feat: support importing CommonJS from ESM files

CHANGELOG.md

@@ -4,7 +4,7 @@
 
 - `[expect]` Support `async function`s in `toThrow` ([#9817](https://github.com/facebook/jest/pull/9817))
 - `[jest-console]` Add code frame to `console.error` and `console.warn` ([#9741](https://github.com/facebook/jest/pull/9741))
-- `[jest-runtime, jest-jasmine2, jest-circus]` Experimental, limited ECMAScript Modules support ([#9772](https://github.com/facebook/jest/pull/9772))
+- `[jest-runtime, jest-jasmine2, jest-circus]` Experimental, limited ECMAScript Modules support ([#9772](https://github.com/facebook/jest/pull/9772) & [#9842](https://github.com/facebook/jest/pull/9842))
 
 ### Fixes
 

e2e/__tests__/__snapshots__/nativeEsm.test.ts.snap

@@ -2,7 +2,7 @@
 
 exports[`on node >=12.16.0 runs test with native ESM 1`] = `
 Test Suites: 1 passed, 1 total
-Tests:       4 passed, 4 total
+Tests:       8 passed, 8 total
 Snapshots:   0 total
 Time:        <<REPLACED>>
 Ran all test suites.

e2e/native-esm/__tests__/native-esm.test.js

@@ -6,8 +6,10 @@
  */
 
 import {readFileSync} from 'fs';
+import {createRequire} from 'module';
 import {dirname, resolve} from 'path';
 import {fileURLToPath} from 'url';
+import staticImportedStateful from '../stateful.mjs';
 import {double} from '../index';
 
 test('should have correct import.meta', () => {
@@ -44,3 +46,42 @@ test('dynamic import should work', async () => {
   expect(importedDouble).toBe(double);
   expect(importedDouble(1)).toBe(2);
 });
+
+test('import cjs', async () => {
+  const {default: half} = await import('../commonjs.cjs');
+
+  expect(half(4)).toBe(2);
+});
+
+test('require(cjs) and import(cjs) should share caches', async () => {
+  const require = createRequire(import.meta.url);
+
+  const {default: importedStateful} = await import('../stateful.cjs');
+  const requiredStateful = require('../stateful.cjs');
+
+  expect(importedStateful()).toBe(1);
+  expect(importedStateful()).toBe(2);
+  expect(requiredStateful()).toBe(3);
+  expect(importedStateful()).toBe(4);
+  expect(requiredStateful()).toBe(5);
+  expect(requiredStateful()).toBe(6);
+});
+
+test('import from mjs and import(mjs) should share caches', async () => {
+  const {default: importedStateful} = await import('../stateful.mjs');
+
+  expect(importedStateful()).toBe(1);
+  expect(importedStateful()).toBe(2);
+  expect(staticImportedStateful()).toBe(3);
+  expect(importedStateful()).toBe(4);
+  expect(staticImportedStateful()).toBe(5);
+  expect(staticImportedStateful()).toBe(6);
+});
+
+test('handle unlinked dynamic imports', async () => {
+  const {double: deepDouble} = await import('../dynamicImport');
+
+  expect(deepDouble).toBe(double);
+
+  expect(deepDouble(4)).toBe(8);
+});

e2e/native-esm/commonjs.cjs

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+module.exports = function half(num) {
+  return num / 2;
+};

e2e/native-esm/dynamicImport.js

@@ -0,0 +1,8 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+export * from './index';

e2e/native-esm/stateful.cjs

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+let num = 0;
+
+module.exports = function inc() {
+  num++;
+  return num;
+};

e2e/native-esm/stateful.mjs

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+let num = 0;
+
+export default function inc() {
+  num++;
+  return num;
+}

packages/jest-runtime/src/index.ts

@@ -352,16 +352,38 @@ class Runtime {
         importModuleDynamically: (
           specifier: string,
           referencingModule: VMModule,
-        ) =>
-          this.loadEsmModule(
-            this._resolveModule(referencingModule.identifier, specifier),
-          ),
+        ) => {
+          const resolved = this._resolveModule(
+            referencingModule.identifier,
+            specifier,
+          );
+          if (
+            this._resolver.isCoreModule(resolved) ||
+            this.unstable_shouldLoadAsEsm(resolved)
+          ) {
+            return this.loadEsmModule(resolved);
+          }
+
+          return this.loadCjsAsEsm(
+            referencingModule.identifier,
+            resolved,
+            context,
+          );
+        },
         initializeImportMeta(meta: ImportMeta) {
           meta.url = pathToFileURL(modulePath).href;
         },
       });
 
       this._esmoduleRegistry.set(cacheKey, module);
+
+      await module.link((specifier: string, referencingModule: VMModule) =>
+        this.loadEsmModule(
+          this._resolveModule(referencingModule.identifier, specifier),
+        ),
+      );
+
+      await module.evaluate();
     }
 
     const module = this._esmoduleRegistry.get(cacheKey);
@@ -382,13 +404,33 @@ class Runtime {
 
     const modulePath = this._resolveModule(from, moduleName);
 
-    const module = await this.loadEsmModule(modulePath);
-    await module.link((specifier: string, referencingModule: VMModule) =>
-      this.loadEsmModule(
-        this._resolveModule(referencingModule.identifier, specifier),
-      ),
+    return this.loadEsmModule(modulePath);
+  }
+
+  private async loadCjsAsEsm(
+    from: Config.Path,
+    modulePath: Config.Path,
+    context: VMContext,
+  ) {
+    // CJS loaded via `import` should share cache with other CJS: https://github.com/nodejs/modules/issues/503
+    const cjs = this.requireModuleOrMock(from, modulePath);
+
+    const module = new SyntheticModule(
+      ['default'],
+      function () {
+        // @ts-ignore: TS doesn't know what `this` is
+        this.setExport('default', cjs);
+      },
+      {context, identifier: modulePath},
     );
+
+    await module.link(() => {
+      throw new Error('This should never happen');
+    });
+
     await module.evaluate();
+
+    return module;
   }
 
   requireModule<T = unknown>(