fix(esm): handle parallel imports (#9858)

CHANGELOG.md

@@ -8,6 +8,7 @@
 ### Fixes
 
 - `[jest-runtime]` Support importing CJS from ESM using `import` statements ([#9850](https://github.com/facebook/jest/pull/9850))
+- `[jest-runtime]` Support importing parallel dynamic `import`s ([#9858](https://github.com/facebook/jest/pull/9858))
 
 ### Chore & Maintenance
 

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

@@ -2,7 +2,7 @@
 
 exports[`on node ^12.16.0 || >=13.2.0 runs test with native ESM 1`] = `
 Test Suites: 1 passed, 1 total
-Tests:       10 passed, 10 total
+Tests:       11 passed, 11 total
 Snapshots:   0 total
 Time:        <<REPLACED>>
 Ran all test suites.

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

@@ -95,3 +95,13 @@ test('handle unlinked dynamic imports', async () => {
 test('can import `jest` object', () => {
   expect(jestObject).toBeDefined();
 });
+
+test('handle dynamic imports of the same module in parallel', async () => {
+  const [{double: first}, {double: second}] = await Promise.all([
+    import('../anotherDynamicImport.js'),
+    import('../anotherDynamicImport.js'),
+  ]);
+
+  expect(first).toBe(second);
+  expect(first(2)).toBe(4);
+});

e2e/native-esm/anotherDynamicImport.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';

packages/jest-runtime/src/index.ts

@@ -139,7 +139,7 @@ class Runtime {
   private _moduleMocker: typeof jestMock;
   private _isolatedModuleRegistry: ModuleRegistry | null;
   private _moduleRegistry: ModuleRegistry;
-  private _esmoduleRegistry: Map<string, VMModule>;
+  private _esmoduleRegistry: Map<string, Promise<VMModule>>;
   private _needsCoverageMapped: Set<string>;
   private _resolver: Resolver;
   private _shouldAutoMock: boolean;
@@ -358,11 +358,16 @@ class Runtime {
         },
       });
 
-      this._esmoduleRegistry.set(cacheKey, module);
-
-      await module.link(this.linkModules.bind(this));
-
-      await module.evaluate();
+      this._esmoduleRegistry.set(
+        cacheKey,
+        // we wanna put the linking promise in the cache so modules loaded in
+        // parallel can all await it. We then await it synchronously below, so
+        // we shouldn't get any unhandled rejections
+        module
+          .link(this.linkModules.bind(this))
+          .then(() => module.evaluate())
+          .then(() => module),
+      );
     }
 
     const module = this._esmoduleRegistry.get(cacheKey);