fix: always load .mjs files via import

CHANGELOG.md

@@ -85,6 +85,7 @@
   - [**BREAKING**] `--testPathPattern` is now `--testPathPatterns`
   - [**BREAKING**] Specifying `testPathPatterns` when programmatically calling `watch` must be specified as `new TestPathPatterns(patterns)`, where `TestPathPatterns` can be imported from `@jest/pattern`
 - `[jest-reporters, jest-runner]` Unhandled errors without stack get correctly logged to console ([#14619](https://github.com/jestjs/jest/pull/14619))
+- `[jest-util]` Always load `mjs` files with `import` ([#15447](https://github.com/jestjs/jest/pull/15447))
 - `[jest-worker]` Properly handle a circular reference error when worker tries to send an assertion fails where either the expected or actual value is circular ([#15191](https://github.com/jestjs/jest/pull/15191))
 - `[jest-worker]` Properly handle a BigInt when worker tries to send an assertion fails where either the expected or actual value is BigInt ([#15191](https://github.com/jestjs/jest/pull/15191))
 

e2e/esm-config/js/jest.config.js

@@ -5,7 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const displayName = await Promise.resolve('Config from js file');
+
 export default {
-  displayName: 'Config from js file',
+  displayName,
   testEnvironment: 'node',
 };

e2e/esm-config/mjs/jest.config.mjs

@@ -5,7 +5,9 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+const displayName = await Promise.resolve('Config from mjs file');
+
 export default {
-  displayName: 'Config from mjs file',
+  displayName,
   testEnvironment: 'node',
 };

packages/jest-config/src/__tests__/normalize.test.ts

@@ -26,6 +26,23 @@ jest
       ...realFs,
       statSync: () => ({isDirectory: () => true}),
     };
+  })
+  .mock('jest-util', () => {
+    const realUtil =
+      jest.requireActual<typeof import('jest-util')>('jest-util');
+
+    return {
+      ...realUtil,
+      requireOrImportModule: (filePath: string, interop = true) => {
+        const result = require(filePath);
+
+        if (interop) {
+          return realUtil.interopRequireDefault(result).default;
+        }
+
+        return result;
+      },
+    };
   });
 
 let root: string;

packages/jest-util/src/requireOrImportModule.ts

@@ -9,6 +9,39 @@ import {isAbsolute} from 'path';
 import {pathToFileURL} from 'url';
 import interopRequireDefault from './interopRequireDefault';
 
+async function importModule(
+  filePath: string,
+  applyInteropRequireDefault: boolean,
+) {
+  try {
+    const moduleUrl = pathToFileURL(filePath);
+
+    // node `import()` supports URL, but TypeScript doesn't know that
+    const importedModule = await import(
+      /* webpackIgnore: true */ moduleUrl.href
+    );
+
+    if (!applyInteropRequireDefault) {
+      return importedModule;
+    }
+
+    if (!importedModule.default) {
+      throw new Error(
+        `Jest: Failed to load ESM at ${filePath} - did you use a default export?`,
+      );
+    }
+
+    return importedModule.default;
+  } catch (error: any) {
+    if (error.message === 'Not supported') {
+      throw new Error(
+        `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${filePath}`,
+      );
+    }
+    throw error;
+  }
+}
+
 export default async function requireOrImportModule<T>(
   filePath: string,
   applyInteropRequireDefault = true,
@@ -19,40 +52,21 @@ export default async function requireOrImportModule<T>(
     );
   }
   try {
+    if (filePath.endsWith('.mjs')) {
+      return importModule(filePath, applyInteropRequireDefault);
+    }
+
     const requiredModule = require(filePath);
     if (!applyInteropRequireDefault) {
       return requiredModule;
     }
     return interopRequireDefault(requiredModule).default;
   } catch (error: any) {
-    if (error.code === 'ERR_REQUIRE_ESM') {
-      try {
-        const moduleUrl = pathToFileURL(filePath);
-
-        // node `import()` supports URL, but TypeScript doesn't know that
-        const importedModule = await import(
-          /* webpackIgnore: true */ moduleUrl.href
-        );
-
-        if (!applyInteropRequireDefault) {
-          return importedModule;
-        }
-
-        if (!importedModule.default) {
-          throw new Error(
-            `Jest: Failed to load ESM at ${filePath} - did you use a default export?`,
-          );
-        }
-
-        return importedModule.default;
-      } catch (innerError: any) {
-        if (innerError.message === 'Not supported') {
-          throw new Error(
-            `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${filePath}`,
-          );
-        }
-        throw innerError;
-      }
+    if (
+      error.code === 'ERR_REQUIRE_ESM' ||
+      error.code === 'ERR_REQUIRE_ASYNC_MODULE'
+    ) {
+      return importModule(filePath, applyInteropRequireDefault);
     } else {
       throw error;
     }

yarn.lock

@@ -10555,8 +10555,8 @@ __metadata:
   linkType: hard
 
 "express@npm:^4.17.3":
-  version: 4.21.1
-  resolution: "express@npm:4.21.1"
+  version: 4.21.2
+  resolution: "express@npm:4.21.2"
   dependencies:
     accepts: ~1.3.8
     array-flatten: 1.1.1
@@ -10577,7 +10577,7 @@ __metadata:
     methods: ~1.1.2
     on-finished: 2.4.1
     parseurl: ~1.3.3
-    path-to-regexp: 0.1.10
+    path-to-regexp: 0.1.12
     proxy-addr: ~2.0.7
     qs: 6.13.0
     range-parser: ~1.2.1
@@ -10589,7 +10589,7 @@ __metadata:
     type-is: ~1.6.18
     utils-merge: 1.0.1
     vary: ~1.1.2
-  checksum: 5ac2b26d8aeddda5564fc0907227d29c100f90c0ead2ead9d474dc5108e8fb306c2de2083c4e3ba326e0906466f2b73417dbac16961f4075ff9f03785fd940fe
+  checksum: 3aef1d355622732e20b8f3a7c112d4391d44e2131f4f449e1f273a309752a41abfad714e881f177645517cbe29b3ccdc10b35e7e25c13506114244a5b72f549d
   languageName: node
   linkType: hard
 
@@ -16032,11 +16032,11 @@ __metadata:
   linkType: hard
 
 "nanoid@npm:^3.3.7":
-  version: 3.3.7
-  resolution: "nanoid@npm:3.3.7"
+  version: 3.3.8
+  resolution: "nanoid@npm:3.3.8"
   bin:
     nanoid: bin/nanoid.cjs
-  checksum: d36c427e530713e4ac6567d488b489a36582ef89da1d6d4e3b87eded11eb10d7042a877958c6f104929809b2ab0bafa17652b076cdf84324aa75b30b722204f2
+  checksum: dfe0adbc0c77e9655b550c333075f51bb28cfc7568afbf3237249904f9c86c9aaaed1f113f0fddddba75673ee31c758c30c43d4414f014a52a7a626efc5958c9
   languageName: node
   linkType: hard
 
@@ -17047,10 +17047,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"path-to-regexp@npm:0.1.10":
-  version: 0.1.10
-  resolution: "path-to-regexp@npm:0.1.10"
-  checksum: ab7a3b7a0b914476d44030340b0a65d69851af2a0f33427df1476100ccb87d409c39e2182837a96b98fb38c4ef2ba6b87bdad62bb70a2c153876b8061760583c
+"path-to-regexp@npm:0.1.12":
+  version: 0.1.12
+  resolution: "path-to-regexp@npm:0.1.12"
+  checksum: ab237858bee7b25ecd885189f175ab5b5161e7b712b360d44f5c4516b8d271da3e4bf7bf0a7b9153ecb04c7d90ce8ff5158614e1208819cf62bac2b08452722e
   languageName: node
   linkType: hard