fix: return constructable class from require('module')

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - `[jest-environment-node]` Remove `getVmContext` from Node env on older versions of Node ([#9706](https://github.com/facebook/jest/pull/9706))
+- `[jest-runtime]` Return constructable class from `require('module')` ([#9711](https://github.com/facebook/jest/pull/9711))
 
 ### Chore & Maintenance
 

packages/jest-runtime/src/__tests__/runtime_require_module.test.js

@@ -351,6 +351,21 @@ describe('Runtime requireModule', () => {
       expect(exports.isJSONModuleEncodedInUTF8WithBOM).toBe(true);
     }));
 
+  it('should export a constructable Module class', () =>
+    createRuntime(__filename).then(runtime => {
+      const Module = runtime.requireModule(runtime.__mockRootPath, 'module');
+
+      expect(() => new Module()).not.toThrow();
+    }));
+
+  it('caches Module correctly', () =>
+    createRuntime(__filename).then(runtime => {
+      const Module1 = runtime.requireModule(runtime.__mockRootPath, 'module');
+      const Module2 = runtime.requireModule(runtime.__mockRootPath, 'module');
+
+      expect(Module1).toBe(Module2);
+    }));
+
   onNodeVersions('>=12.12.0', () => {
     it('overrides module.createRequire', () =>
       createRuntime(__filename).then(runtime => {

packages/jest-runtime/src/index.ts

@@ -122,6 +122,7 @@ class Runtime {
   private _transitiveShouldMock: BooleanObject;
   private _unmockList: RegExp | undefined;
   private _virtualMocks: BooleanObject;
+  private _moduleImplementation?: typeof nativeModule.Module;
 
   constructor(
     config: Config.ProjectConfig,
@@ -898,6 +899,17 @@ class Runtime {
     }
 
     if (moduleName === 'module') {
+      return this._getMockedNativeModule();
+    }
+
+    return require(moduleName);
+  }
+
+  private _getMockedNativeModule(): typeof nativeModule.Module {
+    if (this._moduleImplementation) {
+      return this._moduleImplementation;
+    }
+
     const createRequire = (modulePath: string | URL) => {
       const filename =
         typeof modulePath === 'string'
@@ -924,13 +936,16 @@ class Runtime {
       });
     };
 
-      const overriddenModules: Partial<typeof nativeModule> = {};
+    // should we implement the class ourselves?
+    class Module extends nativeModule.Module {}
+
+    Module.Module = Module;
 
     if ('createRequire' in nativeModule) {
-        overriddenModules.createRequire = createRequire;
+      Module.createRequire = createRequire;
     }
     if ('createRequireFromPath' in nativeModule) {
-        overriddenModules.createRequireFromPath = (filename: string | URL) => {
+      Module.createRequireFromPath = (filename: string | URL) => {
         if (typeof filename !== 'string') {
           const error = new TypeError(
             `The argument 'filename' must be string. Received '${filename}'.${
@@ -947,15 +962,12 @@ class Runtime {
       };
     }
     if ('syncBuiltinESMExports' in nativeModule) {
-        overriddenModules.syncBuiltinESMExports = () => {};
+      Module.syncBuiltinESMExports = () => {};
     }
 
-      return Object.keys(overriddenModules).length > 0
-        ? {...nativeModule, ...overriddenModules}
-        : nativeModule;
-    }
+    this._moduleImplementation = Module;
 
-    return require(moduleName);
+    return Module;
   }
 
   private _generateMock(from: Config.Path, moduleName: string) {