fix: require.main undefined with createRequire() (#10610)

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixes
 
+- `[jest-runner, jest-runtime]` fix: `require.main` undefined with `createRequire()` ([#10610](https://github.com/facebook/jest/pull/10610))
 - `[jest-validate]` Show suggestion only when unrecognized cli param is longer than 1 character ([#10604](https://github.com/facebook/jest/pull/10604))
 - `[jest-validate]` Validate `testURL` as CLI option ([#10595](https://github.com/facebook/jest/pull/10595))
 

e2e/__tests__/requireMainAfterCreateRequire.test.ts

@@ -0,0 +1,22 @@
+/**
+ * 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.
+ */
+import * as path from 'path';
+import {onNodeVersions} from '@jest/test-utils';
+import runJest from '../runJest';
+
+onNodeVersions('>=12.2.0', () => {
+  test('`require.main` not undefined after createRequire', () => {
+    const {stdout} = runJest('require-main-after-create-require');
+
+    expect(stdout).toBe(
+      path.join(
+        __dirname,
+        '../require-main-after-create-require/__tests__/parent.test.js',
+      ),
+    );
+  });
+});

e2e/require-main-after-create-require/__tests__/parent.test.js

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+const Module = require('module');
+const path = require('path');
+
+test('require child from parent', () => {
+  // createRequire with a different file
+  const newRequire = Module.createRequire(path.resolve('./empty.js'));
+  expect(() => newRequire('./child')).not.toThrow();
+});

e2e/require-main-after-create-require/child.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.
+ */
+// Will throw if require.main is null
+process.stdout.write(require.main.filename);

e2e/require-main-after-create-require/empty.js

@@ -0,0 +1,6 @@
+/**
+ * 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.
+ */

e2e/require-main-after-create-require/package.json

@@ -0,0 +1,6 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}
+

packages/jest-runner/src/runTest.ts

@@ -151,15 +151,22 @@ async function runTestInternal(
   const cacheFS = {[path]: testSource};
   setGlobal(environment.global, 'console', testConsole);
 
-  const runtime = new Runtime(config, environment, resolver, cacheFS, {
-    changedFiles: context?.changedFiles,
-    collectCoverage: globalConfig.collectCoverage,
-    collectCoverageFrom: globalConfig.collectCoverageFrom,
-    collectCoverageOnlyFrom: globalConfig.collectCoverageOnlyFrom,
-    coverageProvider: globalConfig.coverageProvider,
-    sourcesRelatedToTestsInChangedFiles:
-      context?.sourcesRelatedToTestsInChangedFiles,
-  });
+  const runtime = new Runtime(
+    config,
+    environment,
+    resolver,
+    cacheFS,
+    {
+      changedFiles: context?.changedFiles,
+      collectCoverage: globalConfig.collectCoverage,
+      collectCoverageFrom: globalConfig.collectCoverageFrom,
+      collectCoverageOnlyFrom: globalConfig.collectCoverageOnlyFrom,
+      coverageProvider: globalConfig.coverageProvider,
+      sourcesRelatedToTestsInChangedFiles:
+        context?.sourcesRelatedToTestsInChangedFiles,
+    },
+    path,
+  );
 
   const start = Date.now();
 

packages/jest-runtime/src/__mocks__/createRuntime.js

@@ -47,6 +47,9 @@ module.exports = async function createRuntime(filename, config) {
     config,
     environment,
     Runtime.createResolver(config, hasteMap.moduleMap),
+    undefined,
+    undefined,
+    filename,
   );
 
   for (const path of config.setupFiles) {

packages/jest-runtime/src/cli/index.ts

@@ -84,7 +84,14 @@ export async function run(
     setGlobal(environment.global, 'jestProjectConfig', config);
     setGlobal(environment.global, 'jestGlobalConfig', globalConfig);
 
-    const runtime = new Runtime(config, environment, hasteMap.resolver);
+    const runtime = new Runtime(
+      config,
+      environment,
+      hasteMap.resolver,
+      undefined,
+      undefined,
+      filePath,
+    );
 
     for (const path of config.setupFiles) {
       // TODO: remove ? in Jest 26

packages/jest-runtime/src/index.ts

@@ -162,6 +162,7 @@ class Runtime {
   private _isolatedModuleRegistry: ModuleRegistry | null;
   private _moduleRegistry: ModuleRegistry;
   private _esmoduleRegistry: Map<string, Promise<VMModule>>;
+  private _testPath: Config.Path | undefined;
   private _resolver: Resolver;
   private _shouldAutoMock: boolean;
   private _shouldMockModuleCache: BooleanMap;
@@ -184,6 +185,8 @@ class Runtime {
     resolver: Resolver,
     cacheFS: Record<string, string> = {},
     coverageOptions?: ShouldInstrumentOptions,
+    // TODO: Make mandatory in Jest 27
+    testPath?: Config.Path,
   ) {
     this._cacheFS = new Map(Object.entries(cacheFS));
     this._config = config;
@@ -208,6 +211,7 @@ class Runtime {
     this._isolatedMockRegistry = null;
     this._moduleRegistry = new Map();
     this._esmoduleRegistry = new Map();
+    this._testPath = testPath;
     this._resolver = resolver;
     this._scriptTransformer = new ScriptTransformer(config);
     this._shouldAutoMock = config.automock;
@@ -1365,17 +1369,7 @@ class Runtime {
 
     Object.defineProperty(moduleRequire, 'main', {
       enumerable: true,
-      get() {
-        let mainModule = from.parent;
-        while (
-          mainModule &&
-          mainModule.parent &&
-          mainModule.id !== mainModule.parent.id
-        ) {
-          mainModule = mainModule.parent;
-        }
-        return mainModule;
-      },
+      value: this._testPath ? this._moduleRegistry.get(this._testPath) : null,
     });
     return moduleRequire;
   }