feat: adjust TS2691 message for .ts import sources

src/compiler/checker.ts

@@ -3309,7 +3309,17 @@ namespace ts {
                     const tsExtension = tryExtractTSExtension(moduleReference);
                     if (tsExtension) {
                         const diag = Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
-                        error(errorNode, diag, tsExtension, removeExtension(moduleReference, tsExtension));
+                        const importSourceWithoutExtension = removeExtension(moduleReference, tsExtension);
+                        let replacedImportSource = importSourceWithoutExtension;
+                        /**
+                         * Direct users to import source with .js extension if outputting an ES module.
+                         * @see https://github.com/microsoft/TypeScript/issues/42151
+                         */
+                        const moduleKind = getEmitModuleKind(compilerOptions);
+                        if (moduleKind >= ModuleKind.ES2015) {
+                            replacedImportSource += ".js";
+                        }
+                        error(errorNode, diag, tsExtension, replacedImportSource);
                     }
                     else if (!compilerOptions.resolveJsonModule &&
                         fileExtensionIs(moduleReference, Extension.Json) &&

tests/baselines/reference/moduleResolutionNoTsCJS.errors.txt

@@ -0,0 +1,33 @@
+tests/cases/compiler/user.ts(1,15): error TS2691: An import path cannot end with a '.ts' extension. Consider importing './x' instead.
+tests/cases/compiler/user.ts(2,15): error TS2691: An import path cannot end with a '.tsx' extension. Consider importing './y' instead.
+tests/cases/compiler/user.ts(3,15): error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './z' instead.
+
+
+==== tests/cases/compiler/x.ts (0 errors) ====
+    // CommonJS output
+
+    export default 0;
+
+==== tests/cases/compiler/y.tsx (0 errors) ====
+    export default 0;
+
+==== tests/cases/compiler/z.d.ts (0 errors) ====
+    declare const x: number;
+    export default x;
+
+==== tests/cases/compiler/user.ts (3 errors) ====
+    import x from "./x.ts";
+                  ~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.ts' extension. Consider importing './x' instead.
+    import y from "./y.tsx";
+                  ~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.tsx' extension. Consider importing './y' instead.
+    import z from "./z.d.ts";
+                  ~~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './z' instead.
+
+    // Making sure the suggested fixes are valid:
+    import x2 from "./x";
+    import y2 from "./y";
+    import z2 from "./z";
+

tests/baselines/reference/moduleResolutionNoTsCJS.js

@@ -0,0 +1,37 @@
+//// [tests/cases/compiler/moduleResolutionNoTsCJS.ts] ////
+
+//// [x.ts]
+// CommonJS output
+
+export default 0;
+
+//// [y.tsx]
+export default 0;
+
+//// [z.d.ts]
+declare const x: number;
+export default x;
+
+//// [user.ts]
+import x from "./x.ts";
+import y from "./y.tsx";
+import z from "./z.d.ts";
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+import y2 from "./y";
+import z2 from "./z";
+
+
+//// [x.js]
+"use strict";
+// CommonJS output
+exports.__esModule = true;
+exports["default"] = 0;
+//// [y.jsx]
+"use strict";
+exports.__esModule = true;
+exports["default"] = 0;
+//// [user.js]
+"use strict";
+exports.__esModule = true;

tests/baselines/reference/moduleResolutionNoTsCJS.symbols

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/x.ts ===
+// CommonJS output
+No type information for this code.
+No type information for this code.export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/y.tsx ===
+export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/z.d.ts ===
+declare const x: number;
+>x : Symbol(x, Decl(z.d.ts, 0, 13))
+
+export default x;
+>x : Symbol(x, Decl(z.d.ts, 0, 13))
+
+=== tests/cases/compiler/user.ts ===
+import x from "./x.ts";
+>x : Symbol(x, Decl(user.ts, 0, 6))
+
+import y from "./y.tsx";
+>y : Symbol(y, Decl(user.ts, 1, 6))
+
+import z from "./z.d.ts";
+>z : Symbol(z, Decl(user.ts, 2, 6))
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+>x2 : Symbol(x2, Decl(user.ts, 5, 6))
+
+import y2 from "./y";
+>y2 : Symbol(y2, Decl(user.ts, 6, 6))
+
+import z2 from "./z";
+>z2 : Symbol(z2, Decl(user.ts, 7, 6))
+

tests/baselines/reference/moduleResolutionNoTsCJS.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/x.ts ===
+// CommonJS output
+No type information for this code.
+No type information for this code.export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/y.tsx ===
+export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/z.d.ts ===
+declare const x: number;
+>x : number
+
+export default x;
+>x : number
+
+=== tests/cases/compiler/user.ts ===
+import x from "./x.ts";
+>x : any
+
+import y from "./y.tsx";
+>y : any
+
+import z from "./z.d.ts";
+>z : any
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+>x2 : 0
+
+import y2 from "./y";
+>y2 : 0
+
+import z2 from "./z";
+>z2 : number
+

tests/baselines/reference/moduleResolutionNoTsESM.errors.txt

@@ -0,0 +1,33 @@
+tests/cases/compiler/user.ts(1,15): error TS2691: An import path cannot end with a '.ts' extension. Consider importing './x.js' instead.
+tests/cases/compiler/user.ts(2,15): error TS2691: An import path cannot end with a '.tsx' extension. Consider importing './y.js' instead.
+tests/cases/compiler/user.ts(3,15): error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './z.js' instead.
+
+
+==== tests/cases/compiler/x.ts (0 errors) ====
+    // ESM output
+
+    export default 0;
+
+==== tests/cases/compiler/y.tsx (0 errors) ====
+    export default 0;
+
+==== tests/cases/compiler/z.d.ts (0 errors) ====
+    declare const x: number;
+    export default x;
+
+==== tests/cases/compiler/user.ts (3 errors) ====
+    import x from "./x.ts";
+                  ~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.ts' extension. Consider importing './x.js' instead.
+    import y from "./y.tsx";
+                  ~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.tsx' extension. Consider importing './y.js' instead.
+    import z from "./z.d.ts";
+                  ~~~~~~~~~~
+!!! error TS2691: An import path cannot end with a '.d.ts' extension. Consider importing './z.js' instead.
+
+    // Making sure the suggested fixes are valid:
+    import x2 from "./x";
+    import y2 from "./y";
+    import z2 from "./z";
+

tests/baselines/reference/moduleResolutionNoTsESM.js

@@ -0,0 +1,32 @@
+//// [tests/cases/compiler/moduleResolutionNoTsESM.ts] ////
+
+//// [x.ts]
+// ESM output
+
+export default 0;
+
+//// [y.tsx]
+export default 0;
+
+//// [z.d.ts]
+declare const x: number;
+export default x;
+
+//// [user.ts]
+import x from "./x.ts";
+import y from "./y.tsx";
+import z from "./z.d.ts";
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+import y2 from "./y";
+import z2 from "./z";
+
+
+//// [x.js]
+// ESM output
+export default 0;
+//// [y.jsx]
+export default 0;
+//// [user.js]
+export {};

tests/baselines/reference/moduleResolutionNoTsESM.symbols

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/x.ts ===
+// ESM output
+No type information for this code.
+No type information for this code.export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/y.tsx ===
+export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/z.d.ts ===
+declare const x: number;
+>x : Symbol(x, Decl(z.d.ts, 0, 13))
+
+export default x;
+>x : Symbol(x, Decl(z.d.ts, 0, 13))
+
+=== tests/cases/compiler/user.ts ===
+import x from "./x.ts";
+>x : Symbol(x, Decl(user.ts, 0, 6))
+
+import y from "./y.tsx";
+>y : Symbol(y, Decl(user.ts, 1, 6))
+
+import z from "./z.d.ts";
+>z : Symbol(z, Decl(user.ts, 2, 6))
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+>x2 : Symbol(x2, Decl(user.ts, 5, 6))
+
+import y2 from "./y";
+>y2 : Symbol(y2, Decl(user.ts, 6, 6))
+
+import z2 from "./z";
+>z2 : Symbol(z2, Decl(user.ts, 7, 6))
+

tests/baselines/reference/moduleResolutionNoTsESM.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/x.ts ===
+// ESM output
+No type information for this code.
+No type information for this code.export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/y.tsx ===
+export default 0;
+No type information for this code.
+No type information for this code.=== tests/cases/compiler/z.d.ts ===
+declare const x: number;
+>x : number
+
+export default x;
+>x : number
+
+=== tests/cases/compiler/user.ts ===
+import x from "./x.ts";
+>x : any
+
+import y from "./y.tsx";
+>y : any
+
+import z from "./z.d.ts";
+>z : any
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+>x2 : 0
+
+import y2 from "./y";
+>y2 : 0
+
+import z2 from "./z";
+>z2 : number
+

tests/cases/compiler/moduleResolutionNoTsCJS.ts

@@ -0,0 +1,23 @@
+// CommonJS output
+// @module: commonjs
+
+// @jsx: Preserve
+// @filename: x.ts
+export default 0;
+
+// @filename: y.tsx
+export default 0;
+
+// @filename: z.d.ts
+declare const x: number;
+export default x;
+
+// @filename: user.ts
+import x from "./x.ts";
+import y from "./y.tsx";
+import z from "./z.d.ts";
+
+// Making sure the suggested fixes are valid:
+import x2 from "./x";
+import y2 from "./y";
+import z2 from "./z";

tests/cases/compiler/moduleResolutionNoTs.ts → tests/cases/compiler/moduleResolutionNoTsESM.ts

@@ -1,3 +1,6 @@
+// ESM output
+// @module: es2015
+
 // @jsx: Preserve
 // @filename: x.ts
 export default 0;