederatedSchema.php      | 174 +------------------------------
 src/FederatedSchemaTrait.php | 195 +++++++++++++++++++++++++++++++++++
 2 files changed, 197 insertions(+), 172 deletions(-)
 create mode 100644 src/FederatedSchemaTrait.php

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 0530afd..f3b3fd4 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -56,6 +56,8 @@
  */
 class FederatedSchema extends Schema
 {
+    use FederatedSchemaTrait;
+
     public const RESERVED_TYPE_ANY = '_Any';
     public const RESERVED_TYPE_ENTITY = '_Entity';
     public const RESERVED_TYPE_SERVICE = '_Service';
@@ -68,12 +70,6 @@ class FederatedSchema extends Schema
     public const RESERVED_FIELD_SERVICE = '_service';
     public const RESERVED_FIELD_TYPE_NAME = '__typename';
 
-    /** @var EntityObjectType[] */
-    protected $entityTypes;
-
-    /** @var Directive[] */
-    protected $entityDirectives;
-
     public static function isReservedRootType(string $name): bool
     {
         return \in_array($name, [self::RESERVED_TYPE_QUERY, self::RESERVED_TYPE_MUTATION], true);
@@ -91,170 +87,4 @@ public function __construct(array $config)
 
         parent::__construct($config);
     }
-
-    /**
-     * Returns all the resolved entity types in the schema.
-     *
-     * @return EntityObjectType[]
-     */
-    public function getEntityTypes(): array
-    {
-        return $this->entityTypes;
-    }
-
-    /**
-     * Indicates whether the schema has entity types resolved.
-     */
-    public function hasEntityTypes(): bool
-    {
-        return !empty($this->getEntityTypes());
-    }
-
-    /**
-     * @param array<string,mixed> $config
-     *
-     * @return array<string,mixed>
-     */
-    private function getEntityDirectivesConfig(array $config): array
-    {
-        $directives = isset($config['directives']) ? $config['directives'] : [];
-        $config['directives'] = array_merge($directives, $this->entityDirectives);
-
-        return $config;
-    }
-
-    /**
-     * @param array<string,mixed> $config
-     *
-     * @return array{ query: ObjectType }
-     */
-    private function getQueryTypeConfig(array $config): array
-    {
-        $queryTypeConfig = $config['query']->config;
-        if (\is_callable($queryTypeConfig['fields'])) {
-            $queryTypeConfig['fields'] = $queryTypeConfig['fields']();
-        }
-
-        $queryTypeConfig['fields'] = array_merge(
-            $queryTypeConfig['fields'],
-            $this->getQueryTypeServiceFieldConfig(),
-            $this->getQueryTypeEntitiesFieldConfig($config)
-        );
-
-        return [
-            'query' => new ObjectType($queryTypeConfig),
-        ];
-    }
-
-    /**
-     * @return array{ _service: array<string,mixed> }
-     */
-    private function getQueryTypeServiceFieldConfig(): array
-    {
-        $serviceType = new ObjectType([
-            'name' => self::RESERVED_TYPE_SERVICE,
-            'fields' => [
-                self::RESERVED_FIELD_SDL => [
-                    'type' => Type::string(),
-                    'resolve' => function () {
-                        return FederatedSchemaPrinter::doPrint($this);
-                    },
-                ],
-            ],
-        ]);
-
-        return [
-            self::RESERVED_FIELD_SERVICE => [
-                'type' => Type::nonNull($serviceType),
-                'resolve' => function () {
-                    return [];
-                },
-            ],
-        ];
-    }
-
-    /**
-     * @param array<string,mixed>|null $config
-     *
-     * @return array<string,array{ type: ListOfType, args: array<string,array<string,Type>>, resolve: callable }>
-     */
-    private function getQueryTypeEntitiesFieldConfig(?array $config): array
-    {
-        if (!$this->hasEntityTypes()) {
-            return [];
-        }
-
-        $entityType = new UnionType([
-            'name' => self::RESERVED_TYPE_ENTITY,
-            'types' => array_values($this->getEntityTypes()),
-        ]);
-
-        $anyType = new CustomScalarType([
-            'name' => self::RESERVED_TYPE_ANY,
-            'serialize' => function ($value) {
-                return $value;
-            },
-        ]);
-
-        return [
-            self::RESERVED_FIELD_ENTITIES => [
-                'type' => Type::listOf($entityType),
-                'args' => [
-                    self::RESERVED_FIELD_REPRESENTATIONS => [
-                        'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType))),
-                    ],
-                ],
-                'resolve' => function ($root, $args, $context, $info) use ($config) {
-                    if ($config && isset($config['resolve']) && \is_callable($config['resolve'])) {
-                        return $config['resolve']($root, $args, $context, $info);
-                    }
-
-                    return $this->resolve($root, $args, $context, $info);
-                },
-            ],
-        ];
-    }
-
-    private function resolve($root, $args, $context, $info): array
-    {
-        return array_map(static function ($ref) use ($context, $info) {
-            Utils::invariant(isset($ref[self::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
-
-            $typeName = $ref[self::RESERVED_FIELD_TYPE_NAME];
-            $type = $info->schema->getType($typeName);
-
-            Utils::invariant(
-                $type && $type instanceof EntityObjectType,
-                sprintf(
-                    'The _entities resolver tried to load an entity for type "%s", but no object type of that name was found in the schema',
-                    $type->name
-                )
-            );
-
-            if (!$type->hasReferenceResolver()) {
-                return $ref;
-            }
-
-            return $type->resolveReference($ref, $context, $info);
-        }, $args[self::RESERVED_FIELD_REPRESENTATIONS]);
-    }
-
-    /**
-     * @param array<string,mixed> $config
-     *
-     * @return EntityObjectType[]
-     */
-    private function extractEntityTypes(array $config): array
-    {
-        $resolvedTypes = TypeInfo::extractTypes($config['query']);
-        $entityTypes = [];
-
-        foreach ($resolvedTypes as $type) {
-            if ($type instanceof EntityObjectType) {
-                $entityTypes[$type->name] = $type;
-            }
-        }
-
-        return $entityTypes;
-    }
 }
diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
new file mode 100644
index 0000000..cc57ebc
--- /dev/null
+++ b/src/FederatedSchemaTrait.php
@@ -0,0 +1,195 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation;
+
+use Apollo\Federation\Types\EntityObjectType;
+use Apollo\Federation\Utils\FederatedSchemaPrinter;
+use GraphQL\Type\Definition\CustomScalarType;
+use GraphQL\Type\Definition\Directive;
+use GraphQL\Type\Definition\ListOfType;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Definition\UnionType;
+use GraphQL\Utils\TypeInfo;
+use GraphQL\Utils\Utils;
+
+trait FederatedSchemaTrait
+{
+    /**
+     * @var EntityObjectType[]
+     */
+    protected array $entityTypes = [];
+
+    /**
+     * @var Directive[]
+     */
+    protected array $entityDirectives = [];
+
+    /**
+     * Returns all the resolved entity types in the schema.
+     *
+     * @return EntityObjectType[]
+     */
+    public function getEntityTypes(): array
+    {
+        return $this->entityTypes;
+    }
+
+    /**
+     * Indicates whether the schema has entity types resolved.
+     */
+    public function hasEntityTypes(): bool
+    {
+        return !empty($this->getEntityTypes());
+    }
+
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return array<string,mixed>
+     */
+    protected function getEntityDirectivesConfig(array $config): array
+    {
+        $directives = $config['directives'] ?? [];
+        $config['directives'] = array_merge($directives, $this->entityDirectives);
+
+        return $config;
+    }
+
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return array{ query: ObjectType }
+     */
+    protected function getQueryTypeConfig(array $config): array
+    {
+        $queryTypeConfig = $config['query']->config;
+        if (\is_callable($queryTypeConfig['fields'])) {
+            $queryTypeConfig['fields'] = $queryTypeConfig['fields']();
+        }
+
+        $queryTypeConfig['fields'] = array_merge(
+            $queryTypeConfig['fields'],
+            $this->getQueryTypeServiceFieldConfig(),
+            $this->getQueryTypeEntitiesFieldConfig($config)
+        );
+
+        return [
+            'query' => new ObjectType($queryTypeConfig),
+        ];
+    }
+
+    /**
+     * @return array{ _service: array<string,mixed> }
+     */
+    protected function getQueryTypeServiceFieldConfig(): array
+    {
+        $serviceType = new ObjectType([
+            'name' => self::RESERVED_TYPE_SERVICE,
+            'fields' => [
+                self::RESERVED_FIELD_SDL => [
+                    'type' => Type::string(),
+                    'resolve' => function () {
+                        return FederatedSchemaPrinter::doPrint($this);
+                    },
+                ],
+            ],
+        ]);
+
+        return [
+            self::RESERVED_FIELD_SERVICE => [
+                'type' => Type::nonNull($serviceType),
+                'resolve' => function () {
+                    return [];
+                },
+            ],
+        ];
+    }
+
+    /**
+     * @param array<string,mixed>|null $config
+     *
+     * @return array<string,array{ type: ListOfType, args: array<string,array<string,Type>>, resolve: callable }>
+     */
+    protected function getQueryTypeEntitiesFieldConfig(?array $config): array
+    {
+        if (!$this->hasEntityTypes()) {
+            return [];
+        }
+
+        $entityType = new UnionType([
+            'name' => self::RESERVED_TYPE_ENTITY,
+            'types' => array_values($this->getEntityTypes()),
+        ]);
+
+        $anyType = new CustomScalarType([
+            'name' => self::RESERVED_TYPE_ANY,
+            'serialize' => function ($value) {
+                return $value;
+            },
+        ]);
+
+        return [
+            self::RESERVED_FIELD_ENTITIES => [
+                'type' => Type::listOf($entityType),
+                'args' => [
+                    self::RESERVED_FIELD_REPRESENTATIONS => [
+                        'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType))),
+                    ],
+                ],
+                'resolve' => function ($root, $args, $context, $info) use ($config) {
+                    if ($config && isset($config['resolve']) && \is_callable($config['resolve'])) {
+                        return $config['resolve']($root, $args, $context, $info);
+                    }
+
+                    return $this->resolve($root, $args, $context, $info);
+                },
+            ],
+        ];
+    }
+
+    protected function resolve($root, $args, $context, $info): array
+    {
+        return array_map(static function ($ref) use ($context, $info) {
+            Utils::invariant(isset($ref[self::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
+
+            $typeName = $ref[self::RESERVED_FIELD_TYPE_NAME];
+            $type = $info->schema->getType($typeName);
+
+            Utils::invariant(
+                $type && $type instanceof EntityObjectType,
+                sprintf(
+                    'The _entities resolver tried to load an entity for type "%s", but no object type of that name was found in the schema',
+                    $type->name
+                )
+            );
+
+            if (!$type->hasReferenceResolver()) {
+                return $ref;
+            }
+
+            return $type->resolveReference($ref, $context, $info);
+        }, $args[self::RESERVED_FIELD_REPRESENTATIONS]);
+    }
+
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return EntityObjectType[]
+     */
+    protected function extractEntityTypes(array $config): array
+    {
+        $resolvedTypes = TypeInfo::extractTypes($config['query']);
+        $entityTypes = [];
+
+        foreach ($resolvedTypes as $type) {
+            if ($type instanceof EntityObjectType) {
+                $entityTypes[$type->name] = $type;
+            }
+        }
+
+        return $entityTypes;
+    }
+}

From 4a21ab5338d873bfd696b4903e64597648b6f6b4 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 11:22:06 +0300
Subject: [PATCH 18/40] Fix code style

---
 src/FederatedSchemaTrait.php | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index cc57ebc..5afbffe 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -91,9 +91,7 @@ protected function getQueryTypeServiceFieldConfig(): array
             'fields' => [
                 self::RESERVED_FIELD_SDL => [
                     'type' => Type::string(),
-                    'resolve' => function () {
-                        return FederatedSchemaPrinter::doPrint($this);
-                    },
+                    'resolve' => fn (): string => FederatedSchemaPrinter::doPrint($this),
                 ],
             ],
         ]);
@@ -101,9 +99,7 @@ protected function getQueryTypeServiceFieldConfig(): array
         return [
             self::RESERVED_FIELD_SERVICE => [
                 'type' => Type::nonNull($serviceType),
-                'resolve' => function () {
-                    return [];
-                },
+                'resolve' => static fn (): array => [],
             ],
         ];
     }
@@ -126,9 +122,7 @@ protected function getQueryTypeEntitiesFieldConfig(?array $config): array
 
         $anyType = new CustomScalarType([
             'name' => self::RESERVED_TYPE_ANY,
-            'serialize' => function ($value) {
-                return $value;
-            },
+            'serialize' => static fn ($value) => $value,
         ]);
 
         return [

From 8ad004784e345b74e12b2be970b29ac03ff0a3ed Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 11:22:17 +0300
Subject: [PATCH 19/40] Fix tests code style

---
 test/DirectivesTest.php | 16 ++++----
 test/EntitiesTest.php   | 26 ++++++------
 test/SchemaTest.php     | 30 +++++++-------
 test/StarWarsData.php   | 88 ++++++++++++++++++++++++++---------------
 test/StarWarsSchema.php | 83 ++++++++++++++++++--------------------
 5 files changed, 131 insertions(+), 112 deletions(-)

diff --git a/test/DirectivesTest.php b/test/DirectivesTest.php
index 474e477..7023c6f 100644
--- a/test/DirectivesTest.php
+++ b/test/DirectivesTest.php
@@ -17,7 +17,7 @@ class DirectivesTest extends TestCase
 {
     use MatchesSnapshots;
 
-    public function testKeyDirective()
+    public function testKeyDirective(): void
     {
         $config = Directives::key()->config;
 
@@ -27,7 +27,7 @@ public function testKeyDirective()
         $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
     }
 
-    public function testExternalDirective()
+    public function testExternalDirective(): void
     {
         $config = Directives::external()->config;
 
@@ -37,7 +37,7 @@ public function testExternalDirective()
         $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
     }
 
-    public function testRequiresDirective()
+    public function testRequiresDirective(): void
     {
         $config = Directives::requires()->config;
 
@@ -47,7 +47,7 @@ public function testRequiresDirective()
         $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
     }
 
-    public function testProvidesDirective()
+    public function testProvidesDirective(): void
     {
         $config = Directives::provides()->config;
 
@@ -57,16 +57,16 @@ public function testProvidesDirective()
         $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
     }
 
-    public function testItAddsDirectivesToSchema()
+    public function testItAddsDirectivesToSchema(): void
     {
         $schema = new Schema([
             'query' => new ObjectType([
                 'name' => 'Query',
                 'fields' => [
-                    '_' => ['type' => Type::string()]
-                ]
+                    '_' => ['type' => Type::string()],
+                ],
             ]),
-            'directives' => Directives::getDirectives()
+            'directives' => Directives::getDirectives(),
         ]);
 
         $schemaSdl = SchemaPrinter::doPrint($schema);
diff --git a/test/EntitiesTest.php b/test/EntitiesTest.php
index 2acb5d5..e0e51ec 100644
--- a/test/EntitiesTest.php
+++ b/test/EntitiesTest.php
@@ -14,7 +14,7 @@ class EntitiesTest extends TestCase
 {
     use MatchesSnapshots;
 
-    public function testCreatingEntityType()
+    public function testCreatingEntityType(): void
     {
         $userTypeKeyFields = ['id', 'email'];
 
@@ -25,15 +25,15 @@ public function testCreatingEntityType()
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
                 'firstName' => ['type' => Type::string()],
-                'lastName' => ['type' => Type::string()]
-            ]
+                'lastName' => ['type' => Type::string()],
+            ],
         ]);
 
         $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
         $this->assertMatchesSnapshot($userType->config);
     }
 
-    public function testCreatingEntityTypeWithCallable()
+    public function testCreatingEntityTypeWithCallable(): void
     {
         $userTypeKeyFields = ['id', 'email'];
 
@@ -45,23 +45,23 @@ public function testCreatingEntityTypeWithCallable()
                     'id' => ['type' => Type::int()],
                     'email' => ['type' => Type::string()],
                     'firstName' => ['type' => Type::string()],
-                    'lastName' => ['type' => Type::string()]
+                    'lastName' => ['type' => Type::string()],
                 ];
-            }
+            },
         ]);
 
         $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
         $this->assertMatchesSnapshot($userType->config);
     }
 
-    public function testResolvingEntityReference()
+    public function testResolvingEntityReference(): void
     {
         $expectedRef = [
             'id' => 1,
             'email' => 'luke@skywalker.com',
             'firstName' => 'Luke',
             'lastName' => 'Skywalker',
-            '__typename' => 'User'
+            '__typename' => 'User',
         ];
 
         $userType = new EntityObjectType([
@@ -71,11 +71,11 @@ public function testResolvingEntityReference()
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
                 'firstName' => ['type' => Type::string()],
-                'lastName' => ['type' => Type::string()]
+                'lastName' => ['type' => Type::string()],
             ],
             '__resolveReference' => function () use ($expectedRef) {
                 return $expectedRef;
-            }
+            },
         ]);
 
         $actualRef = $userType->resolveReference(['id' => 1, 'email' => 'luke@skywalker.com', '__typename' => 'User']);
@@ -83,7 +83,7 @@ public function testResolvingEntityReference()
         $this->assertEquals($expectedRef, $actualRef);
     }
 
-    public function testCreatingEntityRefType()
+    public function testCreatingEntityRefType(): void
     {
         $userTypeKeyFields = ['id', 'email'];
 
@@ -92,8 +92,8 @@ public function testCreatingEntityRefType()
             'keyFields' => $userTypeKeyFields,
             'fields' => [
                 'id' => ['type' => Type::int()],
-                'email' => ['type' => Type::string()]
-            ]
+                'email' => ['type' => Type::string()],
+            ],
         ]);
 
         $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
diff --git a/test/SchemaTest.php b/test/SchemaTest.php
index 4262bba..e18de09 100644
--- a/test/SchemaTest.php
+++ b/test/SchemaTest.php
@@ -13,7 +13,7 @@ class SchemaTest extends TestCase
 {
     use MatchesSnapshots;
 
-    public function testRunningQueries()
+    public function testRunningQueries(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
         $query = 'query GetEpisodes { episodes { id title characters { id name } } }';
@@ -23,7 +23,7 @@ public function testRunningQueries()
         $this->assertMatchesSnapshot($result->toArray());
     }
 
-    public function testEntityTypes()
+    public function testEntityTypes(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
 
@@ -36,7 +36,7 @@ public function testEntityTypes()
         $this->assertArrayHasKey('Location', $entityTypes);
     }
 
-    public function testMetaTypes()
+    public function testMetaTypes(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
 
@@ -48,7 +48,7 @@ public function testMetaTypes()
         $this->assertEqualsCanonicalizing($entitiesType->getTypes(), array_values($schema->getEntityTypes()));
     }
 
-    public function testDirectives()
+    public function testDirectives(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
         $directives = $schema->getDirectives();
@@ -59,7 +59,7 @@ public function testDirectives()
         $this->assertArrayHasKey('requires', $directives);
     }
 
-    public function testServiceSdl()
+    public function testServiceSdl(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
         $query = 'query GetServiceSdl { _service { sdl } }';
@@ -69,7 +69,7 @@ public function testServiceSdl()
         $this->assertMatchesSnapshot($result->toArray());
     }
 
-    public function testSchemaSdl()
+    public function testSchemaSdl(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
         $schemaSdl = SchemaPrinter::doPrint($schema);
@@ -77,11 +77,10 @@ public function testSchemaSdl()
         $this->assertMatchesSnapshot($schemaSdl);
     }
 
-    public function testResolvingEntityReferences()
+    public function testResolvingEntityReferences(): void
     {
         $schema = StarWarsSchema::getEpisodesSchema();
 
-
         $query = '
             query GetEpisodes($representations: [_Any!]!) {
                 _entities(representations: $representations) {
@@ -98,8 +97,8 @@ public function testResolvingEntityReferences()
                 [
                     '__typename' => 'Episode',
                     'id' => 1,
-                ]
-            ]
+                ],
+            ],
         ];
 
         $result = GraphQL::executeQuery($schema, $query, null, null, $variables);
@@ -107,7 +106,7 @@ public function testResolvingEntityReferences()
         $this->assertMatchesSnapshot($result->toArray());
     }
 
-    public function testOverrideSchemaResolver()
+    public function testOverrideSchemaResolver(): void
     {
         $schema = StarWarsSchema::getEpisodesSchemaCustomResolver();
 
@@ -126,16 +125,15 @@ public function testOverrideSchemaResolver()
             'representations' => [
                 [
                     '__typename' => 'Episode',
-                    'id' => 1
-                ]
-            ]
+                    'id' => 1,
+                ],
+            ],
         ];
 
         $result = GraphQL::executeQuery($schema, $query, null, null, $variables);
         // The custom resolver for this schema, always adds 1 to the id and gets the next
         // episode for the sake of testing the ability to change the resolver in the configuration
-        $this->assertEquals("The Empire Strikes Back", $result->data['_entities'][0]["title"]);
+        $this->assertEquals('The Empire Strikes Back', $result->data['_entities'][0]['title']);
         $this->assertMatchesSnapshot($result->toArray());
     }
 }
- 
\ No newline at end of file
diff --git a/test/StarWarsData.php b/test/StarWarsData.php
index c1cefa2..27bd28e 100644
--- a/test/StarWarsData.php
+++ b/test/StarWarsData.php
@@ -6,100 +6,126 @@
 
 class StarWarsData
 {
-    private static $episodes;
+    /**
+     * @var array<int,array<string,mixed>>|null
+     */
+    private static ?array $episodes = null;
 
-    private static $characters;
+    /**
+     * @var array<int,array<string,mixed>>|null
+     */
+    private static ?array $characters = null;
 
-    private static $locations;
+    /**
+     * @var array<int,array<string,mixed>>|null
+     */
+    private static ?array $locations = null;
 
-    public static function getEpisodeById($id)
+    /**
+     * @return array<string,mixed>|null
+     */
+    public static function getEpisodeById(int $id): ?array
     {
-        $matches = array_filter(self::getEpisodes(), function ($episode) use ($id) {
-            return $episode['id'] === $id;
-        });
-        return reset($matches);
+        $matches = array_filter(self::getEpisodes(), static fn (array $episode): bool => $episode['id'] === $id);
+
+        return reset($matches) ?: null;
     }
 
-    public static function getEpisodes()
+    /**
+     * @return array<int,array<string,mixed>>
+     */
+    public static function getEpisodes(): array
     {
         if (!self::$episodes) {
             self::$episodes = [
                 [
                     'id' => 1,
                     'title' => 'A New Hope',
-                    'characters' => [1, 2, 3]
+                    'characters' => [1, 2, 3],
                 ],
                 [
                     'id' => 2,
                     'title' => 'The Empire Strikes Back',
-                    'characters' => [1, 2, 3]
+                    'characters' => [1, 2, 3],
                 ],
                 [
                     'id' => 3,
                     'title' => 'Return of the Jedi',
-                    'characters' => [1, 2, 3]
-                ]
+                    'characters' => [1, 2, 3],
+                ],
             ];
         }
 
         return self::$episodes;
     }
 
-    public static function getCharactersByIds($ids)
+    /**
+     * @param int[] $ids
+     *
+     * @return array<int,array<string,mixed>>
+     */
+    public static function getCharactersByIds(array $ids): array
     {
-        return array_filter(self::getCharacters(), function ($character) use ($ids) {
-            return in_array($character['id'], $ids);
-        });
+        return array_filter(self::getCharacters(), static fn ($item): bool => \in_array($item['id'], $ids, true));
     }
 
-    public static function getCharacters()
+    /**
+     * @return array<int,array<string,mixed>>
+     */
+    public static function getCharacters(): array
     {
         if (!self::$characters) {
             self::$characters = [
                 [
                     'id' => 1,
                     'name' => 'Luke Skywalker',
-                    'locations' => [1, 2, 3]
+                    'locations' => [1, 2, 3],
                 ],
                 [
                     'id' => 2,
                     'name' => 'Han Solo',
-                    'locations' => [1, 2]
+                    'locations' => [1, 2],
                 ],
                 [
                     'id' => 3,
                     'name' => 'Leia Skywalker',
-                    'locations' => [3]
-                ]
+                    'locations' => [3],
+                ],
             ];
         }
 
         return self::$characters;
     }
 
-    public static function getLocationsByIds($ids)
+    /**
+     * @param int[] $ids
+     *
+     * @return array<int,array<string,mixed>>
+     */
+    public static function getLocationsByIds(array $ids): array
     {
-        return array_filter(self::getLocations(), function ($location) use ($ids) {
-            return in_array($location['id'], $ids);
-        });
+        return array_filter(self::getLocations(), static fn ($item): bool => \in_array($item['id'], $ids, true));
     }
 
-    public static function getLocations()
+    /**
+     * @return array<int,array<string,mixed>>
+     */
+    public static function getLocations(): array
     {
         if (!self::$locations) {
             self::$locations = [
                 [
                     'id' => 1,
-                    'name' => 'Tatooine'
+                    'name' => 'Tatooine',
                 ],
                 [
                     'id' => 2,
-                    'name' => 'Endor'
+                    'name' => 'Endor',
                 ],
                 [
                     'id' => 3,
-                    'name' => 'Hoth'
-                ]
+                    'name' => 'Hoth',
+                ],
             ];
         }
 
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index 9ec1f8b..6786d4b 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -4,66 +4,65 @@
 
 namespace Apollo\Federation\Tests;
 
-use GraphQL\Type\Definition\Type;
-use GraphQL\Type\Definition\ObjectType;
-
 use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
 
 class StarWarsSchema
 {
-    public static $episodesSchema;
-    public static $overRiddedEpisodesSchema;
+    public static ?FederatedSchema $episodesSchema = null;
+    public static ?FederatedSchema $overriddenEpisodesSchema = null;
 
     public static function getEpisodesSchema(): FederatedSchema
     {
         if (!self::$episodesSchema) {
             self::$episodesSchema = new FederatedSchema([
-                'query' => self::getQueryType()
+                'query' => self::getQueryType(),
             ]);
         }
+
         return self::$episodesSchema;
     }
 
     public static function getEpisodesSchemaCustomResolver(): FederatedSchema
     {
-        if (!self::$overRiddedEpisodesSchema) {
-            self::$overRiddedEpisodesSchema = new FederatedSchema([
+        if (!self::$overriddenEpisodesSchema) {
+            self::$overriddenEpisodesSchema = new FederatedSchema([
                 'query' => self::getQueryType(),
-                'resolve' =>  function ($root, $args, $context, $info) {
-                    return array_map(function ($ref) use ($info) {
+                'resolve' => function ($root, $args, $context, $info): array {
+                    return array_map(static function (array $ref) use ($info) {
                         $typeName = $ref['__typename'];
                         $type = $info->schema->getType($typeName);
-                        $ref["id"] = $ref["id"] + 1;
+                        ++$ref['id'];
+
                         return $type->resolveReference($ref);
                     }, $args[FederatedSchema::RESERVED_FIELD_REPRESENTATIONS]);
-                }
+                },
             ]);
         }
-        return self::$overRiddedEpisodesSchema;
+
+        return self::$overriddenEpisodesSchema;
     }
 
     private static function getQueryType(): ObjectType
     {
         $episodeType = self::getEpisodeType();
 
-        $queryType = new ObjectType([
+        return new ObjectType([
             'name' => FederatedSchema::RESERVED_TYPE_QUERY,
             'fields' => [
                 'episodes' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull($episodeType))),
-                    'resolve' => function () {
-                        return StarWarsData::getEpisodes();
-                    }
+                    'resolve' => static fn (): array => StarWarsData::getEpisodes(),
                 ],
                 'deprecatedEpisodes' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull($episodeType))),
-                    'deprecationReason' => 'Because you should use the other one.'
-                ]
-            ]
+                    'deprecationReason' => 'Because you should use the other one.',
+                ],
+            ],
         ]);
-        return $queryType;
     }
 
     private static function getEpisodeType(): EntityObjectType
@@ -73,26 +72,24 @@ private static function getEpisodeType(): EntityObjectType
             'description' => 'A film in the Star Wars Trilogy',
             'fields' => [
                 'id' => [
-                    'type' => Type::nonNull(Type::int())
+                    'type' => Type::nonNull(Type::int()),
                 ],
                 'title' => [
-                    'type' => Type::nonNull(Type::string())
+                    'type' => Type::nonNull(Type::string()),
                 ],
                 'characters' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull(self::getCharacterType()))),
-                    'resolve' => function ($root) {
-                        return StarWarsData::getCharactersByIds($root['characters']);
-                    },
-                    'provides' => 'name'
-                ]
+                    'resolve' => static fn ($root): array => StarWarsData::getCharactersByIds($root['characters']),
+                    'provides' => 'name',
+                ],
             ],
             EntityObjectType::FIELD_KEY_FIELDS => ['id'],
-            EntityObjectType::FIELD_REFERENCE_RESOLVER => function ($ref) {
-                // print_r($ref);
+            EntityObjectType::FIELD_REFERENCE_RESOLVER => static function (array $ref): array {
                 $entity = StarWarsData::getEpisodeById($ref['id']);
-                $entity["__typename"] = "Episode";
+                $entity['__typename'] = 'Episode';
+
                 return $entity;
-            }
+            },
         ]);
     }
 
@@ -104,21 +101,19 @@ private static function getCharacterType(): EntityRefObjectType
             'fields' => [
                 'id' => [
                     'type' => Type::nonNull(Type::int()),
-                    'isExternal' => true
+                    'isExternal' => true,
                 ],
                 'name' => [
                     'type' => Type::nonNull(Type::string()),
-                    'isExternal' => true
+                    'isExternal' => true,
                 ],
                 'locations' => [
                     'type' => Type::nonNull(Type::listOf(self::getLocationType())),
-                    'resolve' => function ($root) {
-                        return StarWarsData::getLocationsByIds($root['locations']);
-                    },
-                    'requires' => 'name'
-                ]
+                    'resolve' => static fn ($root): array => StarWarsData::getLocationsByIds($root['locations']),
+                    'requires' => 'name',
+                ],
             ],
-            EntityObjectType::FIELD_KEY_FIELDS => ['id']
+            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
         ]);
     }
 
@@ -130,14 +125,14 @@ private static function getLocationType(): EntityRefObjectType
             'fields' => [
                 'id' => [
                     'type' => Type::nonNull(Type::int()),
-                    'isExternal' => true
+                    'isExternal' => true,
                 ],
                 'name' => [
                     'type' => Type::nonNull(Type::string()),
-                    'isExternal' => true
-                ]
+                    'isExternal' => true,
+                ],
             ],
-            EntityObjectType::FIELD_KEY_FIELDS => ['id']
+            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
         ]);
     }
 }

From e0c45d7528f688dcfc68095866b7db523b84f4c5 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 11:41:42 +0300
Subject: [PATCH 20/40] Fix method call params order

---
 test/DirectivesTest.php | 16 ++++++++--------
 test/EntitiesTest.php   | 18 +++++++++---------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/test/DirectivesTest.php b/test/DirectivesTest.php
index 7023c6f..a71aa04 100644
--- a/test/DirectivesTest.php
+++ b/test/DirectivesTest.php
@@ -23,8 +23,8 @@ public function testKeyDirective(): void
 
         $expectedLocations = [DirectiveLocation::OBJECT, DirectiveLocation::IFACE];
 
-        $this->assertEquals($config['name'], 'key');
-        $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
+        $this->assertEquals('key', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
     public function testExternalDirective(): void
@@ -33,8 +33,8 @@ public function testExternalDirective(): void
 
         $expectedLocations = [DirectiveLocation::FIELD_DEFINITION];
 
-        $this->assertEquals($config['name'], 'external');
-        $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
+        $this->assertEquals('external', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
     public function testRequiresDirective(): void
@@ -43,8 +43,8 @@ public function testRequiresDirective(): void
 
         $expectedLocations = [DirectiveLocation::FIELD_DEFINITION];
 
-        $this->assertEquals($config['name'], 'requires');
-        $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
+        $this->assertEquals('requires', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
     public function testProvidesDirective(): void
@@ -53,8 +53,8 @@ public function testProvidesDirective(): void
 
         $expectedLocations = [DirectiveLocation::FIELD_DEFINITION];
 
-        $this->assertEquals($config['name'], 'provides');
-        $this->assertEqualsCanonicalizing($config['locations'], $expectedLocations);
+        $this->assertEquals('provides', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
     public function testItAddsDirectivesToSchema(): void
diff --git a/test/EntitiesTest.php b/test/EntitiesTest.php
index e0e51ec..9c03f73 100644
--- a/test/EntitiesTest.php
+++ b/test/EntitiesTest.php
@@ -16,11 +16,11 @@ class EntitiesTest extends TestCase
 
     public function testCreatingEntityType(): void
     {
-        $userTypeKeyFields = ['id', 'email'];
+        $expectedKeyFields = ['id', 'email'];
 
         $userType = new EntityObjectType([
             'name' => 'User',
-            'keyFields' => $userTypeKeyFields,
+            'keyFields' => $expectedKeyFields,
             'fields' => [
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
@@ -29,17 +29,17 @@ public function testCreatingEntityType(): void
             ],
         ]);
 
-        $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
+        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
         $this->assertMatchesSnapshot($userType->config);
     }
 
     public function testCreatingEntityTypeWithCallable(): void
     {
-        $userTypeKeyFields = ['id', 'email'];
+        $expectedKeyFields = ['id', 'email'];
 
         $userType = new EntityObjectType([
             'name' => 'User',
-            'keyFields' => $userTypeKeyFields,
+            'keyFields' => $expectedKeyFields,
             'fields' => function () {
                 return [
                     'id' => ['type' => Type::int()],
@@ -50,7 +50,7 @@ public function testCreatingEntityTypeWithCallable(): void
             },
         ]);
 
-        $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
+        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
         $this->assertMatchesSnapshot($userType->config);
     }
 
@@ -85,18 +85,18 @@ public function testResolvingEntityReference(): void
 
     public function testCreatingEntityRefType(): void
     {
-        $userTypeKeyFields = ['id', 'email'];
+        $expectedKeyFields = ['id', 'email'];
 
         $userType = new EntityRefObjectType([
             'name' => 'User',
-            'keyFields' => $userTypeKeyFields,
+            'keyFields' => $expectedKeyFields,
             'fields' => [
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
             ],
         ]);
 
-        $this->assertEqualsCanonicalizing($userType->getKeyFields(), $userTypeKeyFields);
+        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
         $this->assertMatchesSnapshot($userType->config);
     }
 }

From 10a2a4ae410385431f5cc5042c96f528745e3b3d Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 12:58:53 +0300
Subject: [PATCH 21/40] Fix code style

---
 src/Types/EntityObjectType.php | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index 227e6bb..db3a72b 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -50,14 +50,16 @@ class EntityObjectType extends ObjectType
     public const FIELD_DIRECTIVE_PROVIDES = 'provides';
     public const FIELD_DIRECTIVE_REQUIRES = 'requires';
 
-    /** @var array */
-    private $keyFields;
-
     /** @var callable|null */
     public $referenceResolver = null;
 
     /**
-     * @param mixed[] $config
+     * @var array<int,string>|array<int|string,string|array<int|string,mixed>>
+     */
+    private array $keyFields;
+
+    /**
+     * @param array<string,mixed> $config
      */
     public function __construct(array $config)
     {
@@ -74,7 +76,7 @@ public function __construct(array $config)
     /**
      * Gets the fields that serve as the unique key or identifier of the entity.
      *
-     * @return array
+     * @return array<int,string>|array<int|string,string|array<int|string,mixed>>
      */
     public function getKeyFields(): array
     {
@@ -106,30 +108,23 @@ public function resolveReference($ref, $context = null, $info = null)
         return ($this->referenceResolver)($ref, $context, $info);
     }
 
-    /**
-     * @return void
-     */
-    private function validateReferenceResolver()
+    private function validateReferenceResolver(): void
     {
         Utils::invariant(isset($this->referenceResolver), 'No reference resolver was set in the configuration.');
     }
 
     /**
      * @param array{ __typename: mixed } $ref
-     *
-     * @return void
      */
-    private function validateReferenceKeys($ref)
+    private function validateReferenceKeys(array $ref): void
     {
         Utils::invariant(isset($ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
     }
 
     /**
      * @param array{ __resolveReference: mixed } $config
-     *
-     * @return void
      */
-    public static function validateResolveReference(array $config)
+    public static function validateResolveReference(array $config): void
     {
         Utils::invariant(\is_callable($config[self::FIELD_REFERENCE_RESOLVER]), 'Reference resolver has to be callable.');
     }

From b5d5e481f0445bdc0c05c6b1070f7a5ff189354d Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Wed, 3 Aug 2022 09:12:40 +0300
Subject: [PATCH 22/40] Sort schema printer methods

---
 src/Utils/FederatedSchemaPrinter.php | 86 ++++++++++++++--------------
 1 file changed, 43 insertions(+), 43 deletions(-)

diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index 035864d..ee4960d 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -100,28 +100,6 @@ public static function printType(Type $type, array $options = []): string
         return parent::printType($type, $options);
     }
 
-    /**
-     * @param array<string, bool> $options
-     */
-    protected static function printObject(ObjectType $type, array $options): string
-    {
-        if (empty($type->getFields())) {
-            return '';
-        }
-
-        $implementedInterfaces = static::printImplementedInterfaces($type);
-        $extends = FederatedSchema::isReservedRootType($type->name) ? 'extend ' : '';
-
-        return static::printDescription($options, $type) .
-            sprintf(
-                "%stype %s%s {\n%s\n}",
-                $extends,
-                $type->name,
-                $implementedInterfaces,
-                static::printFields($options, $type)
-            );
-    }
-
     /**
      * @param array<string, bool> $options
      */
@@ -142,6 +120,27 @@ protected static function printEntityObject(EntityObjectType $type, array $optio
             );
     }
 
+    protected static function printFieldFederatedDirectives(FieldDefinition $field): string
+    {
+        $directives = [];
+
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL])
+            && true === $field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL]
+        ) {
+            $directives[] = '@external';
+        }
+
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES])) {
+            $directives[] = sprintf('@provides(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]));
+        }
+
+        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES])) {
+            $directives[] = sprintf('@requires(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]));
+        }
+
+        return implode(' ', $directives);
+    }
+
     /**
      * @param array<string, bool> $options
      * @param EntityObjectType|InterfaceType|ObjectType|TypeWithFields $type
@@ -178,27 +177,6 @@ static function (FieldDefinition $f, $i) use ($options) {
         );
     }
 
-    protected static function printFieldFederatedDirectives(FieldDefinition $field): string
-    {
-        $directives = [];
-
-        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL])
-            && true === $field->config[EntityObjectType::FIELD_DIRECTIVE_IS_EXTERNAL]
-        ) {
-            $directives[] = '@external';
-        }
-
-        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES])) {
-            $directives[] = sprintf('@provides(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_PROVIDES]));
-        }
-
-        if (isset($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES])) {
-            $directives[] = sprintf('@requires(fields: "%s")', static::printKeyFields($field->config[EntityObjectType::FIELD_DIRECTIVE_REQUIRES]));
-        }
-
-        return implode(' ', $directives);
-    }
-
     protected static function printImplementedInterfaces(ObjectType $type): string
     {
         $interfaces = $type->getInterfaces();
@@ -240,4 +218,26 @@ protected static function printKeyFields($keyFields): string
 
         return implode(' ', $parts);
     }
+
+    /**
+     * @param array<string, bool> $options
+     */
+    protected static function printObject(ObjectType $type, array $options): string
+    {
+        if (empty($type->getFields())) {
+            return '';
+        }
+
+        $implementedInterfaces = static::printImplementedInterfaces($type);
+        $extends = FederatedSchema::isReservedRootType($type->name) ? 'extend ' : '';
+
+        return static::printDescription($options, $type) .
+            sprintf(
+                "%stype %s%s {\n%s\n}",
+                $extends,
+                $type->name,
+                $implementedInterfaces,
+                static::printFields($options, $type)
+            );
+    }
 }

From 17bf125b15c072ee50ee48923990690a4b57b97d Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 10:52:06 +0300
Subject: [PATCH 23/40] Add directives of Apollo Federation v2

---
 src/Directives.php                            | 55 +++++++++++++++++--
 src/Directives/ExternalDirective.php          |  2 +
 src/Directives/InaccessibleDirective.php      | 31 +++++++++++
 src/Directives/OverrideDirective.php          | 34 ++++++++++++
 src/Directives/ProvidesDirective.php          |  2 +
 src/Directives/RequiresDirective.php          |  2 +
 src/Directives/ShareableDirective.php         | 26 +++++++++
 src/Enum/DirectiveEnum.php                    | 16 +++++-
 test/DirectivesTest.php                       | 25 +++++++++
 ...sTest__testItAddsDirectivesToSchema__1.txt |  8 ++-
 .../SchemaTest__testSchemaSdl__1.txt          |  8 ++-
 11 files changed, 201 insertions(+), 8 deletions(-)
 create mode 100644 src/Directives/InaccessibleDirective.php
 create mode 100644 src/Directives/OverrideDirective.php
 create mode 100644 src/Directives/ShareableDirective.php

diff --git a/src/Directives.php b/src/Directives.php
index ec21a05..29d8de2 100644
--- a/src/Directives.php
+++ b/src/Directives.php
@@ -5,19 +5,31 @@
 namespace Apollo\Federation;
 
 use Apollo\Federation\Directives\ExternalDirective;
+use Apollo\Federation\Directives\InaccessibleDirective;
 use Apollo\Federation\Directives\KeyDirective;
+use Apollo\Federation\Directives\OverrideDirective;
 use Apollo\Federation\Directives\ProvidesDirective;
 use Apollo\Federation\Directives\RequiresDirective;
+use Apollo\Federation\Directives\ShareableDirective;
 use Apollo\Federation\Enum\DirectiveEnum;
-use GraphQL\Type\Definition\Directive;
 
 /**
  * Helper class to get directives for annotating federated entity types.
  */
 class Directives
 {
-    /** @var array<string,Directive> */
-    private static $directives = null;
+    /**
+     * @var array{
+     *     external: ExternalDirective,
+     *     inaccessible: InaccessibleDirective,
+     *     key: KeyDirective,
+     *     override: OverrideDirective,
+     *     requires: RequiresDirective,
+     *     provides: ProvidesDirective,
+     *     shareable: ShareableDirective,
+     * }|null
+     */
+    private static ?array $directives = null;
 
     /**
      * Gets the @key directive.
@@ -35,6 +47,22 @@ public static function external(): ExternalDirective
         return self::getDirectives()[DirectiveEnum::EXTERNAL];
     }
 
+    /**
+     * Gets the @inaccessible directive.
+     */
+    public static function inaccessible(): InaccessibleDirective
+    {
+        return self::getDirectives()[DirectiveEnum::INACCESSIBLE];
+    }
+
+    /**
+     * Gets the @override directive.
+     */
+    public static function override(): OverrideDirective
+    {
+        return self::getDirectives()[DirectiveEnum::OVERRIDE];
+    }
+
     /**
      * Gets the @requires directive.
      */
@@ -51,19 +79,38 @@ public static function provides(): ProvidesDirective
         return self::getDirectives()[DirectiveEnum::PROVIDES];
     }
 
+    /**
+     * Gets the @shareable directive.
+     */
+    public static function shareable(): ShareableDirective
+    {
+        return self::getDirectives()[DirectiveEnum::SHAREABLE];
+    }
+
     /**
      * Gets the directives that can be used on federated entity types.
      *
-     * @return array<string,Directive>
+     * @return array{
+     *     external: ExternalDirective,
+     *     inaccessible: InaccessibleDirective,
+     *     key: KeyDirective,
+     *     override: OverrideDirective,
+     *     requires: RequiresDirective,
+     *     provides: ProvidesDirective,
+     *     shareable: ShareableDirective,
+     * }
      */
     public static function getDirectives(): array
     {
         if (!self::$directives) {
             self::$directives = [
                 DirectiveEnum::EXTERNAL => new ExternalDirective(),
+                DirectiveEnum::INACCESSIBLE => new InaccessibleDirective(),
                 DirectiveEnum::KEY => new KeyDirective(),
+                DirectiveEnum::OVERRIDE => new OverrideDirective(),
                 DirectiveEnum::REQUIRES => new RequiresDirective(),
                 DirectiveEnum::PROVIDES => new ProvidesDirective(),
+                DirectiveEnum::SHAREABLE => new ShareableDirective(),
             ];
         }
 
diff --git a/src/Directives/ExternalDirective.php b/src/Directives/ExternalDirective.php
index 3c8d024..4b15f6a 100644
--- a/src/Directives/ExternalDirective.php
+++ b/src/Directives/ExternalDirective.php
@@ -10,6 +10,8 @@
  * The `@external` directive is used to mark a field as owned by another service. This
  * allows service A to use fields from service B while also knowing at runtime the
  * types of that field.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#external
  */
 class ExternalDirective extends Directive
 {
diff --git a/src/Directives/InaccessibleDirective.php b/src/Directives/InaccessibleDirective.php
new file mode 100644
index 0000000..aa43dbc
--- /dev/null
+++ b/src/Directives/InaccessibleDirective.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Directives;
+
+use Apollo\Federation\Enum\DirectiveEnum;
+use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Directive;
+
+/**
+ * The `@inaccessible` directive indicates that a field or type should be omitted from the gateway's API schema,
+ * even if it's also defined in other subgraphs.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#inaccessible
+ */
+class InaccessibleDirective extends Directive
+{
+    public function __construct()
+    {
+        parent::__construct([
+            'name' => DirectiveEnum::INACCESSIBLE,
+            'locations' => [
+                DirectiveLocation::FIELD_DEFINITION,
+                DirectiveLocation::IFACE,
+                DirectiveLocation::OBJECT,
+                DirectiveLocation::UNION,
+            ],
+        ]);
+    }
+}
diff --git a/src/Directives/OverrideDirective.php b/src/Directives/OverrideDirective.php
new file mode 100644
index 0000000..61e62e3
--- /dev/null
+++ b/src/Directives/OverrideDirective.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Directives;
+
+use Apollo\Federation\Enum\DirectiveEnum;
+use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Directive;
+use GraphQL\Type\Definition\FieldArgument;
+use GraphQL\Type\Definition\Type;
+
+/**
+ * The `@override` directive indicates that a field is now resolved by this subgraph
+ * instead of another subgraph where it's also defined.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#override
+ */
+class OverrideDirective extends Directive
+{
+    public function __construct()
+    {
+        parent::__construct([
+            'name' => DirectiveEnum::OVERRIDE,
+            'locations' => [DirectiveLocation::FIELD_DEFINITION],
+            'args' => [
+                new FieldArgument([
+                    'name' => 'from',
+                    'type' => Type::nonNull(Type::string()),
+                ]),
+            ],
+        ]);
+    }
+}
diff --git a/src/Directives/ProvidesDirective.php b/src/Directives/ProvidesDirective.php
index 24d9be1..63d70c3 100644
--- a/src/Directives/ProvidesDirective.php
+++ b/src/Directives/ProvidesDirective.php
@@ -11,6 +11,8 @@
 /**
  * The `@provides` directive is used to annotate the expected returned fieldset from a field
  * on a base type that is guaranteed to be selectable by the gateway.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#provides
  */
 class ProvidesDirective extends Directive
 {
diff --git a/src/Directives/RequiresDirective.php b/src/Directives/RequiresDirective.php
index d33bec3..42853ad 100644
--- a/src/Directives/RequiresDirective.php
+++ b/src/Directives/RequiresDirective.php
@@ -12,6 +12,8 @@
  * The `@requires` directive is used to annotate the required input fieldset from a base type
  * for a resolver. It is used to develop a query plan where the required fields may not be
  * needed by the client, but the service may need additional information from other services.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#requires
  */
 class RequiresDirective extends Directive
 {
diff --git a/src/Directives/ShareableDirective.php b/src/Directives/ShareableDirective.php
new file mode 100644
index 0000000..fd0d524
--- /dev/null
+++ b/src/Directives/ShareableDirective.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Directives;
+
+use Apollo\Federation\Enum\DirectiveEnum;
+use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\Directive;
+
+/**
+ * The `@shareable` directive indicates that an object type's field is allowed to be resolved
+ * by multiple subgraphs (by default, each field can be resolved by only one subgraph).
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#shareable
+ */
+class ShareableDirective extends Directive
+{
+    public function __construct()
+    {
+        parent::__construct([
+            'name' => DirectiveEnum::SHAREABLE,
+            'locations' => [DirectiveLocation::FIELD_DEFINITION, DirectiveLocation::OBJECT],
+        ]);
+    }
+}
diff --git a/src/Enum/DirectiveEnum.php b/src/Enum/DirectiveEnum.php
index 97ef22b..a0c039b 100644
--- a/src/Enum/DirectiveEnum.php
+++ b/src/Enum/DirectiveEnum.php
@@ -7,19 +7,31 @@
 class DirectiveEnum
 {
     public const EXTERNAL = 'external';
+    public const INACCESSIBLE = 'inaccessible';
     public const KEY = 'key';
+    public const OVERRIDE = 'override';
     public const PROVIDES = 'provides';
     public const REQUIRES = 'requires';
+    public const SHAREABLE = 'shareable';
+
+    /**
+     * @var string[]|null
+     */
+    protected static ?array $constants = null;
 
     /**
      * @return string[]
      */
     public static function getAll(): array
     {
-        return [self::EXTERNAL, self::KEY, self::PROVIDES, self::REQUIRES];
+        if (null === static::$constants) {
+            static::$constants = (new \ReflectionClass(static::class))->getConstants();
+        }
+
+        return static::$constants;
     }
 
-    private function __construct()
+    protected function __construct()
     {
         // forbid creation of an object
     }
diff --git a/test/DirectivesTest.php b/test/DirectivesTest.php
index a71aa04..6b3137a 100644
--- a/test/DirectivesTest.php
+++ b/test/DirectivesTest.php
@@ -37,6 +37,21 @@ public function testExternalDirective(): void
         $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
+    public function testInaccessibleDirective(): void
+    {
+        $config = Directives::inaccessible()->config;
+
+        $expectedLocations = [
+            DirectiveLocation::FIELD_DEFINITION,
+            DirectiveLocation::IFACE,
+            DirectiveLocation::OBJECT,
+            DirectiveLocation::UNION,
+        ];
+
+        $this->assertEquals('inaccessible', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
+    }
+
     public function testRequiresDirective(): void
     {
         $config = Directives::requires()->config;
@@ -57,6 +72,16 @@ public function testProvidesDirective(): void
         $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
+    public function testShareableDirective(): void
+    {
+        $config = Directives::shareable()->config;
+
+        $expectedLocations = [DirectiveLocation::FIELD_DEFINITION, DirectiveLocation::OBJECT];
+
+        $this->assertEquals('shareable', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
+    }
+
     public function testItAddsDirectivesToSchema(): void
     {
         $schema = new Schema([
diff --git a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
index fe9e678..b682900 100644
--- a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
+++ b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
@@ -1,11 +1,17 @@
+directive @external on FIELD_DEFINITION
+
+directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
+
 directive @key(fields: String!) on OBJECT | INTERFACE
 
-directive @external on FIELD_DEFINITION
+directive @override(from: String!) on FIELD_DEFINITION
 
 directive @requires(fields: String!) on FIELD_DEFINITION
 
 directive @provides(fields: String!) on FIELD_DEFINITION
 
+directive @shareable on FIELD_DEFINITION | OBJECT
+
 type Query {
   _: String
 }
diff --git a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
index fd4a936..a3767ed 100644
--- a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
+++ b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
@@ -1,11 +1,17 @@
+directive @external on FIELD_DEFINITION
+
+directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
+
 directive @key(fields: String!) on OBJECT | INTERFACE
 
-directive @external on FIELD_DEFINITION
+directive @override(from: String!) on FIELD_DEFINITION
 
 directive @requires(fields: String!) on FIELD_DEFINITION
 
 directive @provides(fields: String!) on FIELD_DEFINITION
 
+directive @shareable on FIELD_DEFINITION | OBJECT
+
 """A character in the Star Wars Trilogy"""
 type Character {
   id: Int!

From c0f39411de8aa66d87ae1cc54923f9c460da783c Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Thu, 4 Aug 2022 14:42:36 +0300
Subject: [PATCH 24/40] Implement directive @link

---
 src/Directives.php                            | 12 +++
 src/Directives/LinkDirective.php              | 78 +++++++++++++++
 src/Enum/DirectiveEnum.php                    |  1 +
 src/FederatedSchema.php                       |  1 +
 src/FederatedSchemaTrait.php                  | 94 ++++++++++++++-----
 src/Types/SchemaExtensionType.php             | 23 +++++
 src/Utils/FederatedSchemaPrinter.php          | 61 +++++++++++-
 test/DirectivesTest.php                       | 13 ++-
 ...sTest__testItAddsDirectivesToSchema__1.txt |  4 +
 .../SchemaTest__testSchemaSdl__1.txt          |  4 +
 .../SchemaTest__testServiceSdl__1.yml         |  2 +-
 11 files changed, 264 insertions(+), 29 deletions(-)
 create mode 100644 src/Directives/LinkDirective.php
 create mode 100644 src/Types/SchemaExtensionType.php

diff --git a/src/Directives.php b/src/Directives.php
index 29d8de2..08a1b19 100644
--- a/src/Directives.php
+++ b/src/Directives.php
@@ -7,6 +7,7 @@
 use Apollo\Federation\Directives\ExternalDirective;
 use Apollo\Federation\Directives\InaccessibleDirective;
 use Apollo\Federation\Directives\KeyDirective;
+use Apollo\Federation\Directives\LinkDirective;
 use Apollo\Federation\Directives\OverrideDirective;
 use Apollo\Federation\Directives\ProvidesDirective;
 use Apollo\Federation\Directives\RequiresDirective;
@@ -23,6 +24,7 @@ class Directives
      *     external: ExternalDirective,
      *     inaccessible: InaccessibleDirective,
      *     key: KeyDirective,
+     *     link: LinkDirective,
      *     override: OverrideDirective,
      *     requires: RequiresDirective,
      *     provides: ProvidesDirective,
@@ -55,6 +57,14 @@ public static function inaccessible(): InaccessibleDirective
         return self::getDirectives()[DirectiveEnum::INACCESSIBLE];
     }
 
+    /**
+     * Gets the `link` directive.
+     */
+    public static function link(): LinkDirective
+    {
+        return self::getDirectives()[DirectiveEnum::LINK];
+    }
+
     /**
      * Gets the @override directive.
      */
@@ -94,6 +104,7 @@ public static function shareable(): ShareableDirective
      *     external: ExternalDirective,
      *     inaccessible: InaccessibleDirective,
      *     key: KeyDirective,
+     *     link: LinkDirective,
      *     override: OverrideDirective,
      *     requires: RequiresDirective,
      *     provides: ProvidesDirective,
@@ -107,6 +118,7 @@ public static function getDirectives(): array
                 DirectiveEnum::EXTERNAL => new ExternalDirective(),
                 DirectiveEnum::INACCESSIBLE => new InaccessibleDirective(),
                 DirectiveEnum::KEY => new KeyDirective(),
+                DirectiveEnum::LINK => new LinkDirective(),
                 DirectiveEnum::OVERRIDE => new OverrideDirective(),
                 DirectiveEnum::REQUIRES => new RequiresDirective(),
                 DirectiveEnum::PROVIDES => new ProvidesDirective(),
diff --git a/src/Directives/LinkDirective.php b/src/Directives/LinkDirective.php
new file mode 100644
index 0000000..87f3c27
--- /dev/null
+++ b/src/Directives/LinkDirective.php
@@ -0,0 +1,78 @@
+<?php
+
+namespace Apollo\Federation\Directives;
+
+use Apollo\Federation\Enum\DirectiveEnum;
+use GraphQL\Error\InvariantViolation;
+use GraphQL\Language\DirectiveLocation;
+use GraphQL\Type\Definition\CustomScalarType;
+use GraphQL\Type\Definition\Directive;
+use GraphQL\Type\Definition\FieldArgument;
+use GraphQL\Type\Definition\Type;
+
+/**
+ * The `@link` directive is used to ...
+ *
+ * @see https://specs.apollo.dev/link/v1.0/
+ */
+class LinkDirective extends Directive
+{
+    public function __construct()
+    {
+        $linkImport = new CustomScalarType([
+            'name' => 'link_Import',
+            'serialize' => static fn ($value) => json_encode($value, \JSON_THROW_ON_ERROR),
+            'parseValue' => static function ($value) {
+                if (\is_string($value)) {
+                    return $value;
+                }
+
+                if (!\is_array($value)) {
+                    throw new InvariantViolation('"link_Import" must be a string or an array');
+                }
+                $permittedKeys = ['name', 'as'];
+                $keys = array_keys($value);
+                if ($permittedKeys !== array_intersect($permittedKeys, $keys) || array_diff($keys, $permittedKeys)) {
+                    throw new InvariantViolation('"link_Import" must contain only keys "name" and "as" and they are required');
+                }
+
+                if (2 !== \count(array_filter($value))) {
+                    throw new InvariantViolation('The "name" and "as" part of "link_Import" be not empty');
+                }
+
+                $prefixes = array_unique([$value['name'][0], $value['as'][0]]);
+                if (\in_array('@', $prefixes, true) && 2 !== \count($prefixes)) {
+                    // https://specs.apollo.dev/link/v1.0/#Import
+                    throw new InvariantViolation('The "name" and "as" part of "link_Import" be of the same type');
+                }
+
+                return $value;
+            },
+        ]);
+
+        parent::__construct([
+            'name' => DirectiveEnum::LINK,
+            'locations' => [DirectiveLocation::SCHEMA],
+            'args' => [
+                new FieldArgument([
+                    'name' => 'url',
+                    'type' => Type::nonNull(Type::string()),
+                ]),
+                new FieldArgument([
+                    'name' => 'as',
+                    'type' => Type::string(),
+                ]),
+                new FieldArgument([
+                    'name' => 'for',
+                    // TODO use union type (enum & string) and declare required enum
+                    'type' => Type::string(),
+                ]),
+                new FieldArgument([
+                    'name' => 'import',
+                    'type' => Type::listOf(Type::nonNull($linkImport)),
+                ]),
+            ],
+            'isRepeatable' => true,
+        ]);
+    }
+}
diff --git a/src/Enum/DirectiveEnum.php b/src/Enum/DirectiveEnum.php
index a0c039b..06abf9a 100644
--- a/src/Enum/DirectiveEnum.php
+++ b/src/Enum/DirectiveEnum.php
@@ -9,6 +9,7 @@ class DirectiveEnum
     public const EXTERNAL = 'external';
     public const INACCESSIBLE = 'inaccessible';
     public const KEY = 'key';
+    public const LINK = 'link';
     public const OVERRIDE = 'override';
     public const PROVIDES = 'provides';
     public const REQUIRES = 'requires';
diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index f3b3fd4..8ce2c7c 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -82,6 +82,7 @@ public function __construct(array $config)
     {
         $this->entityTypes = $this->extractEntityTypes($config);
         $this->entityDirectives = Directives::getDirectives();
+        $this->schemaExtensionTypes = $this->extractSchemaExtensionTypes($config);
 
         $config = array_merge($config, $this->getEntityDirectivesConfig($config), $this->getQueryTypeConfig($config));
 
diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index 5afbffe..6942362 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -5,6 +5,7 @@
 namespace Apollo\Federation;
 
 use Apollo\Federation\Types\EntityObjectType;
+use Apollo\Federation\Types\SchemaExtensionType;
 use Apollo\Federation\Utils\FederatedSchemaPrinter;
 use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\Directive;
@@ -22,6 +23,11 @@ trait FederatedSchemaTrait
      */
     protected array $entityTypes = [];
 
+    /**
+     * @var SchemaExtensionType[]
+     */
+    protected array $schemaExtensionTypes = [];
+
     /**
      * @var Directive[]
      */
@@ -42,7 +48,15 @@ public function getEntityTypes(): array
      */
     public function hasEntityTypes(): bool
     {
-        return !empty($this->getEntityTypes());
+        return !empty($this->entityTypes);
+    }
+
+    /**
+     * @return SchemaExtensionType[]
+     */
+    public function getSchemaExtensionTypes(): array
+    {
+        return $this->schemaExtensionTypes;
     }
 
     /**
@@ -59,22 +73,25 @@ protected function getEntityDirectivesConfig(array $config): array
     }
 
     /**
-     * @param array<string,mixed> $config
+     * @param array{ query: ObjectType } $config
      *
      * @return array{ query: ObjectType }
      */
     protected function getQueryTypeConfig(array $config): array
     {
         $queryTypeConfig = $config['query']->config;
-        if (\is_callable($queryTypeConfig['fields'])) {
-            $queryTypeConfig['fields'] = $queryTypeConfig['fields']();
-        }
+        $fields = $queryTypeConfig['fields'];
+        $queryTypeConfig['fields'] = function () use ($config, $fields) {
+            if (\is_callable($fields)) {
+                $fields = $fields();
+            }
 
-        $queryTypeConfig['fields'] = array_merge(
-            $queryTypeConfig['fields'],
-            $this->getQueryTypeServiceFieldConfig(),
-            $this->getQueryTypeEntitiesFieldConfig($config)
-        );
+            return array_merge(
+                $fields,
+                $this->getQueryTypeServiceFieldConfig(),
+                $this->getQueryTypeEntitiesFieldConfig($config)
+            );
+        };
 
         return [
             'query' => new ObjectType($queryTypeConfig),
@@ -87,9 +104,9 @@ protected function getQueryTypeConfig(array $config): array
     protected function getQueryTypeServiceFieldConfig(): array
     {
         $serviceType = new ObjectType([
-            'name' => self::RESERVED_TYPE_SERVICE,
+            'name' => FederatedSchema::RESERVED_TYPE_SERVICE,
             'fields' => [
-                self::RESERVED_FIELD_SDL => [
+                FederatedSchema::RESERVED_FIELD_SDL => [
                     'type' => Type::string(),
                     'resolve' => fn (): string => FederatedSchemaPrinter::doPrint($this),
                 ],
@@ -97,7 +114,7 @@ protected function getQueryTypeServiceFieldConfig(): array
         ]);
 
         return [
-            self::RESERVED_FIELD_SERVICE => [
+            FederatedSchema::RESERVED_FIELD_SERVICE => [
                 'type' => Type::nonNull($serviceType),
                 'resolve' => static fn (): array => [],
             ],
@@ -111,25 +128,25 @@ protected function getQueryTypeServiceFieldConfig(): array
      */
     protected function getQueryTypeEntitiesFieldConfig(?array $config): array
     {
-        if (!$this->hasEntityTypes()) {
+        if (!$this->entityTypes) {
             return [];
         }
 
         $entityType = new UnionType([
-            'name' => self::RESERVED_TYPE_ENTITY,
+            'name' => FederatedSchema::RESERVED_TYPE_ENTITY,
             'types' => array_values($this->getEntityTypes()),
         ]);
 
         $anyType = new CustomScalarType([
-            'name' => self::RESERVED_TYPE_ANY,
+            'name' => FederatedSchema::RESERVED_TYPE_ANY,
             'serialize' => static fn ($value) => $value,
         ]);
 
         return [
-            self::RESERVED_FIELD_ENTITIES => [
+            FederatedSchema::RESERVED_FIELD_ENTITIES => [
                 'type' => Type::listOf($entityType),
                 'args' => [
-                    self::RESERVED_FIELD_REPRESENTATIONS => [
+                    FederatedSchema::RESERVED_FIELD_REPRESENTATIONS => [
                         'type' => Type::nonNull(Type::listOf(Type::nonNull($anyType))),
                     ],
                 ],
@@ -147,25 +164,24 @@ protected function getQueryTypeEntitiesFieldConfig(?array $config): array
     protected function resolve($root, $args, $context, $info): array
     {
         return array_map(static function ($ref) use ($context, $info) {
-            Utils::invariant(isset($ref[self::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
+            Utils::invariant(isset($ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
 
-            $typeName = $ref[self::RESERVED_FIELD_TYPE_NAME];
+            $typeName = $ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME];
             $type = $info->schema->getType($typeName);
 
             Utils::invariant(
-                $type && $type instanceof EntityObjectType,
-                sprintf(
-                    'The _entities resolver tried to load an entity for type "%s", but no object type of that name was found in the schema',
-                    $type->name
-                )
+                $type instanceof EntityObjectType,
+                'The _entities resolver tried to load an entity for type "%s", but no object type of that name was found in the schema',
+                $type->name
             );
 
+            /** @var EntityObjectType $type */
             if (!$type->hasReferenceResolver()) {
                 return $ref;
             }
 
             return $type->resolveReference($ref, $context, $info);
-        }, $args[self::RESERVED_FIELD_REPRESENTATIONS]);
+        }, $args[FederatedSchema::RESERVED_FIELD_REPRESENTATIONS]);
     }
 
     /**
@@ -186,4 +202,30 @@ protected function extractEntityTypes(array $config): array
 
         return $entityTypes;
     }
+
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return SchemaExtensionType[]
+     */
+    protected function extractSchemaExtensionTypes(array $config): array
+    {
+        $typeMap = [];
+        $configTypes = $config['types'] ?? [];
+        if (\is_array($configTypes)) {
+            $typeMap = $configTypes;
+        } elseif (\is_callable($configTypes)) {
+            $typeMap = $configTypes();
+        }
+
+        $types = [];
+
+        foreach ($typeMap as $type) {
+            if ($type instanceof SchemaExtensionType) {
+                $types[$type->name] = $type;
+            }
+        }
+
+        return $types;
+    }
 }
diff --git a/src/Types/SchemaExtensionType.php b/src/Types/SchemaExtensionType.php
new file mode 100644
index 0000000..b19843a
--- /dev/null
+++ b/src/Types/SchemaExtensionType.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Types;
+
+use GraphQL\Type\Definition\CompositeType;
+use GraphQL\Type\Definition\NamedType;
+use GraphQL\Type\Definition\OutputType;
+use GraphQL\Type\Definition\Type;
+
+class SchemaExtensionType extends Type implements OutputType, CompositeType, NamedType
+{
+    public const FIELD_KEY_LINKS = 'links';
+
+    /**
+     * @param array<string,mixed> $config
+     */
+    public function __construct(array $config)
+    {
+        $this->config = $config;
+    }
+}
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index ee4960d..a90d94a 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -35,6 +35,7 @@
 use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
+use Apollo\Federation\Types\SchemaExtensionType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldDefinition;
 use GraphQL\Type\Definition\InterfaceType;
@@ -93,7 +94,8 @@ public static function printType(Type $type, array $options = []): string
 
         if (($type instanceof ScalarType && FederatedSchema::RESERVED_TYPE_ANY === $type->name)
             || ($type instanceof ObjectType && FederatedSchema::RESERVED_TYPE_SERVICE === $type->name)
-            || ($type instanceof UnionType && FederatedSchema::RESERVED_TYPE_ENTITY === $type->name)) {
+            || ($type instanceof UnionType && FederatedSchema::RESERVED_TYPE_ENTITY === $type->name)
+            || ($type instanceof SchemaExtensionType)) {
             return '';
         }
 
@@ -219,6 +221,40 @@ protected static function printKeyFields($keyFields): string
         return implode(' ', $parts);
     }
 
+    /**
+     * @param array<string,mixed> $linkConfig
+     */
+    protected static function printLinkDirectiveConfig(array $linkConfig): string
+    {
+        $arguments = [];
+        foreach ($linkConfig as $name => $value) {
+            if (null === $value) {
+                continue;
+            }
+            $arguments[] = sprintf('%s: %s', $name, static::printLinkDirectiveArgumentValue($value, $name));
+        }
+
+        return sprintf('@link(%s)', implode(', ', $arguments));
+    }
+
+    /**
+     * @param string|array<int,string|array<string,string>> $argument
+     */
+    protected static function printLinkDirectiveArgumentValue($argument, string $name): string
+    {
+        if (\is_string($argument)) {
+            return '"' . $argument . '"';
+        }
+        if ('import' !== $name) {
+            throw new \InvalidArgumentException(sprintf('Value of %s must be a string', $name));
+        }
+        if (!\is_array($argument)) {
+            throw new \InvalidArgumentException('Invalid type of "import" argument value');
+        }
+
+        return json_encode($argument, \JSON_THROW_ON_ERROR);
+    }
+
     /**
      * @param array<string, bool> $options
      */
@@ -240,4 +276,27 @@ protected static function printObject(ObjectType $type, array $options): string
                 static::printFields($options, $type)
             );
     }
+
+    /**
+     * @param FederatedSchema $schema
+     */
+    protected static function printSchemaDefinition(Schema $schema): string
+    {
+        $parts = [parent::printSchemaDefinition($schema)];
+        foreach ($schema->getSchemaExtensionTypes() as $schemaExtensionType) {
+            $parts[] = self::printSchemaExtensionType($schemaExtensionType);
+        }
+
+        return implode("\n\n", array_filter($parts));
+    }
+
+    protected static function printSchemaExtensionType(SchemaExtensionType $schemaExtensionType): string
+    {
+        $links = $schemaExtensionType->config[SchemaExtensionType::FIELD_KEY_LINKS] ?? [];
+
+        return sprintf(
+            'extend schema %s\n',
+            implode("\n", array_map(static fn (array $x): string => static::printLinkDirectiveConfig($x), $links)),
+        );
+    }
 }
diff --git a/test/DirectivesTest.php b/test/DirectivesTest.php
index 6b3137a..fe51d53 100644
--- a/test/DirectivesTest.php
+++ b/test/DirectivesTest.php
@@ -13,7 +13,7 @@
 use PHPUnit\Framework\TestCase;
 use Spatie\Snapshots\MatchesSnapshots;
 
-class DirectivesTest extends TestCase
+final class DirectivesTest extends TestCase
 {
     use MatchesSnapshots;
 
@@ -52,6 +52,17 @@ public function testInaccessibleDirective(): void
         $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
     }
 
+    public function testLinkDirective(): void
+    {
+        $config = Directives::link()->config;
+
+        $expectedLocations = [DirectiveLocation::SCHEMA];
+
+        $this->assertEquals('link', $config['name']);
+        $this->assertEqualsCanonicalizing($expectedLocations, $config['locations']);
+        $this->assertTrue($config['isRepeatable']);
+    }
+
     public function testRequiresDirective(): void
     {
         $config = Directives::requires()->config;
diff --git a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
index b682900..6f55ba2 100644
--- a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
+++ b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
@@ -4,6 +4,8 @@ directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
 
 directive @key(fields: String!) on OBJECT | INTERFACE
 
+directive @link(url: String!, as: String, for: String, import: [link_Import!]) repeatable on SCHEMA
+
 directive @override(from: String!) on FIELD_DEFINITION
 
 directive @requires(fields: String!) on FIELD_DEFINITION
@@ -15,3 +17,5 @@ directive @shareable on FIELD_DEFINITION | OBJECT
 type Query {
   _: String
 }
+
+scalar link_Import
diff --git a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
index a3767ed..7718755 100644
--- a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
+++ b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
@@ -4,6 +4,8 @@ directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
 
 directive @key(fields: String!) on OBJECT | INTERFACE
 
+directive @link(url: String!, as: String, for: String, import: [link_Import!]) repeatable on SCHEMA
+
 directive @override(from: String!) on FIELD_DEFINITION
 
 directive @requires(fields: String!) on FIELD_DEFINITION
@@ -46,3 +48,5 @@ union _Entity = Episode | Character | Location
 type _Service {
   sdl: String
 }
+
+scalar link_Import
diff --git a/test/__snapshots__/SchemaTest__testServiceSdl__1.yml b/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
index 2cf44a2..799ec1c 100644
--- a/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
+++ b/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
@@ -1,2 +1,2 @@
 data:
-    _service: { sdl: "\"\"\"A character in the Star Wars Trilogy\"\"\"\nextend type Character @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n  locations: [Location]! @requires(fields: \"name\")\n}\n\n\"\"\"A film in the Star Wars Trilogy\"\"\"\ntype Episode @key(fields: \"id\") {\n  id: Int! \n  title: String! \n  characters: [Character!]! @provides(fields: \"name\")\n}\n\n\"\"\"A location in the Star Wars Trilogy\"\"\"\nextend type Location @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n}\n\nextend type Query {\n  episodes: [Episode!]! \n  deprecatedEpisodes: [Episode!]! @deprecated(reason: \"Because you should use the other one.\") \n}\n" }
+    _service: { sdl: "\"\"\"A character in the Star Wars Trilogy\"\"\"\nextend type Character @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n  locations: [Location]! @requires(fields: \"name\")\n}\n\n\"\"\"A film in the Star Wars Trilogy\"\"\"\ntype Episode @key(fields: \"id\") {\n  id: Int! \n  title: String! \n  characters: [Character!]! @provides(fields: \"name\")\n}\n\n\"\"\"A location in the Star Wars Trilogy\"\"\"\nextend type Location @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n}\n\nextend type Query {\n  episodes: [Episode!]! \n  deprecatedEpisodes: [Episode!]! @deprecated(reason: \"Because you should use the other one.\") \n}\n\nscalar link_Import\n" }

From 1bac625d985ecaf8b4857c94fd148c5864c98256 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Thu, 4 Aug 2022 15:21:03 +0300
Subject: [PATCH 25/40] Add handling of argument "resolvable" of directive @key

---
 README.md                                     | 12 ++----
 src/Directives/KeyDirective.php               | 11 +++++-
 src/FederatedSchema.php                       |  2 +-
 src/Types/EntityObjectType.php                | 39 +++++++++++++++----
 src/Utils/FederatedSchemaPrinter.php          |  9 ++++-
 test/EntitiesTest.php                         | 20 +++++-----
 test/StarWarsSchema.php                       |  6 +--
 ...sTest__testItAddsDirectivesToSchema__1.txt |  2 +-
 ...tiesTest__testCreatingEntityRefType__1.yml |  5 +--
 ..._testCreatingEntityTypeWithCallable__1.yml |  6 +--
 ...ntitiesTest__testCreatingEntityType__1.yml |  6 +--
 .../SchemaTest__testSchemaSdl__1.txt          |  2 +-
 12 files changed, 77 insertions(+), 43 deletions(-)

diff --git a/README.md b/README.md
index 589c85c..f03f5db 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ use GraphQL\Type\Definition\Type;
 
 $userType = new EntityObjectType([
     'name' => 'User',
-    'keyFields' => ['id', 'email'],
+    'keys' => [['fields' => 'id'], ['fields' => 'email']],
     'fields' => [
         'id' => ['type' => Type::int()],
         'email' => ['type' => Type::string()],
@@ -35,7 +35,7 @@ $userType = new EntityObjectType([
 ]);
 ```
 
-* `keyFields` — defines the entity's primary key, which consists of one or more of the fields. An entity's key cannot include fields that return a union or interface.
+* `keys` — defines the entity's primary key, which consists of one or more of the fields. An entity's key cannot include fields that return a union or interface.
 
 * `__resolveReference` — resolves the representation of the entity from the provided reference. Subgraphs use representations to reference entities from other subgraphs. A representation requires only an explicit __typename definition and values for the entity's primary key fields.
 
@@ -50,7 +50,7 @@ use Apollo\Federation\Types\EntityRefObjectType;
 
 $userType = new EntityRefObjectType([
     'name' => 'User',
-    'keyFields' => ['id', 'email'],
+    'keys' => [['fields' => 'id'], ['fields' => 'email']],
     'fields' => [
         'id' => ['type' => Type::int()],
         'email' => ['type' => Type::string()]
@@ -69,16 +69,12 @@ use Apollo\Federation\Types\EntityRefObjectType;
 
 $userType = new EntityRefObjectType([
     'name' => 'User',
-    'keyFields' => ['id', 'email'],
+    'keys' => [['fields' => 'id', 'resolvable' => false]],
     'fields' => [
         'id' => [
             'type' => Type::int(),
             'isExternal' => true
         ],
-        'email' => [
-            'type' => Type::string(),
-            'isExternal' => true
-        ]
     ]
 ]);
 ```
diff --git a/src/Directives/KeyDirective.php b/src/Directives/KeyDirective.php
index 4129547..c74f814 100644
--- a/src/Directives/KeyDirective.php
+++ b/src/Directives/KeyDirective.php
@@ -11,9 +11,14 @@
 /**
  * The `@key` directive is used to indicate a combination of fields that can be used to uniquely
  * identify and fetch an object or interface.
+ *
+ * @see https://www.apollographql.com/docs/federation/federated-types/federated-directives/#key
  */
 class KeyDirective extends Directive
 {
+    public const ARGUMENT_FIELDS = 'fields';
+    public const ARGUMENT_RESOLVABLE = 'resolvable';
+
     public function __construct()
     {
         parent::__construct([
@@ -21,9 +26,13 @@ public function __construct()
             'locations' => [DirectiveLocation::OBJECT, DirectiveLocation::IFACE],
             'args' => [
                 new FieldArgument([
-                    'name' => 'fields',
+                    'name' => self::ARGUMENT_FIELDS,
                     'type' => Type::nonNull(Type::string()),
                 ]),
+                new FieldArgument([
+                    'name' => self::ARGUMENT_RESOLVABLE,
+                    'type' => Type::boolean(),
+                ]),
             ],
         ]);
     }
diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 8ce2c7c..bbb6ec1 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -36,7 +36,7 @@
  *         'firstName' => [...],
  *         'lastName' => [...],
  *       ],
- *       'keyFields' => ['id', 'email']
+ *       'keys' => [['fields' => 'id'], ['fields' => 'email']]
  *     ]);
  *
  *     $queryType = new GraphQL\Type\Definition\ObjectType([
diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index db3a72b..5d694ec 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -22,7 +22,7 @@
  * <code>
  *     $userType = new Apollo\Federation\Types\EntityObjectType([
  *       'name' => 'User',
- *       'keyFields' => ['id', 'email'],
+ *       'keys' => [['fields' => 'id'], ['fields' => 'email']],
  *       'fields' => [...]
  *     ]);
  * </code>
@@ -31,7 +31,7 @@
  * <code>
  *     $userType = new Apollo\Federation\Types\EntityObjectType([
  *       'name' => 'User',
- *       'keyFields' => ['id', 'email'],
+ *       'keys' => [['fields' => 'id', 'resolvable': false ]],
  *       'fields' => [
  *         'id' => [
  *           'type' => Types::int(),
@@ -43,7 +43,7 @@
  */
 class EntityObjectType extends ObjectType
 {
-    public const FIELD_KEY_FIELDS = 'keyFields';
+    public const FIELD_KEYS = 'keys';
     public const FIELD_REFERENCE_RESOLVER = '__resolveReference';
 
     public const FIELD_DIRECTIVE_IS_EXTERNAL = 'isExternal';
@@ -54,16 +54,22 @@ class EntityObjectType extends ObjectType
     public $referenceResolver = null;
 
     /**
-     * @var array<int,string>|array<int|string,string|array<int|string,mixed>>
+     * @var array<int,array{fields: array<int,string>|array<int|string,string|array<int|string,mixed>>, resolvable: bool }>
      */
-    private array $keyFields;
+    private array $keys;
 
     /**
      * @param array<string,mixed> $config
      */
     public function __construct(array $config)
     {
-        $this->keyFields = $config[self::FIELD_KEY_FIELDS];
+        Utils::invariant(
+            !(\array_key_exists(self::FIELD_KEYS, $config) && \array_key_exists('keyFields', $config)),
+            'Use only one way to define directives @key.'
+        );
+
+        $this->keys = $config[self::FIELD_KEYS]
+            ?? array_map(static fn ($x): array => ['fields' => $x], $config['keyFields']);
 
         if (isset($config[self::FIELD_REFERENCE_RESOLVER])) {
             self::validateResolveReference($config);
@@ -76,11 +82,30 @@ public function __construct(array $config)
     /**
      * Gets the fields that serve as the unique key or identifier of the entity.
      *
+     * @deprecated Use {@see getKeys()}
+     *
      * @return array<int,string>|array<int|string,string|array<int|string,mixed>>
      */
     public function getKeyFields(): array
     {
-        return $this->keyFields;
+        @trigger_error(
+            'Since skillshare/apollo-federation-php 2.0.0: '
+            . 'Method \Apollo\Federation\Types\EntityObjectType::getKeyFields() is deprecated. '
+            . 'Use \Apollo\Federation\Types\EntityObjectType::getKeys() instead of it.',
+            \E_USER_DEPRECATED
+        );
+
+        return array_map(static fn(array $x) => $x['fields'], $this->keys);
+    }
+
+    /**
+     * Gets the fields that serve as the unique key or identifier of the entity.
+     *
+     * @return array<int,array{fields: array<int,string>|array<int|string,string|array<int|string,mixed>>, resolvable: bool }>
+     */
+    public function getKeys(): array
+    {
+        return $this->keys;
     }
 
     /**
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index a90d94a..d541e20 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -31,6 +31,7 @@
 
 namespace Apollo\Federation\Utils;
 
+use Apollo\Federation\Directives\KeyDirective;
 use Apollo\Federation\Enum\DirectiveEnum;
 use Apollo\Federation\FederatedSchema;
 use Apollo\Federation\Types\EntityObjectType;
@@ -192,8 +193,12 @@ protected static function printKeyDirective(EntityObjectType $type): string
     {
         $keyDirective = '';
 
-        foreach ($type->getKeyFields() as $keyField) {
-            $keyDirective .= sprintf(' @key(fields: "%s")', static::printKeyFields($keyField));
+        foreach ($type->getKeys() as $keyField) {
+            $arguments = [sprintf('%s: "%s"', KeyDirective::ARGUMENT_FIELDS, static::printKeyFields($keyField['fields']))];
+            if (\array_key_exists('resolvable', $keyField)) {
+                $arguments[] = sprintf('%s: %s', KeyDirective::ARGUMENT_RESOLVABLE, $keyField['resolvable'] ? 'true' : 'false');
+            }
+            $keyDirective .= sprintf(' @key(%s)', implode(', ', $arguments));
         }
 
         return $keyDirective;
diff --git a/test/EntitiesTest.php b/test/EntitiesTest.php
index 9c03f73..f0b4c42 100644
--- a/test/EntitiesTest.php
+++ b/test/EntitiesTest.php
@@ -16,11 +16,11 @@ class EntitiesTest extends TestCase
 
     public function testCreatingEntityType(): void
     {
-        $expectedKeyFields = ['id', 'email'];
+        $expectedKeys = [['fields' => 'id'], ['fields' => 'email']];
 
         $userType = new EntityObjectType([
             'name' => 'User',
-            'keyFields' => $expectedKeyFields,
+            'keys' => $expectedKeys,
             'fields' => [
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
@@ -29,17 +29,17 @@ public function testCreatingEntityType(): void
             ],
         ]);
 
-        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
+        $this->assertEqualsCanonicalizing($expectedKeys, $userType->getKeys());
         $this->assertMatchesSnapshot($userType->config);
     }
 
     public function testCreatingEntityTypeWithCallable(): void
     {
-        $expectedKeyFields = ['id', 'email'];
+        $expectedKeys = [['fields' => 'id'], ['fields' => 'email']];
 
         $userType = new EntityObjectType([
             'name' => 'User',
-            'keyFields' => $expectedKeyFields,
+            'keys' => $expectedKeys,
             'fields' => function () {
                 return [
                     'id' => ['type' => Type::int()],
@@ -50,7 +50,7 @@ public function testCreatingEntityTypeWithCallable(): void
             },
         ]);
 
-        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
+        $this->assertEqualsCanonicalizing($expectedKeys, $userType->getKeys());
         $this->assertMatchesSnapshot($userType->config);
     }
 
@@ -66,7 +66,7 @@ public function testResolvingEntityReference(): void
 
         $userType = new EntityObjectType([
             'name' => 'User',
-            'keyFields' => ['id', 'email'],
+            'keys' => [['fields' => 'id'], ['fields' => 'email']],
             'fields' => [
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
@@ -85,18 +85,18 @@ public function testResolvingEntityReference(): void
 
     public function testCreatingEntityRefType(): void
     {
-        $expectedKeyFields = ['id', 'email'];
+        $expectedKeys = [['fields' => 'id', 'resolvable' => false]];
 
         $userType = new EntityRefObjectType([
             'name' => 'User',
-            'keyFields' => $expectedKeyFields,
+            'keys' => $expectedKeys,
             'fields' => [
                 'id' => ['type' => Type::int()],
                 'email' => ['type' => Type::string()],
             ],
         ]);
 
-        $this->assertEqualsCanonicalizing($expectedKeyFields, $userType->getKeyFields());
+        $this->assertEqualsCanonicalizing($expectedKeys, $userType->getKeys());
         $this->assertMatchesSnapshot($userType->config);
     }
 }
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index 6786d4b..5673e89 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -83,7 +83,7 @@ private static function getEpisodeType(): EntityObjectType
                     'provides' => 'name',
                 ],
             ],
-            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
+            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
             EntityObjectType::FIELD_REFERENCE_RESOLVER => static function (array $ref): array {
                 $entity = StarWarsData::getEpisodeById($ref['id']);
                 $entity['__typename'] = 'Episode';
@@ -113,7 +113,7 @@ private static function getCharacterType(): EntityRefObjectType
                     'requires' => 'name',
                 ],
             ],
-            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
+            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
         ]);
     }
 
@@ -132,7 +132,7 @@ private static function getLocationType(): EntityRefObjectType
                     'isExternal' => true,
                 ],
             ],
-            EntityObjectType::FIELD_KEY_FIELDS => ['id'],
+            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
         ]);
     }
 }
diff --git a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
index 6f55ba2..6444549 100644
--- a/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
+++ b/test/__snapshots__/DirectivesTest__testItAddsDirectivesToSchema__1.txt
@@ -2,7 +2,7 @@ directive @external on FIELD_DEFINITION
 
 directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
 
-directive @key(fields: String!) on OBJECT | INTERFACE
+directive @key(fields: String!, resolvable: Boolean) on OBJECT | INTERFACE
 
 directive @link(url: String!, as: String, for: String, import: [link_Import!]) repeatable on SCHEMA
 
diff --git a/test/__snapshots__/EntitiesTest__testCreatingEntityRefType__1.yml b/test/__snapshots__/EntitiesTest__testCreatingEntityRefType__1.yml
index 3bc1453..036ee5e 100644
--- a/test/__snapshots__/EntitiesTest__testCreatingEntityRefType__1.yml
+++ b/test/__snapshots__/EntitiesTest__testCreatingEntityRefType__1.yml
@@ -1,7 +1,6 @@
 name: User
-keyFields:
-    - id
-    - email
+keys:
+    - { fields: id, resolvable: false }
 fields:
     id: { type: { name: Int, description: "The `Int` scalar type represents non-fractional signed whole numeric\nvalues. Int can represent values between -(2^31) and 2^31 - 1. ", astNode: null, extensionASTNodes: null, config: {  } } }
     email: { type: { name: String, description: "The `String` scalar type represents textual data, represented as UTF-8\ncharacter sequences. The String type is most often used by GraphQL to\nrepresent free-form human-readable text.", astNode: null, extensionASTNodes: null, config: {  } } }
diff --git a/test/__snapshots__/EntitiesTest__testCreatingEntityTypeWithCallable__1.yml b/test/__snapshots__/EntitiesTest__testCreatingEntityTypeWithCallable__1.yml
index 550a52f..525bd68 100644
--- a/test/__snapshots__/EntitiesTest__testCreatingEntityTypeWithCallable__1.yml
+++ b/test/__snapshots__/EntitiesTest__testCreatingEntityTypeWithCallable__1.yml
@@ -1,5 +1,5 @@
 name: User
-keyFields:
-    - id
-    - email
+keys:
+    - { fields: id }
+    - { fields: email }
 fields: {  }
diff --git a/test/__snapshots__/EntitiesTest__testCreatingEntityType__1.yml b/test/__snapshots__/EntitiesTest__testCreatingEntityType__1.yml
index e073da4..2b18be2 100644
--- a/test/__snapshots__/EntitiesTest__testCreatingEntityType__1.yml
+++ b/test/__snapshots__/EntitiesTest__testCreatingEntityType__1.yml
@@ -1,7 +1,7 @@
 name: User
-keyFields:
-    - id
-    - email
+keys:
+    - { fields: id }
+    - { fields: email }
 fields:
     id: { type: { name: Int, description: "The `Int` scalar type represents non-fractional signed whole numeric\nvalues. Int can represent values between -(2^31) and 2^31 - 1. ", astNode: null, extensionASTNodes: null, config: {  } } }
     email: { type: { name: String, description: "The `String` scalar type represents textual data, represented as UTF-8\ncharacter sequences. The String type is most often used by GraphQL to\nrepresent free-form human-readable text.", astNode: null, extensionASTNodes: null, config: {  } } }
diff --git a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
index 7718755..2af0a85 100644
--- a/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
+++ b/test/__snapshots__/SchemaTest__testSchemaSdl__1.txt
@@ -2,7 +2,7 @@ directive @external on FIELD_DEFINITION
 
 directive @inaccessible on FIELD_DEFINITION | INTERFACE | OBJECT | UNION
 
-directive @key(fields: String!) on OBJECT | INTERFACE
+directive @key(fields: String!, resolvable: Boolean) on OBJECT | INTERFACE
 
 directive @link(url: String!, as: String, for: String, import: [link_Import!]) repeatable on SCHEMA
 

From 970ca0b286c3b157d37392874d0503a78856fa16 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 13:01:40 +0300
Subject: [PATCH 26/40] Extend validation of type reference

---
 src/Types/EntityObjectType.php | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index 5d694ec..f58cf47 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -143,7 +143,11 @@ private function validateReferenceResolver(): void
      */
     private function validateReferenceKeys(array $ref): void
     {
-        Utils::invariant(isset($ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME]), 'Type name must be provided in the reference.');
+        Utils::invariant(
+            isset($ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME])
+            && $ref[FederatedSchema::RESERVED_FIELD_TYPE_NAME] === $this->config['name'],
+            'Type name must be provided in the reference.'
+        );
     }
 
     /**

From 75f8b3ae00fcd40b81bd8214f4712d668a65e477 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 2 Aug 2022 19:29:26 +0300
Subject: [PATCH 27/40] Add validation if Referenced entity has only one @key
 directive.

---
 README.md                                     |  2 +-
 src/Types/EntityRefObjectType.php             | 23 ++++++++
 test/EntitiesTest.php                         | 57 +++++++++++++++++++
 test/StarWarsSchema.php                       |  6 +-
 .../SchemaTest__testServiceSdl__1.yml         |  2 +-
 5 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index f03f5db..a477d60 100644
--- a/README.md
+++ b/README.md
@@ -50,7 +50,7 @@ use Apollo\Federation\Types\EntityRefObjectType;
 
 $userType = new EntityRefObjectType([
     'name' => 'User',
-    'keys' => [['fields' => 'id'], ['fields' => 'email']],
+    'keys' => [['fields' => 'id', 'resolvable' => false]],
     'fields' => [
         'id' => ['type' => Type::int()],
         'email' => ['type' => Type::string()]
diff --git a/src/Types/EntityRefObjectType.php b/src/Types/EntityRefObjectType.php
index 3789755..a6201d8 100644
--- a/src/Types/EntityRefObjectType.php
+++ b/src/Types/EntityRefObjectType.php
@@ -4,12 +4,35 @@
 
 namespace Apollo\Federation\Types;
 
+use GraphQL\Utils\Utils;
+
 /**
  * An entity reference is a type referencing an entity owned by another service. Usually,
  * entity references are stub types containing only the key fields necessary for the
  * Apollo Gateway {@see https://www.apollographql.com/docs/intro/platform/#gateway } to
  * resolve the entity during query execution.
+ *
+ * @see https://www.apollographql.com/docs/federation/v1/entities#referencing-entities
  */
 class EntityRefObjectType extends EntityObjectType
 {
+    public function __construct(array $config)
+    {
+        parent::__construct($config);
+
+        $keys = $this->getKeys();
+        Utils::invariant(
+            1 === \count($keys),
+            'There is invalid config of %s. Referenced entity must have exactly one directive @key.',
+            $this->name
+        );
+
+        /** @var array<string,mixed> $key */
+        $key = reset($keys);
+        Utils::invariant(
+            \array_key_exists('resolvable', $key) && false === $key['resolvable'],
+            'There is invalid config of %s. Referenced entity directive @key must have argument "resolvable" with value `false`.',
+            $this->name
+        );
+    }
 }
diff --git a/test/EntitiesTest.php b/test/EntitiesTest.php
index f0b4c42..1e480f6 100644
--- a/test/EntitiesTest.php
+++ b/test/EntitiesTest.php
@@ -6,6 +6,7 @@
 
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
+use GraphQL\Error\InvariantViolation;
 use GraphQL\Type\Definition\Type;
 use PHPUnit\Framework\TestCase;
 use Spatie\Snapshots\MatchesSnapshots;
@@ -99,4 +100,60 @@ public function testCreatingEntityRefType(): void
         $this->assertEqualsCanonicalizing($expectedKeys, $userType->getKeys());
         $this->assertMatchesSnapshot($userType->config);
     }
+
+    /**
+     * @doesNotPerformAssertions
+     * @dataProvider getDataEntityRefObjectTypeWithSingleKeys
+     *
+     * @param array<string,mixed> $config
+     */
+    public function testEntityRefObjectTypeDoesNotThrowsErrorOnSingleKeys(array $config): void
+    {
+        new EntityRefObjectType($config);
+    }
+
+    /**
+     * @dataProvider getDataEntityRefObjectTypeWithMultipleKeys
+     *
+     * @param array<string,mixed> $config
+     */
+    public function testEntityRefObjectTypeThrowsErrorOnMultipleKeys(array $config): void
+    {
+        $this->expectException(InvariantViolation::class);
+        $this->expectExceptionMessage('There is invalid config of EntityRefObject. Referenced entity must have exactly one directive @key.');
+        new EntityRefObjectType($config);
+    }
+
+    /**
+     * @dataProvider getDataWithInvalidResolvableArgument
+     *
+     * @param array<string,mixed> $config
+     */
+    public function testEntityRefObjectTypeThrowsErrorOnInvalidResolvableArgument(array $config): void
+    {
+        $this->expectException(InvariantViolation::class);
+        $this->expectExceptionMessage('There is invalid config of EntityRefObject. Referenced entity directive @key must have argument "resolvable" with value `false`.');
+        new EntityRefObjectType($config);
+    }
+
+    public function getDataEntityRefObjectTypeWithMultipleKeys(): \Generator
+    {
+        yield [['keys' => [['fields' => 'id'], ['fields' => 'id2']]]];
+        yield [['keys' => [['fields' => 'id'], ['fields' => 'id2'], ['fields' => 'id2']]]];
+    }
+
+    public function getDataEntityRefObjectTypeWithSingleKeys(): \Generator
+    {
+        yield [['keys' => [['fields' => 'id', 'resolvable' => false]]]];
+        yield [['keys' => [['fields' => ['obj' => 'id'], 'resolvable' => false]]]];
+    }
+
+    public function getDataWithInvalidResolvableArgument(): \Generator
+    {
+        yield [['keys' => [['fields' => 'id']]]];
+        yield [['keys' => [['fields' => 'id', 'resolvable' => true]]]];
+        yield [['keys' => [['fields' => 'id', 'resolvable' => 0]]]];
+        yield [['keys' => [['fields' => 'id', 'resolvable' => 'no']]]];
+        yield [['keys' => [['fields' => 'id', 'resolvable' => 'false']]]];
+    }
 }
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index 5673e89..f6c1d71 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -83,7 +83,7 @@ private static function getEpisodeType(): EntityObjectType
                     'provides' => 'name',
                 ],
             ],
-            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
+            EntityObjectType::FIELD_KEYS => [['fields' => 'id']],
             EntityObjectType::FIELD_REFERENCE_RESOLVER => static function (array $ref): array {
                 $entity = StarWarsData::getEpisodeById($ref['id']);
                 $entity['__typename'] = 'Episode';
@@ -113,7 +113,7 @@ private static function getCharacterType(): EntityRefObjectType
                     'requires' => 'name',
                 ],
             ],
-            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
+            EntityObjectType::FIELD_KEYS => [['fields' => 'id', 'resolvable' => false]],
         ]);
     }
 
@@ -132,7 +132,7 @@ private static function getLocationType(): EntityRefObjectType
                     'isExternal' => true,
                 ],
             ],
-            EntityObjectType::FIELD_KEYS => ['fields' => 'id'],
+            EntityObjectType::FIELD_KEYS => [['fields' => 'id', 'resolvable' => false]],
         ]);
     }
 }
diff --git a/test/__snapshots__/SchemaTest__testServiceSdl__1.yml b/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
index 799ec1c..588e21c 100644
--- a/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
+++ b/test/__snapshots__/SchemaTest__testServiceSdl__1.yml
@@ -1,2 +1,2 @@
 data:
-    _service: { sdl: "\"\"\"A character in the Star Wars Trilogy\"\"\"\nextend type Character @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n  locations: [Location]! @requires(fields: \"name\")\n}\n\n\"\"\"A film in the Star Wars Trilogy\"\"\"\ntype Episode @key(fields: \"id\") {\n  id: Int! \n  title: String! \n  characters: [Character!]! @provides(fields: \"name\")\n}\n\n\"\"\"A location in the Star Wars Trilogy\"\"\"\nextend type Location @key(fields: \"id\") {\n  id: Int! @external\n  name: String! @external\n}\n\nextend type Query {\n  episodes: [Episode!]! \n  deprecatedEpisodes: [Episode!]! @deprecated(reason: \"Because you should use the other one.\") \n}\n\nscalar link_Import\n" }
+    _service: { sdl: "\"\"\"A character in the Star Wars Trilogy\"\"\"\nextend type Character @key(fields: \"id\", resolvable: false) {\n  id: Int! @external\n  name: String! @external\n  locations: [Location]! @requires(fields: \"name\")\n}\n\n\"\"\"A film in the Star Wars Trilogy\"\"\"\ntype Episode @key(fields: \"id\") {\n  id: Int! \n  title: String! \n  characters: [Character!]! @provides(fields: \"name\")\n}\n\n\"\"\"A location in the Star Wars Trilogy\"\"\"\nextend type Location @key(fields: \"id\", resolvable: false) {\n  id: Int! @external\n  name: String! @external\n}\n\nextend type Query {\n  episodes: [Episode!]! \n  deprecatedEpisodes: [Episode!]! @deprecated(reason: \"Because you should use the other one.\") \n}\n\nscalar link_Import\n" }

From 86ae658c894671cdd36485d028bf9ae9e365d8b5 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Thu, 4 Aug 2022 17:24:55 +0300
Subject: [PATCH 28/40] Rename file "phpunit.xml" to "phpunit.xml.dist" to
 stick to standard testing configuration files pattern and permit safe
 overriding configs in local environment.

---
 .gitignore                      | 3 ++-
 phpunit.xml => phpunit.xml.dist | 0
 2 files changed, 2 insertions(+), 1 deletion(-)
 rename phpunit.xml => phpunit.xml.dist (100%)

diff --git a/.gitignore b/.gitignore
index f5aea2f..f05fec2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,4 +3,5 @@ composer.phar
 /vendor/
 /node_modules/
 *.cache
-cov.xml
\ No newline at end of file
+cov.xml
+phpunit.xml
\ No newline at end of file
diff --git a/phpunit.xml b/phpunit.xml.dist
similarity index 100%
rename from phpunit.xml
rename to phpunit.xml.dist

From ae58a6ee263a0e02bfda4924fe5ad1a033516fad Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 5 Aug 2022 16:47:12 +0300
Subject: [PATCH 29/40] Extract getting of required federated directives to the
 schema builder

---
 src/FederatedSchema.php      |  3 +--
 src/FederatedSchemaTrait.php | 18 ------------------
 src/SchemaBuilder.php        | 34 ++++++++++++++++++++++++++++++++++
 test/StarWarsSchema.php      | 10 ++++++++--
 4 files changed, 43 insertions(+), 22 deletions(-)
 create mode 100644 src/SchemaBuilder.php

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index bbb6ec1..7a7e8d1 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -81,10 +81,9 @@ public static function isReservedRootType(string $name): bool
     public function __construct(array $config)
     {
         $this->entityTypes = $this->extractEntityTypes($config);
-        $this->entityDirectives = Directives::getDirectives();
         $this->schemaExtensionTypes = $this->extractSchemaExtensionTypes($config);
 
-        $config = array_merge($config, $this->getEntityDirectivesConfig($config), $this->getQueryTypeConfig($config));
+        $config = array_merge($config, $this->getQueryTypeConfig($config));
 
         parent::__construct($config);
     }
diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index 6942362..781a629 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -28,11 +28,6 @@ trait FederatedSchemaTrait
      */
     protected array $schemaExtensionTypes = [];
 
-    /**
-     * @var Directive[]
-     */
-    protected array $entityDirectives = [];
-
     /**
      * Returns all the resolved entity types in the schema.
      *
@@ -59,19 +54,6 @@ public function getSchemaExtensionTypes(): array
         return $this->schemaExtensionTypes;
     }
 
-    /**
-     * @param array<string,mixed> $config
-     *
-     * @return array<string,mixed>
-     */
-    protected function getEntityDirectivesConfig(array $config): array
-    {
-        $directives = $config['directives'] ?? [];
-        $config['directives'] = array_merge($directives, $this->entityDirectives);
-
-        return $config;
-    }
-
     /**
      * @param array{ query: ObjectType } $config
      *
diff --git a/src/SchemaBuilder.php b/src/SchemaBuilder.php
new file mode 100644
index 0000000..255a8d4
--- /dev/null
+++ b/src/SchemaBuilder.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation;
+
+class SchemaBuilder
+{
+    /**
+     * @param array<string,mixed> $schemaConfig
+     * @param array<string,mixed> $builderConfig
+     */
+    public function build(array $schemaConfig, array $builderConfig = []): FederatedSchema
+    {
+        $builderConfig += ['directives' => ['link']];
+        $schemaConfig = array_merge($schemaConfig, $this->getEntityDirectivesConfig($schemaConfig, $builderConfig));
+
+        return new FederatedSchema($schemaConfig);
+    }
+
+    /**
+     * @param array<string,mixed> $schemaConfig
+     * @param array{ directives: array<string> } $builderConfig
+     *
+     * @return array<string,mixed>
+     */
+    protected function getEntityDirectivesConfig(array $schemaConfig, array $builderConfig): array
+    {
+        $directives = array_intersect_key(Directives::getDirectives(), array_flip($builderConfig['directives']));
+        $schemaConfig['directives'] = array_merge($schemaConfig['directives'] ?? [], $directives);
+
+        return $schemaConfig;
+    }
+}
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index f6c1d71..927747b 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -4,7 +4,9 @@
 
 namespace Apollo\Federation\Tests;
 
+use Apollo\Federation\Enum\DirectiveEnum;
 use Apollo\Federation\FederatedSchema;
+use Apollo\Federation\SchemaBuilder;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
 use GraphQL\Type\Definition\ObjectType;
@@ -18,8 +20,10 @@ class StarWarsSchema
     public static function getEpisodesSchema(): FederatedSchema
     {
         if (!self::$episodesSchema) {
-            self::$episodesSchema = new FederatedSchema([
+            self::$episodesSchema = (new SchemaBuilder())->build([
                 'query' => self::getQueryType(),
+            ], [
+                'directives' => DirectiveEnum::getAll(),
             ]);
         }
 
@@ -29,7 +33,7 @@ public static function getEpisodesSchema(): FederatedSchema
     public static function getEpisodesSchemaCustomResolver(): FederatedSchema
     {
         if (!self::$overriddenEpisodesSchema) {
-            self::$overriddenEpisodesSchema = new FederatedSchema([
+            self::$overriddenEpisodesSchema = (new SchemaBuilder())->build([
                 'query' => self::getQueryType(),
                 'resolve' => function ($root, $args, $context, $info): array {
                     return array_map(static function (array $ref) use ($info) {
@@ -40,6 +44,8 @@ public static function getEpisodesSchemaCustomResolver(): FederatedSchema
                         return $type->resolveReference($ref);
                     }, $args[FederatedSchema::RESERVED_FIELD_REPRESENTATIONS]);
                 },
+            ], [
+                'directives' => DirectiveEnum::getAll(),
             ]);
         }
 

From 78ba78c1054d1cec4f01435a2411897aee3a379e Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 5 Aug 2022 20:32:51 +0300
Subject: [PATCH 30/40] Fix extendability of schema

---
 src/FederatedSchemaTrait.php | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index 781a629..c7e36ec 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -166,6 +166,24 @@ protected function resolve($root, $args, $context, $info): array
         }, $args[FederatedSchema::RESERVED_FIELD_REPRESENTATIONS]);
     }
 
+    /**
+     * @param array<string,mixed> $config
+     *
+     * @return array<Type>
+     */
+    protected function extractExtraTypes(array $config): array
+    {
+        $typeMap = [];
+        $configTypes = $config['types'] ?? [];
+        if (\is_array($configTypes)) {
+            $typeMap = $configTypes;
+        } elseif (\is_callable($configTypes)) {
+            $typeMap = $configTypes();
+        }
+
+        return $typeMap;
+    }
+
     /**
      * @param array<string,mixed> $config
      *
@@ -192,17 +210,8 @@ protected function extractEntityTypes(array $config): array
      */
     protected function extractSchemaExtensionTypes(array $config): array
     {
-        $typeMap = [];
-        $configTypes = $config['types'] ?? [];
-        if (\is_array($configTypes)) {
-            $typeMap = $configTypes;
-        } elseif (\is_callable($configTypes)) {
-            $typeMap = $configTypes();
-        }
-
         $types = [];
-
-        foreach ($typeMap as $type) {
+        foreach ($this->extractExtraTypes($config) as $type) {
             if ($type instanceof SchemaExtensionType) {
                 $types[$type->name] = $type;
             }

From fe7456cc80fdd5c27217827fe4b635eb0fce72f8 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 29 Aug 2022 17:59:35 +0300
Subject: [PATCH 31/40] Update phpdoc

---
 src/Types/EntityObjectType.php    | 2 ++
 src/Types/EntityRefObjectType.php | 1 +
 2 files changed, 3 insertions(+)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index f58cf47..e0e05a8 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -85,6 +85,8 @@ public function __construct(array $config)
      * @deprecated Use {@see getKeys()}
      *
      * @return array<int,string>|array<int|string,string|array<int|string,mixed>>
+     *
+     * @codeCoverageIgnore
      */
     public function getKeyFields(): array
     {
diff --git a/src/Types/EntityRefObjectType.php b/src/Types/EntityRefObjectType.php
index a6201d8..98dcf0f 100644
--- a/src/Types/EntityRefObjectType.php
+++ b/src/Types/EntityRefObjectType.php
@@ -13,6 +13,7 @@
  * resolve the entity during query execution.
  *
  * @see https://www.apollographql.com/docs/federation/v1/entities#referencing-entities
+ * @see https://www.apollographql.com/docs/federation/entities#referencing-an-entity-without-contributing-fields
  */
 class EntityRefObjectType extends EntityObjectType
 {

From 408c3e19f40dfc35cbf99b688e231c9f2c7118b2 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 29 Aug 2022 18:10:08 +0300
Subject: [PATCH 32/40] Remove deprecated excess classes imports

---
 src/FederatedSchema.php | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/src/FederatedSchema.php b/src/FederatedSchema.php
index 7a7e8d1..d0ae2b3 100644
--- a/src/FederatedSchema.php
+++ b/src/FederatedSchema.php
@@ -4,17 +4,7 @@
 
 namespace Apollo\Federation;
 
-use Apollo\Federation\Types\EntityObjectType;
-use Apollo\Federation\Utils\FederatedSchemaPrinter;
-use GraphQL\Type\Definition\CustomScalarType;
-use GraphQL\Type\Definition\Directive;
-use GraphQL\Type\Definition\ListOfType;
-use GraphQL\Type\Definition\ObjectType;
-use GraphQL\Type\Definition\Type;
-use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Schema;
-use GraphQL\Utils\TypeInfo;
-use GraphQL\Utils\Utils;
 
 /**
  * A federated GraphQL schema definition see related docs {@see https://www.apollographql.com/docs/apollo-server/federation/introduction }.

From 07a0f9e80b0ef891ce68fa4d9f69d1eada721679 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Mon, 29 Aug 2022 18:18:02 +0300
Subject: [PATCH 33/40] Fix merge conflict: make updates equivalent to the
 commit 4f958ddb683c1fceb1d162f58a5dc2957e26fe5d

---
 src/SchemaBuilder.php   | 5 +++++
 test/StarWarsSchema.php | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/src/SchemaBuilder.php b/src/SchemaBuilder.php
index 255a8d4..cda327a 100644
--- a/src/SchemaBuilder.php
+++ b/src/SchemaBuilder.php
@@ -4,6 +4,8 @@
 
 namespace Apollo\Federation;
 
+use GraphQL\Type\Definition\Directive;
+
 class SchemaBuilder
 {
     /**
@@ -27,6 +29,9 @@ public function build(array $schemaConfig, array $builderConfig = []): Federated
     protected function getEntityDirectivesConfig(array $schemaConfig, array $builderConfig): array
     {
         $directives = array_intersect_key(Directives::getDirectives(), array_flip($builderConfig['directives']));
+        if (array_intersect_key($directives, Directive::getInternalDirectives())) {
+            throw new \LogicException('Some Apollo directives override internals.');
+        }
         $schemaConfig['directives'] = array_merge($schemaConfig['directives'] ?? [], $directives);
 
         return $schemaConfig;
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index 927747b..f04e48f 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -9,6 +9,7 @@
 use Apollo\Federation\SchemaBuilder;
 use Apollo\Federation\Types\EntityObjectType;
 use Apollo\Federation\Types\EntityRefObjectType;
+use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
 
@@ -21,6 +22,7 @@ public static function getEpisodesSchema(): FederatedSchema
     {
         if (!self::$episodesSchema) {
             self::$episodesSchema = (new SchemaBuilder())->build([
+                'directives' => Directive::getInternalDirectives(),
                 'query' => self::getQueryType(),
             ], [
                 'directives' => DirectiveEnum::getAll(),
@@ -34,6 +36,7 @@ public static function getEpisodesSchemaCustomResolver(): FederatedSchema
     {
         if (!self::$overriddenEpisodesSchema) {
             self::$overriddenEpisodesSchema = (new SchemaBuilder())->build([
+                'directives' => Directive::getInternalDirectives(),
                 'query' => self::getQueryType(),
                 'resolve' => function ($root, $args, $context, $info): array {
                     return array_map(static function (array $ref) use ($info) {

From a34d3361d0c1e16cac99a40885cbb7cd4ff37162 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Tue, 30 Aug 2022 09:06:05 +0300
Subject: [PATCH 34/40] Fix documentation

---
 README.md                      | 8 ++++----
 src/Types/EntityObjectType.php | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index a477d60..7f6143a 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ composer require skillshare/apollo-federation-php
 
 ### Entities
 
-An entity is an object type that you define canonically in one subgraph and can then reference and extend in other subgraphs. It can be defined via the `EntityObjectType` which takes the same configuration as the default `ObjectType` plus a `keyFields` and `__resolveReference` properties. 
+An entity is an object type that you define canonically in one subgraph and can then reference and extend in other subgraphs. It can be defined via the `EntityObjectType` which takes the same configuration as the default `ObjectType` plus a `keys` and `__resolveReference` properties. 
 
 ```php
 use Apollo\Federation\Types\EntityObjectType;
@@ -29,13 +29,13 @@ $userType = new EntityObjectType([
         'firstName' => ['type' => Type::string()],
         'lastName' => ['type' => Type::string()]
     ],
-    '__resolveReference' => static function ($ref) {
-        // .. fetch from a data source.
+    '__resolveReference' => function ($ref) {
+        // ... fetch from a data source.
     }
 ]);
 ```
 
-* `keys` — defines the entity's primary key, which consists of one or more of the fields. An entity's key cannot include fields that return a union or interface.
+* `keys` — defines the entity's unique keys, which consists of one or more of the fields. An entity's key cannot include fields that return a union or interface.
 
 * `__resolveReference` — resolves the representation of the entity from the provided reference. Subgraphs use representations to reference entities from other subgraphs. A representation requires only an explicit __typename definition and values for the entity's primary key fields.
 
diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index e0e05a8..f20710a 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -15,7 +15,7 @@
  * of the type, similar to the function of a primary key in a SQL table
  * see related docs {@see https://www.apollographql.com/docs/apollo-server/federation/core-concepts/#entities-and-keys }.
  *
- * The `keyFields` property is required in the configuration, indicating the fields that
+ * The `keys` property is required in the configuration, indicating the fields that
  * serve as the unique keys or identifiers of the entity.
  *
  * Sample usage:

From edce7284cad70afb8acfb87e8d69c13240e6c8b5 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Wed, 7 Sep 2022 21:30:00 +0300
Subject: [PATCH 35/40] Implement tests

---
 phpunit.xml.dist    |  5 ++++-
 test/EntityTest.php | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 test/EntityTest.php

diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 75731ed..55389c4 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd" bootstrap="test/Bootstrap.php">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="test/Bootstrap.php"
+>
   <coverage>
     <include>
       <directory suffix=".php">./src</directory>
diff --git a/test/EntityTest.php b/test/EntityTest.php
new file mode 100644
index 0000000..8b62068
--- /dev/null
+++ b/test/EntityTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Apollo\Federation\Tests;
+
+use Apollo\Federation\Types\EntityObjectType;
+use GraphQL\Error\InvariantViolation;
+use PHPUnit\Framework\TestCase;
+
+final class EntityTest extends TestCase
+{
+    public function testConstructorsThrowsExceptionOnDuplicatedKeysConfig(): void
+    {
+        $this->expectException(InvariantViolation::class);
+        $config = ['keys' => [], 'keyFields' => [], 'name' => '*'];
+        new EntityObjectType($config);
+    }
+
+    public function testMethodGetKeyFieldsTriggersDeprecation(): void
+    {
+        $isCaught = false;
+        set_error_handler(static function (int $errno, string $errstr, string $errfile = '', int $errline = 0, array $errcontext = []) use (&$isCaught): bool {
+            $isCaught = true;
+            return true;
+        });
+        $config = ['name' => '*', 'keys' => [['fields' => ['id']]]];
+        (new EntityObjectType($config))->getKeyFields();
+
+        self::assertTrue($isCaught, 'It does trigger deprecation error. But it should!');
+
+        restore_error_handler();
+    }
+}
\ No newline at end of file

From 3562fe3769b975771fe39f1d24f61e9d1bbd531c Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Wed, 7 Sep 2022 21:41:51 +0300
Subject: [PATCH 36/40] Implement tests

---
 src/Types/EntityObjectType.php |  2 +-
 test/EntityTest.php            | 47 +++++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index f20710a..f92ac6a 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -97,7 +97,7 @@ public function getKeyFields(): array
             \E_USER_DEPRECATED
         );
 
-        return array_map(static fn(array $x) => $x['fields'], $this->keys);
+        return array_merge(...array_map(static fn(array $x): array => (array) $x['fields'], $this->keys));
     }
 
     /**
diff --git a/test/EntityTest.php b/test/EntityTest.php
index 8b62068..e759ff2 100644
--- a/test/EntityTest.php
+++ b/test/EntityTest.php
@@ -17,11 +17,24 @@ public function testConstructorsThrowsExceptionOnDuplicatedKeysConfig(): void
         new EntityObjectType($config);
     }
 
+    /**
+     * @dataProvider getDataForTestMethodGetKeyFields
+     *
+     * @param string[] $expected
+     * @param array<string,mixed> $config
+     */
+    public function testMethodGetKeyFields(array $expected, array $config): void
+    {
+        self::assertSame($expected, (new EntityObjectType($config))->getKeyFields());
+    }
+
     public function testMethodGetKeyFieldsTriggersDeprecation(): void
     {
         $isCaught = false;
-        set_error_handler(static function (int $errno, string $errstr, string $errfile = '', int $errline = 0, array $errcontext = []) use (&$isCaught): bool {
+        set_error_handler(static function (int $n, string $s, string $f = '', int $l = 0, array $c = [])
+        use (&$isCaught): bool {
             $isCaught = true;
+
             return true;
         });
         $config = ['name' => '*', 'keys' => [['fields' => ['id']]]];
@@ -31,4 +44,36 @@ public function testMethodGetKeyFieldsTriggersDeprecation(): void
 
         restore_error_handler();
     }
+
+    public function getDataForTestMethodGetKeyFields(): \Generator
+    {
+        yield [
+            ['id'],
+            ['name' => '*', 'keyFields' => ['id']],
+        ];
+        yield [
+            ['id', 'email'],
+            ['name' => '*', 'keyFields' => ['id', 'email']],
+        ];
+        yield [
+            ['id'],
+            ['name' => '*', 'keys' => [['fields' => 'id']]],
+        ];
+        yield [
+            ['id'],
+            ['name' => '*', 'keys' => [['fields' => ['id']]]],
+        ];
+        yield [
+            ['id', 'email'],
+            ['name' => '*', 'keys' => [['fields' => ['id', 'email']]]],
+        ];
+        yield [
+            ['id', 'email'],
+            ['name' => '*', 'keys' => [['fields' => ['id']], ['fields' => ['email']]]],
+        ];
+        yield [
+            ['id', 'email'],
+            ['name' => '*', 'keys' => [['fields' => 'id'], ['fields' => 'email']]],
+        ];
+    }
 }
\ No newline at end of file

From 7002d92defa51d1076907315c67ee7b400929c29 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Wed, 7 Sep 2022 21:49:17 +0300
Subject: [PATCH 37/40] Fix test failed assertion message.

---
 test/EntityTest.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/EntityTest.php b/test/EntityTest.php
index e759ff2..1fd308c 100644
--- a/test/EntityTest.php
+++ b/test/EntityTest.php
@@ -40,7 +40,7 @@ public function testMethodGetKeyFieldsTriggersDeprecation(): void
         $config = ['name' => '*', 'keys' => [['fields' => ['id']]]];
         (new EntityObjectType($config))->getKeyFields();
 
-        self::assertTrue($isCaught, 'It does trigger deprecation error. But it should!');
+        self::assertTrue($isCaught, 'It does not trigger deprecation error. But it should!');
 
         restore_error_handler();
     }

From 1b663b5541c0c7df6e7dc6df2a7c835d4dbfed4f Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 28 Oct 2022 00:14:27 +0300
Subject: [PATCH 38/40] Update entity reference resolver validation

---
 src/Types/EntityObjectType.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index f92ac6a..0b979ee 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -137,7 +137,7 @@ public function resolveReference($ref, $context = null, $info = null)
 
     private function validateReferenceResolver(): void
     {
-        Utils::invariant(isset($this->referenceResolver), 'No reference resolver was set in the configuration.');
+        Utils::invariant(\is_callable($this->referenceResolver), 'Invalid reference resolver configuration.');
     }
 
     /**

From 60feec36a149837a27d144d2f95fd43e288ce270 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Fri, 28 Oct 2022 00:14:57 +0300
Subject: [PATCH 39/40] Remove excess class import

---
 src/FederatedSchemaTrait.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index c7e36ec..f2d04ed 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -8,7 +8,6 @@
 use Apollo\Federation\Types\SchemaExtensionType;
 use Apollo\Federation\Utils\FederatedSchemaPrinter;
 use GraphQL\Type\Definition\CustomScalarType;
-use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\ListOfType;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;

From b81878710f0160f96c97ed1f6b8e5ecaa69acd52 Mon Sep 17 00:00:00 2001
From: Anatoliy Melnikau <amelnikov@aristeksystems.com>
Date: Thu, 9 Feb 2023 21:39:48 +0300
Subject: [PATCH 40/40] Downgrade to PHP 7.1

---
 composer.json                        |  3 ++-
 composer.lock                        |  2 +-
 src/Directives.php                   |  2 +-
 src/Directives/LinkDirective.php     |  9 ++++++++-
 src/Enum/DirectiveEnum.php           |  2 +-
 src/FederatedSchemaTrait.php         | 16 +++++++++++-----
 src/Types/EntityObjectType.php       | 11 +++++++----
 src/Utils/FederatedSchemaPrinter.php | 23 ++++++++++++++++++-----
 test/StarWarsData.php                | 18 ++++++++++++------
 test/StarWarsSchema.php              | 23 ++++++++++++++++++-----
 10 files changed, 79 insertions(+), 30 deletions(-)

diff --git a/composer.json b/composer.json
index 99a662c..c01542d 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,8 @@
     "type": "library",
     "license": "MIT",
     "require": {
-        "php": "^7.4||^8.0",
+        "php": "^7.1||^8.0",
+        "ext-json": "*",
         "webonyx/graphql-php": "^0.13.8 || ^14.0"
     },
     "scripts": {
diff --git a/composer.lock b/composer.lock
index 0da2c98..ff1b0f0 100644
--- a/composer.lock
+++ b/composer.lock
@@ -3209,7 +3209,7 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "^7.4||^8.0"
+        "php": "^7.1||^8.0"
     },
     "platform-dev": [],
     "plugin-api-version": "2.3.0"
diff --git a/src/Directives.php b/src/Directives.php
index 08a1b19..db87a81 100644
--- a/src/Directives.php
+++ b/src/Directives.php
@@ -31,7 +31,7 @@ class Directives
      *     shareable: ShareableDirective,
      * }|null
      */
-    private static ?array $directives = null;
+    private static $directives;
 
     /**
      * Gets the @key directive.
diff --git a/src/Directives/LinkDirective.php b/src/Directives/LinkDirective.php
index 87f3c27..93d2c4a 100644
--- a/src/Directives/LinkDirective.php
+++ b/src/Directives/LinkDirective.php
@@ -21,7 +21,14 @@ public function __construct()
     {
         $linkImport = new CustomScalarType([
             'name' => 'link_Import',
-            'serialize' => static fn ($value) => json_encode($value, \JSON_THROW_ON_ERROR),
+            'serialize' => static function ($value) {
+                $data = json_encode($value);
+                if (json_last_error()) {
+                    throw new \RuntimeException(json_last_error_msg());
+                }
+
+                return $data;
+            },
             'parseValue' => static function ($value) {
                 if (\is_string($value)) {
                     return $value;
diff --git a/src/Enum/DirectiveEnum.php b/src/Enum/DirectiveEnum.php
index 06abf9a..30d466a 100644
--- a/src/Enum/DirectiveEnum.php
+++ b/src/Enum/DirectiveEnum.php
@@ -18,7 +18,7 @@ class DirectiveEnum
     /**
      * @var string[]|null
      */
-    protected static ?array $constants = null;
+    protected static $constants;
 
     /**
      * @return string[]
diff --git a/src/FederatedSchemaTrait.php b/src/FederatedSchemaTrait.php
index f2d04ed..b41ce64 100644
--- a/src/FederatedSchemaTrait.php
+++ b/src/FederatedSchemaTrait.php
@@ -20,12 +20,12 @@ trait FederatedSchemaTrait
     /**
      * @var EntityObjectType[]
      */
-    protected array $entityTypes = [];
+    protected $entityTypes = [];
 
     /**
      * @var SchemaExtensionType[]
      */
-    protected array $schemaExtensionTypes = [];
+    protected $schemaExtensionTypes = [];
 
     /**
      * Returns all the resolved entity types in the schema.
@@ -89,7 +89,9 @@ protected function getQueryTypeServiceFieldConfig(): array
             'fields' => [
                 FederatedSchema::RESERVED_FIELD_SDL => [
                     'type' => Type::string(),
-                    'resolve' => fn (): string => FederatedSchemaPrinter::doPrint($this),
+                    'resolve' => function (): string {
+                        return FederatedSchemaPrinter::doPrint($this);
+                    },
                 ],
             ],
         ]);
@@ -97,7 +99,9 @@ protected function getQueryTypeServiceFieldConfig(): array
         return [
             FederatedSchema::RESERVED_FIELD_SERVICE => [
                 'type' => Type::nonNull($serviceType),
-                'resolve' => static fn (): array => [],
+                'resolve' => static function (): array {
+                    return [];
+                },
             ],
         ];
     }
@@ -120,7 +124,9 @@ protected function getQueryTypeEntitiesFieldConfig(?array $config): array
 
         $anyType = new CustomScalarType([
             'name' => FederatedSchema::RESERVED_TYPE_ANY,
-            'serialize' => static fn ($value) => $value,
+            'serialize' => static function ($value) {
+                return $value;
+            },
         ]);
 
         return [
diff --git a/src/Types/EntityObjectType.php b/src/Types/EntityObjectType.php
index 0b979ee..f675f25 100644
--- a/src/Types/EntityObjectType.php
+++ b/src/Types/EntityObjectType.php
@@ -56,7 +56,7 @@ class EntityObjectType extends ObjectType
     /**
      * @var array<int,array{fields: array<int,string>|array<int|string,string|array<int|string,mixed>>, resolvable: bool }>
      */
-    private array $keys;
+    private $keys;
 
     /**
      * @param array<string,mixed> $config
@@ -68,8 +68,9 @@ public function __construct(array $config)
             'Use only one way to define directives @key.'
         );
 
-        $this->keys = $config[self::FIELD_KEYS]
-            ?? array_map(static fn ($x): array => ['fields' => $x], $config['keyFields']);
+        $this->keys = $config[self::FIELD_KEYS] ?? array_map(static function ($x): array {
+            return ['fields' => $x];
+        }, $config['keyFields']);
 
         if (isset($config[self::FIELD_REFERENCE_RESOLVER])) {
             self::validateResolveReference($config);
@@ -97,7 +98,9 @@ public function getKeyFields(): array
             \E_USER_DEPRECATED
         );
 
-        return array_merge(...array_map(static fn(array $x): array => (array) $x['fields'], $this->keys));
+        return array_merge(...array_map(static function (array $x): array {
+            return (array) $x['fields'];
+        }, $this->keys));
     }
 
     /**
diff --git a/src/Utils/FederatedSchemaPrinter.php b/src/Utils/FederatedSchemaPrinter.php
index d541e20..281584d 100644
--- a/src/Utils/FederatedSchemaPrinter.php
+++ b/src/Utils/FederatedSchemaPrinter.php
@@ -73,8 +73,12 @@ public static function doPrint(Schema $schema, array $options = []): string
     {
         return static::printFilteredSchema(
             $schema,
-            static fn (Directive $type): bool => !Directive::isSpecifiedDirective($type) && !static::isFederatedDirective($type),
-            static fn (Type $type): bool => !Type::isBuiltInType($type),
+            static function (Directive $type): bool {
+                return !Directive::isSpecifiedDirective($type) && !static::isFederatedDirective($type);
+            },
+            static function (Type $type): bool {
+                return !Type::isBuiltInType($type);
+            },
             $options
         );
     }
@@ -185,7 +189,9 @@ protected static function printImplementedInterfaces(ObjectType $type): string
         $interfaces = $type->getInterfaces();
 
         return !empty($interfaces)
-            ? ' implements ' . implode(' & ', array_map(static fn (InterfaceType $i): string => $i->name, $interfaces))
+            ? ' implements ' . implode(' & ', array_map(static function (InterfaceType $i): string {
+                return $i->name;
+            }, $interfaces))
             : '';
     }
 
@@ -257,7 +263,12 @@ protected static function printLinkDirectiveArgumentValue($argument, string $nam
             throw new \InvalidArgumentException('Invalid type of "import" argument value');
         }
 
-        return json_encode($argument, \JSON_THROW_ON_ERROR);
+        $data = json_encode($argument);
+        if (json_last_error()) {
+            throw new \RuntimeException(json_last_error_msg());
+        }
+
+        return $data;
     }
 
     /**
@@ -301,7 +312,9 @@ protected static function printSchemaExtensionType(SchemaExtensionType $schemaEx
 
         return sprintf(
             'extend schema %s\n',
-            implode("\n", array_map(static fn (array $x): string => static::printLinkDirectiveConfig($x), $links)),
+            implode("\n", array_map(static function (array $x): string {
+                return static::printLinkDirectiveConfig($x);
+            }, $links))
         );
     }
 }
diff --git a/test/StarWarsData.php b/test/StarWarsData.php
index 27bd28e..b2b9098 100644
--- a/test/StarWarsData.php
+++ b/test/StarWarsData.php
@@ -9,24 +9,26 @@ class StarWarsData
     /**
      * @var array<int,array<string,mixed>>|null
      */
-    private static ?array $episodes = null;
+    private static $episodes;
 
     /**
      * @var array<int,array<string,mixed>>|null
      */
-    private static ?array $characters = null;
+    private static $characters;
 
     /**
      * @var array<int,array<string,mixed>>|null
      */
-    private static ?array $locations = null;
+    private static $locations;
 
     /**
      * @return array<string,mixed>|null
      */
     public static function getEpisodeById(int $id): ?array
     {
-        $matches = array_filter(self::getEpisodes(), static fn (array $episode): bool => $episode['id'] === $id);
+        $matches = array_filter(self::getEpisodes(), static function (array $episode) use ($id): bool {
+            return $episode['id'] === $id;
+        });
 
         return reset($matches) ?: null;
     }
@@ -66,7 +68,9 @@ public static function getEpisodes(): array
      */
     public static function getCharactersByIds(array $ids): array
     {
-        return array_filter(self::getCharacters(), static fn ($item): bool => \in_array($item['id'], $ids, true));
+        return array_filter(self::getCharacters(), static function ($item) use ($ids): bool {
+            return \in_array($item['id'], $ids, true);
+        });
     }
 
     /**
@@ -104,7 +108,9 @@ public static function getCharacters(): array
      */
     public static function getLocationsByIds(array $ids): array
     {
-        return array_filter(self::getLocations(), static fn ($item): bool => \in_array($item['id'], $ids, true));
+        return array_filter(self::getLocations(), static function ($item) use ($ids): bool {
+            return \in_array($item['id'], $ids, true);
+        });
     }
 
     /**
diff --git a/test/StarWarsSchema.php b/test/StarWarsSchema.php
index f04e48f..bec8a2b 100644
--- a/test/StarWarsSchema.php
+++ b/test/StarWarsSchema.php
@@ -15,8 +15,15 @@
 
 class StarWarsSchema
 {
-    public static ?FederatedSchema $episodesSchema = null;
-    public static ?FederatedSchema $overriddenEpisodesSchema = null;
+    /**
+     * @var FederatedSchema|null
+     */
+    public static $episodesSchema;
+
+    /**
+     * @var FederatedSchema|null
+     */
+    public static $overriddenEpisodesSchema;
 
     public static function getEpisodesSchema(): FederatedSchema
     {
@@ -64,7 +71,9 @@ private static function getQueryType(): ObjectType
             'fields' => [
                 'episodes' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull($episodeType))),
-                    'resolve' => static fn (): array => StarWarsData::getEpisodes(),
+                    'resolve' => static function (): array {
+                        return StarWarsData::getEpisodes();
+                    },
                 ],
                 'deprecatedEpisodes' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull($episodeType))),
@@ -88,7 +97,9 @@ private static function getEpisodeType(): EntityObjectType
                 ],
                 'characters' => [
                     'type' => Type::nonNull(Type::listOf(Type::nonNull(self::getCharacterType()))),
-                    'resolve' => static fn ($root): array => StarWarsData::getCharactersByIds($root['characters']),
+                    'resolve' => static function ($root): array {
+                        return StarWarsData::getCharactersByIds($root['characters']);
+                    },
                     'provides' => 'name',
                 ],
             ],
@@ -118,7 +129,9 @@ private static function getCharacterType(): EntityRefObjectType
                 ],
                 'locations' => [
                     'type' => Type::nonNull(Type::listOf(self::getLocationType())),
-                    'resolve' => static fn ($root): array => StarWarsData::getLocationsByIds($root['locations']),
+                    'resolve' => static function ($root): array {
+                        return StarWarsData::getLocationsByIds($root['locations']);
+                    },
                     'requires' => 'name',
                 ],
             ],