feat(node-resolve): Resolve js/jsx/mjs/cjs imports from TypeScript files

packages/node-resolve/src/index.js

@@ -146,11 +146,18 @@ export function nodeResolve(opts = {}) {
       importSpecifierList.push(`./${importee}`);
     }
 
-    // TypeScript files may import '.js' to refer to either '.ts' or '.tsx'
-    if (importer && importee.endsWith('.js')) {
-      for (const ext of ['.ts', '.tsx']) {
-        if (importer.endsWith(ext) && extensions.includes(ext)) {
-          importSpecifierList.push(importee.replace(/.js$/, ext));
+    // TypeScript files may import '.mjs' or '.cjs' to refer to either '.mts' or '.cts'.
+    // They may also import .js to refer to either .ts or .tsx, and .jsx to refer to .tsx.
+    if (importer && /\.(ts|mts|cts|tsx)$/.test(importer)) {
+      for (const [importeeExt, resolvedExt] of [
+        ['.js', '.ts'],
+        ['.js', '.tsx'],
+        ['.jsx', '.tsx'],
+        ['.mjs', '.mts'],
+        ['.cjs', '.cts']
+      ]) {
+        if (importee.endsWith(importeeExt) && extensions.includes(resolvedExt)) {
+          importSpecifierList.push(importee.slice(0, -importeeExt.length) + resolvedExt);
         }
       }
     }

packages/node-resolve/test/fixtures/ts-import-cjs-extension/import-ts-with-cjs-extension.ts

@@ -0,0 +1,4 @@
+import { main } from './main.cjs';
+// This resolves as main.cts and _not_ main.cjs, despite the extension
+const mainResult = main();
+export default mainResult;

packages/node-resolve/test/fixtures/ts-import-cjs-extension/main.cts

@@ -0,0 +1,11 @@
+// To make this very clearly TypeScript and not just CJS with a CTS extension
+type TestType = string | string[];
+interface Main {
+  (): string;
+  propertyCall(input?: TestType): TestType;
+}
+
+const main: Main = () => 'It works!';
+main.propertyCall = () => '';
+
+export { main };

packages/node-resolve/test/fixtures/ts-import-mjs-extension/import-ts-with-mjs-extension.ts

@@ -0,0 +1,4 @@
+import { main } from './main.mjs';
+// This resolves as main.mts and _not_ main.mjs, despite the extension
+const mainResult = main();
+export default mainResult;

packages/node-resolve/test/fixtures/ts-import-mjs-extension/main.mts

@@ -0,0 +1,11 @@
+// To make this very clearly TypeScript and not just MJS with a MTS extension
+type TestType = string | string[];
+interface Main {
+  (): string;
+  propertyCall(input?: TestType): TestType;
+}
+
+const main: Main = () => 'It works!';
+main.propertyCall = () => '';
+
+export { main };

packages/node-resolve/test/fixtures/tsx-import-js-extension/MyComponent.tsx

@@ -0,0 +1,7 @@
+// To make this very clearly TypeScript and not just JS with a TS extension
+type TestType = string | string[];
+function MyComponent() {
+  return 'It works!';
+}
+
+export { MyComponent };

packages/node-resolve/test/fixtures/tsx-import-js-extension/import-tsx-with-js-extension.ts

@@ -0,0 +1,4 @@
+import { MyComponent } from './MyComponent.js';
+// This resolves as MyComponent.tsx and _not_ MyComponent.js, despite the extension
+const componentResult = MyComponent();
+export default componentResult;

packages/node-resolve/test/fixtures/tsx-import-jsx-extension/MyComponent.tsx

@@ -0,0 +1,7 @@
+// To make this very clearly TypeScript and not just JS with a TS extension
+type TestType = string | string[];
+function MyComponent() {
+  return 'It works!';
+}
+
+export { MyComponent };

packages/node-resolve/test/fixtures/tsx-import-jsx-extension/import-tsx-with-jsx-extension.ts

@@ -0,0 +1,4 @@
+import { MyComponent } from './MyComponent.jsx';
+// This resolves as MyComponent.tsx and _not_ MyComponent.jsx, despite the extension
+const componentResult = MyComponent();
+export default componentResult;

packages/node-resolve/test/test.mjs

@@ -168,6 +168,82 @@ test('supports JS extensions in TS when referring to TS imports', async (t) => {
   t.is(module.exports, 'It works!');
 });
 
+test('supports JS extensions in TS when referring to TSX imports', async (t) => {
+  const bundle = await rollup({
+    input: 'tsx-import-js-extension/import-tsx-with-js-extension.ts',
+    onwarn: failOnWarn(t),
+    plugins: [
+      nodeResolve({
+        extensions: ['.js', '.ts', '.tsx']
+      }),
+      babel({
+        babelHelpers: 'bundled',
+        plugins: ['@babel/plugin-transform-typescript'],
+        extensions: ['.js', '.ts', '.tsx']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+  t.is(module.exports, 'It works!');
+});
+
+test('supports JSX extensions in TS when referring to TSX imports', async (t) => {
+  const bundle = await rollup({
+    input: 'tsx-import-jsx-extension/import-tsx-with-jsx-extension.ts',
+    onwarn: failOnWarn(t),
+    plugins: [
+      nodeResolve({
+        extensions: ['.js', '.ts', '.tsx']
+      }),
+      babel({
+        babelHelpers: 'bundled',
+        plugins: ['@babel/plugin-transform-typescript'],
+        extensions: ['.js', '.ts', '.tsx']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+  t.is(module.exports, 'It works!');
+});
+
+test('supports MJS extensions in TS when referring to MTS imports', async (t) => {
+  const bundle = await rollup({
+    input: 'ts-import-mjs-extension/import-ts-with-mjs-extension.ts',
+    onwarn: failOnWarn(t),
+    plugins: [
+      nodeResolve({
+        extensions: ['.js', '.ts', '.mjs', '.mts']
+      }),
+      babel({
+        babelHelpers: 'bundled',
+        plugins: ['@babel/plugin-transform-typescript'],
+        extensions: ['.js', '.ts', '.mjs', '.mts']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+  t.is(module.exports, 'It works!');
+});
+
+test('supports CJS extensions in TS when referring to CTS imports', async (t) => {
+  const bundle = await rollup({
+    input: 'ts-import-cjs-extension/import-ts-with-cjs-extension.ts',
+    onwarn: failOnWarn(t),
+    plugins: [
+      nodeResolve({
+        extensions: ['.js', '.ts', '.cjs', '.cts']
+      }),
+      babel({
+        babelHelpers: 'bundled',
+        plugins: ['@babel/plugin-transform-typescript'],
+        extensions: ['.js', '.ts', '.cjs', '.cts']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+  t.is(module.exports, 'It works!');
+});
+
 test('supports JS extensions in TS actually importing JS with export map', async (t) => {
   const bundle = await rollup({
     input: 'ts-import-js-extension-for-js-file-export-map/import-js-with-js-extension.ts',