symfony
diff --git a/‎UPGRADE-4.3.md
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diff --git a/‎UPGRADE-5.0.md
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diff --git a/‎src/Symfony/Component/Form/ButtonBuilder.php
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diff --git a/‎src/Symfony/Component/Form/CHANGELOG.md
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diff --git a/‎src/Symfony/Component/Form/Tests/ButtonBuilderTest.php
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+8-1Lines changed: 8 additions & 1 deletion b/‎src/Symfony/Component/Form/Tests/ButtonBuilderTest.php
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+8-1Lines changed: 8 additions & 1 deletion
@@ -5,3 +5,12 @@ Config
 ------
 
  * Deprecated using environment variables with `cannotBeEmpty()` if the value is validated with `validate()`
+
+Form
+----
+
+ * Using names for buttons that do not start with a letter, a digit, or an underscore is deprecated and will lead to an
+   exception in 5.0.
+
+ * Using names for buttons that do not contain only letters, digits, underscores, hyphens, and colons is deprecated and
+   will lead to an exception in 5.0.
@@ -73,6 +73,11 @@ Finder
 Form
 ----
 
+ * Using names for buttons that do not start with a letter, a digit, or an underscore leads to an exception.
+
+ * Using names for buttons that do not contain only letters, digits, underscores, hyphens, and colons leads to an
+   exception.
+
  * The `getExtendedType()` method was removed from the `FormTypeExtensionInterface`. It is replaced by the the static
    `getExtendedTypes()` method which must return an iterable of extended types.
 
 
@@ -63,6 +63,18 @@ public function __construct(?string $name, array $options = array())
 
         $this->name = $name;
         $this->options = $options;
+
+        if (\preg_match('/^([^a-z0-9_].*)?(.*[^a-zA-Z0-9_\-:].*)?$/D', $name, $matches)) {
+            if (isset($matches[1])) {
+                @trigger_error(sprintf('Using names for buttons that do not start with a letter, a digit, or an underscore is deprecated since Symfony 4.3 and will throw an exception in 5.0 ("%s" given).', $name), E_USER_DEPRECATED);
+            }
+            if (isset($matches[2])) {
+                @trigger_error(sprintf('Using names for buttons that do not contain only letters, digits, underscores ("_"), hyphens ("-") and colons (":") ("%s" given) is deprecated since Symfony 4.3 and will throw an exception in 5.0.', $name), E_USER_DEPRECATED);
+            }
+        }
+
+        // to be added in 5.0
+        // FormConfigBuilder::validateName($name);
     }
 
     /**
 
@@ -4,6 +4,10 @@ CHANGELOG
 4.3.0
 -----
 
+ * Using names for buttons that do not start with a letter, a digit, or an underscore is deprecated and will lead to an
+   exception in 5.0.
+ * Using names for buttons that do not contain only letters, digits, underscores, hyphens, and colons is deprecated and
+   will lead to an exception in 5.0.
  * added `block_prefix` option to `BaseType`.
 
 4.2.0
 
@@ -28,7 +28,6 @@ public function getValidNames()
             array('foo'),
             array('0'),
             array(0),
-            array('button[]'),
         );
     }
 
@@ -40,6 +39,14 @@ public function testValidNames($name)
         $this->assertInstanceOf('\Symfony\Component\Form\ButtonBuilder', new ButtonBuilder($name));
     }
 
+    /**
+     * @group legacy
+     */
+    public function testNameContainingIllegalCharacters()
+    {
+        $this->assertInstanceOf('\Symfony\Component\Form\ButtonBuilder', new ButtonBuilder('button[]'));
+    }
+
     public function getInvalidNames()
     {
         return array(