Add explicit flag for importing from .ts extensions

microsoft · andrewbranch · Dec 13, 2022 · Jul 28, 2022 · Jul 29, 2022 · Jul 29, 2022
commit af03675a085d6b799b8b7ce7e8f6f4baf4008ea9
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -3620,9 +3620,9 @@ namespace ts {
                            getSuggestedImportSource(Debug.checkDefined(tryExtractTSExtension(moduleReference))));
                    }
                }
-                else if (resolvedModule.resolvedUsingTsExtension && !shouldAllowTsExtension(compilerOptions)) {
+                else if (resolvedModule.resolvedUsingTsExtension && !shouldAllowImportingTsExtension(compilerOptions, currentSourceFile.fileName)) {
                    const tsExtension = Debug.checkDefined(tryExtractTSExtension(moduleReference));
-                    errorOnTSExtensionImport(tsExtension);
+                    error(errorNode, Diagnostics.An_import_path_can_only_end_with_a_0_extension_when_allowImportingTsExtensions_is_enabled, tsExtension);
                }

                if (sourceFile.symbol) {

diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
@@ -956,6 +956,14 @@ namespace ts {
            category: Diagnostics.Modules,
            description: Diagnostics.List_of_file_name_suffixes_to_search_when_resolving_a_module,
        },
+        {
+            name: "allowImportingTsExtensions",
+            type: "boolean",
+            affectsModuleResolution: true,
+            category: Diagnostics.Modules,
+            description: Diagnostics.Allow_imports_to_include_TypeScript_file_extensions_Requires_moduleResolution_minimal_and_either_noEmit_or_emitDeclarationOnly_to_be_set,
+            defaultValueDescription: false,
+        },

        // Source Maps
        {

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -4229,6 +4229,14 @@
        "category": "Error",
        "code": 5095
    },
+    "Option 'allowImportingTsExtensions' can only be used when 'moduleResolution' is set to 'minimal' and either 'noEmit' or 'emitDeclarationOnly' is set.": {
+        "category": "Error",
+        "code": 5096
+    },
+    "An import path can only end with a '{0}' extension when 'allowImportingTsExtensions' is enabled.": {
+        "category": "Error",
+        "code": 5097
+    },

    "Generates a sourcemap for each corresponding '.d.ts' file.": {
        "category": "Message",
@@ -4451,10 +4459,6 @@
        "category": "Message",
        "code": 6066
    },
-    "Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6).": {
-        "category": "Message",
-        "code": 6069
-    },
    "Initializes a TypeScript project and creates a tsconfig.json file.": {
        "category": "Message",
        "code": 6070
@@ -5418,6 +5422,10 @@
        "category": "Message",
        "code": 6401
    },
+    "Allow imports to include TypeScript file extensions. Requires '--moduleResolution minimal' and either '--noEmit' or '--emitDeclarationOnly' to be set.": {
+        "category": "Message",
+        "code": 6402
+    },

    "The expected type comes from property '{0}' which is declared here on type '{1}'": {
        "category": "Message",

diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
@@ -2716,8 +2716,12 @@ namespace ts {
      return getEmitModuleResolutionKind(compilerOptions) === ModuleResolutionKind.Minimal;
    }

-    export function shouldAllowTsExtension(compilerOptions: CompilerOptions) {
-        return shouldResolveTsExtension(compilerOptions) && !!compilerOptions.noEmit;
+    // Program errors validate that `noEmit` or `emitDeclarationOnly` is also set,
+    // so this function doesn't check them to avoid propagating errors.
+    export function shouldAllowImportingTsExtension(compilerOptions: CompilerOptions, fromFileName?: string) {
+        return shouldResolveTsExtension(compilerOptions) && (
+            !!compilerOptions.allowImportingTsExtensions ||
+            fromFileName && isDeclarationFileName(fromFileName));
    }

    /**

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
@@ -3657,6 +3657,10 @@ namespace ts {
                createOptionValueDiagnostic("importsNotUsedAsValues", Diagnostics.Option_preserveValueImports_can_only_be_used_when_module_is_set_to_es2015_or_later);
            }

+            if (options.allowImportingTsExtensions && !(getEmitModuleResolutionKind(options) === ModuleResolutionKind.Minimal && (options.noEmit || options.emitDeclarationOnly))) {
+                createOptionValueDiagnostic("allowImportingTsExtensions", Diagnostics.Option_allowImportingTsExtensions_can_only_be_used_when_moduleResolution_is_set_to_minimal_and_either_noEmit_or_emitDeclarationOnly_is_set);
+            }
+
            // If the emit is enabled make sure that every output file is unique and not overwriting any of the input files
            if (!options.noEmit && !options.suppressOutputPathCheck) {
                const emitHost = getEmitHost();

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -6543,6 +6543,7 @@ namespace ts {

    export interface CompilerOptions {
        /*@internal*/ all?: boolean;
+        allowImportingTsExtensions?: boolean;
        allowJs?: boolean;
        /*@internal*/ allowNonTsExtensions?: boolean;
        allowSyntheticDefaultImports?: boolean;

diff --git a/src/testRunner/compilerRunner.ts b/src/testRunner/compilerRunner.ts
@@ -119,6 +119,7 @@ namespace Harness {
            "module",
            "moduleResolution",
            "moduleDetection",
+            "allowImportingTsExtensions",
            "target",
            "jsx",
            "noEmit",

diff --git a/tests/baselines/reference/minimal_pathsAndBaseUrl.errors.txt b/tests/baselines/reference/minimal_pathsAndBaseUrl.errors.txt
@@ -6,6 +6,7 @@
      "compilerOptions": {
        "moduleResolution": "minimal",
        "noEmit": true,
+        "allowImportingTsExtensions": true,
        "baseUrl": ".",
        "paths": {
          "*": [

diff --git a/...ines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).errors.txt b/...ines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).errors.txt
@@ -0,0 +1,107 @@
+error TS5056: Cannot write file 'dist/c.js' because it would be overwritten by multiple input files.
+error TS6231: Could not resolve the path '/project/e' with the extensions: '.ts', '.tsx', '.d.ts', '.cts', '.d.cts', '.mts', '.d.mts'.
+  The file is in the program because:
+    Root file specified for compilation
+error TS6504: File '/project/b.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+  The file is in the program because:
+    Root file specified for compilation
+/project/main.ts(1,16): error TS2307: Cannot find module './a' or its corresponding type declarations.
+/project/main.ts(3,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+/project/main.ts(5,16): error TS2307: Cannot find module './b' or its corresponding type declarations.
+/project/main.ts(7,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+/project/main.ts(8,16): error TS2845: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b.js' instead?
+/project/main.ts(11,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+/project/main.ts(12,16): error TS5097: An import path can only end with a '.tsx' extension when 'allowImportingTsExtensions' is enabled.
+/project/main.ts(12,16): error TS6142: Module './c.tsx' was resolved to '/project/c.tsx', but '--jsx' is not set.
+/project/main.ts(14,16): error TS2307: Cannot find module './d' or its corresponding type declarations.
+/project/main.ts(15,16): error TS2307: Cannot find module './d/index' or its corresponding type declarations.
+/project/main.ts(16,16): error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+/project/main.ts(18,16): error TS2307: Cannot find module './e' or its corresponding type declarations.
+/project/types.d.ts(2,16): error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './a.js' instead.
+/project/types.d.ts(3,21): error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './a.js' instead.
+
+
+!!! error TS5056: Cannot write file 'dist/c.js' because it would be overwritten by multiple input files.
+!!! error TS6231: Could not resolve the path '/project/e' with the extensions: '.ts', '.tsx', '.d.ts', '.cts', '.d.cts', '.mts', '.d.mts'.
+!!! error TS6231:   The file is in the program because:
+!!! error TS6231:     Root file specified for compilation
+!!! error TS6504: File '/project/b.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
+!!! error TS6504:   The file is in the program because:
+!!! error TS6504:     Root file specified for compilation
+==== /project/a.ts (0 errors) ====
+    export {};
+
+==== /project/b.ts (0 errors) ====
+    export {};
+
+==== /project/b.js (0 errors) ====
+    export {};
+
+==== /project/b.d.ts (0 errors) ====
+    export {};
+
+==== /project/c.ts (0 errors) ====
+    export {};
+
+==== /project/c.tsx (0 errors) ====
+    export {};
+
+==== /project/d/index.ts (0 errors) ====
+    export {};
+
+==== /project/e (0 errors) ====
+    export {};
+
+==== /project/main.ts (12 errors) ====
+    import {} from "./a";
+                   ~~~~~
+!!! error TS2307: Cannot find module './a' or its corresponding type declarations.
+    import {} from "./a.js";
+    import {} from "./a.ts";
+                   ~~~~~~~~
+!!! error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+
+    import {} from "./b";
+                   ~~~~~
+!!! error TS2307: Cannot find module './b' or its corresponding type declarations.
+    import {} from "./b.js";
+    import {} from "./b.ts";
+                   ~~~~~~~~
+!!! error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+    import {} from "./b.d.ts";
+                   ~~~~~~~~~~
+!!! error TS2845: A declaration file cannot be imported without 'import type'. Did you mean to import an implementation file './b.js' instead?
+    import type {} from "./b.d.ts";
+
+    import {} from "./c.ts";
+                   ~~~~~~~~
+!!! error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+    import {} from "./c.tsx";
+                   ~~~~~~~~~
+!!! error TS5097: An import path can only end with a '.tsx' extension when 'allowImportingTsExtensions' is enabled.
+                   ~~~~~~~~~
+!!! error TS6142: Module './c.tsx' was resolved to '/project/c.tsx', but '--jsx' is not set.
+
+    import {} from "./d";
+                   ~~~~~
+!!! error TS2307: Cannot find module './d' or its corresponding type declarations.
+    import {} from "./d/index";
+                   ~~~~~~~~~~~
+!!! error TS2307: Cannot find module './d/index' or its corresponding type declarations.
+    import {} from "./d/index.ts";
+                   ~~~~~~~~~~~~~~
+!!! error TS5097: An import path can only end with a '.ts' extension when 'allowImportingTsExtensions' is enabled.
+
+    import {} from "./e";
+                   ~~~~~
+!!! error TS2307: Cannot find module './e' or its corresponding type declarations.
+
+==== /project/types.d.ts (2 errors) ====
+    import {} from "./a.ts";
+    import {} from "./a.d.ts";
+                   ~~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './a.js' instead.
+    import type {} from "./a.d.ts";
+                        ~~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './a.js' instead.
+
diff --git a/tests/baselines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).js b/tests/baselines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).js
@@ -0,0 +1,64 @@
+//// [tests/cases/conformance/moduleResolution/minimal_relative.ts] ////
+
+//// [a.ts]
+export {};
+
+//// [b.ts]
+export {};
+
+//// [b.js]
+export {};
+
+//// [b.d.ts]
+export {};
+
+//// [c.ts]
+export {};
+
+//// [c.tsx]
+export {};
+
+//// [index.ts]
+export {};
+
+//// [e]
+export {};
+
+//// [main.ts]
+import {} from "./a";
+import {} from "./a.js";
+import {} from "./a.ts";
+
+import {} from "./b";
+import {} from "./b.js";
+import {} from "./b.ts";
+import {} from "./b.d.ts";
+import type {} from "./b.d.ts";
+
+import {} from "./c.ts";
+import {} from "./c.tsx";
+
+import {} from "./d";
+import {} from "./d/index";
+import {} from "./d/index.ts";
+
+import {} from "./e";
+
+//// [types.d.ts]
+import {} from "./a.ts";
+import {} from "./a.d.ts";
+import type {} from "./a.d.ts";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
+//// [b.js]
+"use strict";
+exports.__esModule = true;
+//// [index.js]
+"use strict";
+exports.__esModule = true;
+//// [main.js]
+"use strict";
+exports.__esModule = true;
diff --git a/...selines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).symbols b/...selines/reference/minimal_relative(allowimportingtsextensions=false,noemit=false).symbols
@@ -0,0 +1,44 @@
+=== /project/a.ts ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/b.ts ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/b.d.ts ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/c.ts ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/c.tsx ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/d/index.ts ===
+export {};
+No type information for this code.
+No type information for this code.=== /project/main.ts ===
+import {} from "./a";
+No type information for this code.import {} from "./a.js";
+No type information for this code.import {} from "./a.ts";
+No type information for this code.
+No type information for this code.import {} from "./b";
+No type information for this code.import {} from "./b.js";
+No type information for this code.import {} from "./b.ts";
+No type information for this code.import {} from "./b.d.ts";
+No type information for this code.import type {} from "./b.d.ts";
+No type information for this code.
+No type information for this code.import {} from "./c.ts";
+No type information for this code.import {} from "./c.tsx";
+No type information for this code.
+No type information for this code.import {} from "./d";
+No type information for this code.import {} from "./d/index";
+No type information for this code.import {} from "./d/index.ts";
+No type information for this code.
+No type information for this code.import {} from "./e";
+No type information for this code.
+No type information for this code.=== /project/types.d.ts ===
+import {} from "./a.ts";
+No type information for this code.import {} from "./a.d.ts";
+No type information for this code.import type {} from "./a.d.ts";
+No type information for this code.
+No type information for this code.