feat(jest-transform): support transformers written in ESM

CHANGELOG.md

@@ -21,6 +21,8 @@
 - `[jest-reporters]` Add static filepath property to all reporters ([#11015](https://github.com/facebook/jest/pull/11015))
 - `[jest-snapshot]` [**BREAKING**] Make prettier optional for inline snapshots - fall back to string replacement ([#7792](https://github.com/facebook/jest/pull/7792))
 - `[jest-transform]` Pass config options defined in Jest's config to transformer's `process` and `getCacheKey` functions ([#10926](https://github.com/facebook/jest/pull/10926))
+- `[jest-transform]` Add support for transformers written in ESM ([#11163](https://github.com/facebook/jest/pull/11163))
+- `[jest-transform]` [**BREAKING**] Do not export `ScriptTransformer` class, instead export the async function `createScriptTransformer` ([#11163](https://github.com/facebook/jest/pull/11163))
 - `[jest-worker]` Add support for custom task queues and adds a `PriorityQueue` implementation. ([#10921](https://github.com/facebook/jest/pull/10921))
 - `[jest-worker]` Add in-order scheduling policy to jest worker ([10902](https://github.com/facebook/jest/pull/10902))
 

babel.config.js

@@ -35,22 +35,6 @@ module.exports = {
       ],
       test: /\.tsx?$/,
     },
-    // we want this file to keep `import()`, so exclude the transform for it
-    {
-      plugins: ['@babel/plugin-syntax-dynamic-import'],
-      presets: [
-        '@babel/preset-typescript',
-        [
-          '@babel/preset-env',
-          {
-            exclude: ['@babel/plugin-proposal-dynamic-import'],
-            shippedProposals: true,
-            targets: {node: supportedNodeVersion},
-          },
-        ],
-      ],
-      test: 'packages/jest-config/src/readConfigFileAndSetRootDir.ts',
-    },
   ],
   plugins: [
     ['@babel/plugin-transform-modules-commonjs', {allowTopLevelThis: true}],
@@ -63,6 +47,8 @@ module.exports = {
       '@babel/preset-env',
       {
         bugfixes: true,
+        // a runtime error is preferable, and we need a real `import`
+        exclude: ['@babel/plugin-proposal-dynamic-import'],
         shippedProposals: true,
         targets: {node: supportedNodeVersion},
       },

docs/Configuration.md

@@ -1295,6 +1295,8 @@ _Note: a transformer is only run once per file unless the file has changed. Duri
 
 _Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
+A transformer must be an object with at least a `process` function, and it's also recommended to include a `getCacheKey` function. If your transformer is written in ESM you should have a default export with that object.
+
 ### `transformIgnorePatterns` [array\<string>]
 
 Default: `["/node_modules/", "\\.pnp\\.[^\\\/]+$"]`

e2e/__tests__/transform.test.ts

@@ -8,6 +8,7 @@
 import {tmpdir} from 'os';
 import * as path from 'path';
 import {wrap} from 'jest-snapshot-serializer-raw';
+import {onNodeVersions} from '@jest/test-utils';
 import {
   cleanup,
   copyDir,
@@ -238,3 +239,16 @@ describe('transform-testrunner', () => {
     expect(json.numPassedTests).toBe(1);
   });
 });
+
+onNodeVersions('^12.17.0 || >=13.2.0', () => {
+  describe('esm-transformer', () => {
+    const dir = path.resolve(__dirname, '../transform/esm-transformer');
+
+    it('should transform with transformer written in ESM', () => {
+      const {json, stderr} = runWithJson(dir, ['--no-cache']);
+      expect(stderr).toMatch(/PASS/);
+      expect(json.success).toBe(true);
+      expect(json.numPassedTests).toBe(1);
+    });
+  });
+});

e2e/transform/esm-transformer/__tests__/test.js

@@ -0,0 +1,12 @@
+/**
+ * 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 m = require('../module');
+
+test('ESM transformer intercepts', () => {
+  expect(m).toEqual(42);
+});

e2e/transform/esm-transformer/module.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.
+ */
+
+module.exports = 'It was not transformed!!';

e2e/transform/esm-transformer/my-transform.mjs

@@ -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 {createRequire} from 'module';
+
+const require = createRequire(import.meta.url);
+
+const fileToTransform = require.resolve('./module');
+
+export default {
+  process(src, filepath) {
+    if (filepath === fileToTransform) {
+      return 'module.exports = 42;';
+    }
+
+    return src;
+  },
+};

e2e/transform/esm-transformer/package.json

@@ -0,0 +1,8 @@
+{
+  "jest": {
+    "testEnvironment": "node",
+    "transform": {
+      "\\.js$": "<rootDir>/my-transform.mjs"
+    }
+  }
+}

package.json

@@ -5,8 +5,6 @@
   "devDependencies": {
     "@babel/core": "^7.3.4",
     "@babel/plugin-proposal-class-properties": "^7.3.4",
-    "@babel/plugin-proposal-dynamic-import": "^7.8.3",
-    "@babel/plugin-syntax-dynamic-import": "^7.8.3",
     "@babel/plugin-transform-modules-commonjs": "^7.1.0",
     "@babel/plugin-transform-strict-mode": "^7.0.0",
     "@babel/preset-env": "^7.1.0",

packages/jest-core/src/TestScheduler.ts

@@ -25,7 +25,7 @@ import {
   buildFailureTestResult,
   makeEmptyAggregatedTestResult,
 } from '@jest/test-result';
-import {ScriptTransformer} from '@jest/transform';
+import {createScriptTransformer} from '@jest/transform';
 import type {Config} from '@jest/types';
 import {formatExecError} from 'jest-message-util';
 import TestRunner, {Test} from 'jest-runner';
@@ -188,22 +188,24 @@ export default class TestScheduler {
 
     const testRunners: {[key: string]: TestRunner} = Object.create(null);
     const contextsByTestRunner = new WeakMap<TestRunner, Context>();
-    contexts.forEach(context => {
-      const {config} = context;
-      if (!testRunners[config.runner]) {
-        const transformer = new ScriptTransformer(config);
-        const Runner: typeof TestRunner = interopRequireDefault(
-          transformer.requireAndTranspileModule(config.runner),
-        ).default;
-        const runner = new Runner(this._globalConfig, {
-          changedFiles: this._context?.changedFiles,
-          sourcesRelatedToTestsInChangedFiles: this._context
-            ?.sourcesRelatedToTestsInChangedFiles,
-        });
-        testRunners[config.runner] = runner;
-        contextsByTestRunner.set(runner, context);
-      }
-    });
+    await Promise.all(
+      Array.from(contexts).map(async context => {
+        const {config} = context;
+        if (!testRunners[config.runner]) {
+          const transformer = await createScriptTransformer(config);
+          const Runner: typeof TestRunner = interopRequireDefault(
+            transformer.requireAndTranspileModule(config.runner),
+          ).default;
+          const runner = new Runner(this._globalConfig, {
+            changedFiles: this._context?.changedFiles,
+            sourcesRelatedToTestsInChangedFiles: this._context
+              ?.sourcesRelatedToTestsInChangedFiles,
+          });
+          testRunners[config.runner] = runner;
+          contextsByTestRunner.set(runner, context);
+        }
+      }),
+    );
 
     const testsByRunner = this._partitionTests(testRunners, tests);
 

packages/jest-core/src/__tests__/watchFileChanges.test.ts

@@ -14,6 +14,7 @@ import type {AggregatedResult} from '@jest/test-result';
 import {normalize} from 'jest-config';
 import type HasteMap from 'jest-haste-map';
 import Runtime from 'jest-runtime';
+import {interopRequireDefault} from 'jest-util';
 import {JestHook} from 'jest-watcher';
 
 describe('Watch mode flows with changed files', () => {
@@ -31,8 +32,8 @@ describe('Watch mode flows with changed files', () => {
   const cacheDirectory = path.resolve(tmpdir(), `tmp${Math.random()}`);
   let hasteMapInstance: HasteMap;
 
-  beforeEach(async () => {
-    watch = (await import('../watch')).default;
+  beforeEach(() => {
+    watch = interopRequireDefault(require('../watch')).default;
     pipe = {write: jest.fn()} as unknown;
     stdin = new MockStdin();
     rimraf.sync(cacheDirectory);

packages/jest-core/src/runGlobalHook.ts

@@ -7,7 +7,7 @@
 
 import * as util from 'util';
 import pEachSeries = require('p-each-series');
-import {ScriptTransformer} from '@jest/transform';
+import {createScriptTransformer} from '@jest/transform';
 import type {Config} from '@jest/types';
 import type {Test} from 'jest-runner';
 import {interopRequireDefault} from 'jest-util';
@@ -45,7 +45,7 @@ export default async ({
         : // Fallback to first config
           allTests[0].context.config;
 
-      const transformer = new ScriptTransformer(projectConfig);
+      const transformer = await createScriptTransformer(projectConfig);
 
       try {
         await transformer.requireAndTranspileModule(modulePath, async m => {

packages/jest-create-cache-key-function/package.json

@@ -10,7 +10,8 @@
     "@jest/types": "^27.0.0-next.3"
   },
   "devDependencies": {
-    "@types/node": "*"
+    "@types/node": "*",
+    "jest-util": "^27.0.0-next.3"
   },
   "engines": {
     "node": "^10.13.0 || ^12.13.0 || ^14.15.0 || >=15.0.0"

packages/jest-create-cache-key-function/src/__tests__/index.test.ts

@@ -5,6 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import {interopRequireDefault} from 'jest-util';
+
 let NODE_ENV: string;
 let BABEL_ENV: string;
 
@@ -20,8 +22,9 @@ afterEach(() => {
   process.env.BABEL_ENV = BABEL_ENV;
 });
 
-test('creation of a cache key', async () => {
-  const createCacheKeyFunction = (await import('../index')).default;
+test('creation of a cache key', () => {
+  const createCacheKeyFunction = interopRequireDefault(require('../index'))
+    .default;
   const createCacheKey = createCacheKeyFunction([], ['value']);
   const hashA = createCacheKey('test', 'test.js', null, {
     config: {},

packages/jest-create-cache-key-function/tsconfig.json

@@ -4,7 +4,5 @@
     "rootDir": "src",
     "outDir": "build"
   },
-  "references": [
-    {"path":  "../jest-types"}
-  ]
+  "references": [{"path": "../jest-types"}, {"path": "../jest-util"}]
 }

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

@@ -11,7 +11,7 @@ import chalk = require('chalk');
 import yargs = require('yargs');
 import {CustomConsole} from '@jest/console';
 import type {JestEnvironment} from '@jest/environment';
-import {ScriptTransformer} from '@jest/transform';
+import {createScriptTransformer} from '@jest/transform';
 import type {Config} from '@jest/types';
 import {deprecationEntries, readConfig} from 'jest-config';
 import Runtime from 'jest-runtime';
@@ -74,7 +74,7 @@ export async function run(
       watchman: globalConfig.watchman,
     });
 
-    const transformer = new ScriptTransformer(config);
+    const transformer = await createScriptTransformer(config);
     const Environment: typeof JestEnvironment = interopRequireDefault(
       transformer.requireAndTranspileModule(config.testEnvironment),
     ).default;
@@ -91,6 +91,7 @@ export async function run(
       config,
       environment,
       hasteMap.resolver,
+      transformer,
       new Map(),
       {
         changedFiles: undefined,

packages/jest-reporters/src/CoverageWorker.ts

@@ -33,7 +33,7 @@ export function worker({
   globalConfig,
   path,
   options,
-}: CoverageWorkerData): CoverageWorkerResult | null {
+}: CoverageWorkerData): Promise<CoverageWorkerResult | null> {
   return generateEmptyCoverage(
     fs.readFileSync(path, 'utf8'),
     path,

packages/jest-reporters/src/__tests__/generateEmptyCoverage.test.js

@@ -24,7 +24,7 @@ describe('generateEmptyCoverage', () => {
   const rootDir = __dirname;
   const filepath = path.join(rootDir, './sum.js');
 
-  it('generates an empty coverage object for a file without running it', () => {
+  it('generates an empty coverage object for a file without running it', async () => {
     const src = `
     throw new Error('this should not be thrown');
 
@@ -42,7 +42,7 @@ describe('generateEmptyCoverage', () => {
 
     shouldInstrument.mockReturnValueOnce(true);
 
-    const emptyCoverage = generateEmptyCoverage(
+    const emptyCoverage = await generateEmptyCoverage(
       src,
       filepath,
       makeGlobalConfig(),
@@ -71,7 +71,7 @@ describe('generateEmptyCoverage', () => {
     });
   });
 
-  it('generates a null coverage result when using /* istanbul ignore file */', () => {
+  it('generates a null coverage result when using /* istanbul ignore file */', async () => {
     const src = `
     /* istanbul ignore file */
     const a = (b, c) => {
@@ -86,7 +86,7 @@ describe('generateEmptyCoverage', () => {
 
     shouldInstrument.mockReturnValueOnce(true);
 
-    const nullCoverage = generateEmptyCoverage(
+    const nullCoverage = await generateEmptyCoverage(
       src,
       filepath,
       makeGlobalConfig(),
@@ -101,7 +101,7 @@ describe('generateEmptyCoverage', () => {
     expect(nullCoverage).toBeNull();
   });
 
-  it('generates a null coverage result when collectCoverage global config is false', () => {
+  it('generates a null coverage result when collectCoverage global config is false', async () => {
     const src = `
     const a = (b, c) => {
       if (b) {
@@ -115,7 +115,7 @@ describe('generateEmptyCoverage', () => {
 
     shouldInstrument.mockReturnValueOnce(false);
 
-    const nullCoverage = generateEmptyCoverage(
+    const nullCoverage = await generateEmptyCoverage(
       src,
       filepath,
       makeGlobalConfig(),