fix: transform js ESM file from node_modules

`ts.LanguageService` somehow can't transform `js` file which has content in ESM.

When dealing with those files, we simply transform them with `ts.transpileModule` API without applying any AST transformers. We don't apply type-check on these files either since they are prebuilt. This should benefit the performance and help users to work easier with ESM packages when running Jest in CJS mode.

Fixes #2913

e2e/process-js-packages/__tests__/process-js-packages.spec.ts

@@ -1,7 +1,9 @@
 import camelCase from 'lodash-es/camelCase';
+import { union } from 'set-utilities';
 import { __assign } from 'tslib';
 
 test('should pass', () => {
     expect(camelCase('foo-bar')).toBe('fooBar');
     expect(typeof __assign).toBe('function');
+    expect(union(new Set([1, 2, 3]), new Set([4, 5, 6]))).toStrictEqual(new Set([1, 2, 3, 4, 5, 6]));
 });

e2e/process-js-packages/jest-cjs.config.ts

@@ -16,7 +16,7 @@ const config: JestConfigWithTsJest = {
             },
         ],
     },
-    transformIgnorePatterns: ['node_modules/(?!lodash-es)'],
+    transformIgnorePatterns: ['node_modules/(?!lodash-es|set-utilities)'],
 };
 
 export default config;

e2e/process-js-packages/jest-transpile-cjs.config.ts

@@ -17,7 +17,7 @@ const config: JestConfigWithTsJest = {
             },
         ],
     },
-    transformIgnorePatterns: ['node_modules/(?!lodash-es)'],
+    transformIgnorePatterns: ['node_modules/(?!lodash-es|set-utilities)'],
 };
 
 export default config;

e2e/process-js-packages/package.json

@@ -3,6 +3,7 @@
   "private": true,
   "devDependencies": {
     "@types/lodash-es": "^4.17.12",
-    "lodash-es": "^4.17.21"
+    "lodash-es": "^4.17.21",
+    "set-utilities": "^1.5.7"
   }
 }

e2e/process-js-packages/yarn.lock

@@ -34,5 +34,13 @@ __metadata:
   dependencies:
     "@types/lodash-es": "npm:^4.17.12"
     lodash-es: "npm:^4.17.21"
+    set-utilities: "npm:^1.5.7"
   languageName: unknown
   linkType: soft
+
+"set-utilities@npm:^1.5.7":
+  version: 1.5.7
+  resolution: "set-utilities@npm:1.5.7"
+  checksum: 10/d36f10778cb31bd2e6e5521473dbe9df1dd8e7ff86300910134aa0c7397da4845a4d058ffb773a1079b2ed2f9b85b76a5880921588cf211430e930eda171cfc5
+  languageName: node
+  linkType: hard

src/ng-jest-transformer.spec.ts

@@ -1,5 +1,6 @@
 import { transformSync } from 'esbuild';
 import { TsJestTransformer } from 'ts-jest';
+import { transpileModule } from 'typescript';
 
 import packageJson from '../package.json';
 import { NgJestCompiler } from './compiler/ng-jest-compiler';
@@ -15,11 +16,21 @@ jest.mock('esbuild', () => {
     };
 });
 const mockedTransformSync = jest.mocked(transformSync);
+jest.mock('typescript', () => {
+    return {
+        ...jest.requireActual('typescript'),
+        transpileModule: jest.fn().mockReturnValue({
+            outputText: '',
+        }),
+    };
+});
+const mockTranspileModule = jest.mocked(transpileModule);
 
 describe('NgJestTransformer', () => {
     beforeEach(() => {
         // @ts-expect-error testing purpose
         TsJestTransformer._cachedConfigSets = [];
+        mockTranspileModule.mockClear();
     });
 
     test('should create NgJestCompiler and NgJestConfig instances', () => {
@@ -148,6 +159,30 @@ describe('NgJestTransformer', () => {
         mockedTransformSync.mockClear();
     });
 
+    it('should use "transpileModule" to process `node_modules` js file', () => {
+        const transformCfg = {
+            cacheFS: new Map(),
+            config: {
+                cwd: process.cwd(),
+                extensionsToTreatAsEsm: [],
+                testMatch: [],
+                testRegex: [],
+            },
+        } as any; // eslint-disable-line @typescript-eslint/no-explicit-any
+        const tr = new NgJestTransformer({});
+        tr.process(
+            `
+      const pi = parseFloat(3.124);
+
+      export { pi };
+    `,
+            'node_modules/random-package/foo.js',
+            transformCfg,
+        );
+
+        expect(mockTranspileModule.mock.calls[0][1].fileName).toBe('node_modules/random-package/foo.js');
+    });
+
     test.each([
         {
             tsconfig: {

src/ng-jest-transformer.ts

@@ -4,6 +4,8 @@ import type { TransformedSource } from '@jest/transform';
 import { LogContexts, LogLevels, type Logger, createLogger } from 'bs-logger';
 import { transformSync } from 'esbuild';
 import { type TsJestTransformerOptions, ConfigSet, TsJestTransformer, type TsJestTransformOptions } from 'ts-jest';
+import { updateOutput } from 'ts-jest/dist/legacy/compiler/compiler-utils';
+import type { TranspileOutput } from 'typescript';
 
 import { NgJestCompiler } from './compiler/ng-jest-compiler';
 import { NgJestConfig } from './config/ng-jest-config';
@@ -93,6 +95,27 @@ export class NgJestTransformer extends TsJestTransformer {
                 map,
             };
         } else {
+            if (filePath.includes('node_modules') && filePath.endsWith('.js')) {
+                /**
+                 * Simply transform the file without applying any extra AST transformers. We might consider to support using AST transformers on `node_modules` files when there are requests.
+                 * Since the files in `node_modules` are prebuilt, we don't need to perform type check on these files which should benefit the performance.
+                 */
+                const result: TranspileOutput = configSet.compilerModule.transpileModule(fileContent, {
+                    compilerOptions: {
+                        ...configSet.parsedTsConfig.options,
+                        module:
+                            transformOptions.supportsStaticESM && configSet.useESM
+                                ? configSet.parsedTsConfig.options.module
+                                : configSet.compilerModule.ModuleKind.CommonJS,
+                    },
+                    fileName: filePath,
+                });
+
+                return {
+                    code: updateOutput(result.outputText, filePath, result.sourceMapText),
+                };
+            }
+
             return super.process(fileContent, filePath, transformOptions);
         }
     }