fix: moduleNameMapper should take precedence over Node core modules

CHANGELOG.md

@@ -13,6 +13,7 @@
 - `[jest-matcher-utils]` Fix diff highlight of symbol-keyed object. ([#9499](https://github.com/facebook/jest/pull/9499))
 - `[jest-resolve]` Fix module identity preservation with symlinks and browser field resolution ([#9511](https://github.com/facebook/jest/pull/9511))
 - `[jest-resolve]` Do not confuse directories with files ([#8912](https://github.com/facebook/jest/pull/8912))
+- `[jest-resolve]` `moduleNameMapper` should take precedence over Node core modules ([#9563](https://github.com/facebook/jest/pull/9563))
 - `[jest-runtime]` Reset `isolateModules` if it fails ([#9541](https://github.com/facebook/jest/pull/9541))
 - `[jest-snapshot]` Downgrade semver to v6 to support node 8 ([#9451](https://github.com/facebook/jest/pull/9451))
 - `[jest-snapshot]` Properly indent new snapshots in the presences of existing ones ([#9523](https://github.com/facebook/jest/pull/9523))

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

@@ -36,7 +36,7 @@ FAIL __tests__/index.js
       12 | module.exports = () => 'test';
       13 | 
 
-      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/index.js:507:17)
+      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/index.js:519:17)
       at Object.require (index.js:10:1)
 `;
 
@@ -65,6 +65,6 @@ FAIL __tests__/index.js
       12 | module.exports = () => 'test';
       13 | 
 
-      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/index.js:507:17)
+      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/index.js:519:17)
       at Object.require (index.js:10:1)
 `;

packages/jest-resolve/src/__tests__/resolve.test.ts

@@ -45,6 +45,20 @@ describe('isCoreModule', () => {
     const isCore = resolver.isCoreModule('not-a-core-module');
     expect(isCore).toEqual(false);
   });
+
+  it('returns false if `hasCoreModules` is true and `moduleNameMapper` alias a module same name with core module', () => {
+    const moduleMap = ModuleMap.create('/');
+    const resolver = new Resolver(moduleMap, {
+      moduleNameMapper: [
+        {
+          moduleName: '$1',
+          regex: /^constants$/,
+        },
+      ],
+    } as ResolverConfig);
+    const isCore = resolver.isCoreModule('constants');
+    expect(isCore).toEqual(false);
+  });
 });
 
 describe('findNodeModule', () => {

packages/jest-resolve/src/index.ts

@@ -218,8 +218,21 @@ class Resolver {
     );
   }
 
+  private _isAliasModule(moduleName: string): boolean {
+    const moduleNameMapper = this._options.moduleNameMapper;
+    if (!moduleNameMapper) {
+      return false;
+    }
+
+    return moduleNameMapper.some(({regex}) => regex.test(moduleName));
+  }
+
   isCoreModule(moduleName: string): boolean {
-    return this._options.hasCoreModules && isBuiltinModule(moduleName);
+    return (
+      this._options.hasCoreModules &&
+      isBuiltinModule(moduleName) &&
+      !this._isAliasModule(moduleName)
+    );
   }
 
   getModule(name: string): Config.Path | null {