feat: support for transforming runner

CHANGELOG.md

@@ -6,6 +6,7 @@
 - `[jest-runner]` [**BREAKING**] set exit code to 1 if test logs after teardown ([#10728](https://github.com/facebook/jest/pull/10728))
 - `[jest-snapshot]`: [**BREAKING**] Make prettier optional for inline snapshots - fall back to string replacement ([#7792](https://github.com/facebook/jest/pull/7792))
 - `[jest-repl, jest-runner]` [**BREAKING**] Run transforms over environment ([#8751](https://github.com/facebook/jest/pull/8751))
+- `[jest-runner]` [**BREAKING**] Run transforms over `runnner` ([#8823](https://github.com/facebook/jest/pull/8823))
 
 ### Fixes
 

e2e/__tests__/transform.test.ts

@@ -216,3 +216,14 @@ describe('transform-environment', () => {
     expect(json.numPassedTests).toBe(1);
   });
 });
+
+describe('transform-runner', () => {
+  const dir = path.resolve(__dirname, '../transform/transform-runner');
+
+  it('should transform runner', () => {
+    const {json, stderr} = runWithJson(dir, ['--no-cache']);
+    expect(stderr).toMatch(/PASS/);
+    expect(json.success).toBe(true);
+    expect(json.numPassedTests).toBe(1);
+  });
+});

e2e/transform/transform-runner/__tests__/add.test.js

@@ -0,0 +1,10 @@
+/**
+ * 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.
+ */
+
+it('should add two numbers', () => {
+  expect(1 + 1).toBe(2);
+});

e2e/transform/transform-runner/babel.config.js

@@ -0,0 +1,13 @@
+/**
+ * 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 = {
+  presets: [
+    ['@babel/preset-env', {targets: {node: 'current'}}],
+    '@babel/preset-typescript',
+  ],
+};

e2e/transform/transform-runner/package.json

@@ -0,0 +1,11 @@
+{
+  "jest": {
+    "rootDir": "./",
+    "runner": "<rootDir>/runner.ts"
+  },
+  "dependencies": {
+    "@babel/preset-env": "^7.0.0",
+    "@babel/preset-typescript": "^7.0.0",
+    "jest-environment-node": "^26.6.2"
+  }
+}

e2e/transform/transform-runner/runner.ts

@@ -0,0 +1,69 @@
+/**
+ * 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 throat from 'throat';
+import {TestResult, createEmptyTestResult} from '@jest/test-result';
+import {Config} from '@jest/types';
+import {
+  OnTestFailure,
+  OnTestStart,
+  OnTestSuccess,
+  Test,
+  TestRunnerContext,
+  TestWatcher,
+} from 'jest-runner';
+
+export default class BaseTestRunner {
+  private _globalConfig: Config.GlobalConfig;
+  private _context: TestRunnerContext;
+
+  constructor(globalConfig: Config.GlobalConfig, context?: TestRunnerContext) {
+    this._globalConfig = globalConfig;
+    this._context = context || {};
+  }
+
+  async runTests(
+    tests: Array<Test>,
+    watcher: TestWatcher,
+    onStart: OnTestStart,
+    onResult: OnTestSuccess,
+    onFailure: OnTestFailure,
+  ): Promise<void> {
+    const mutex = throat(1);
+    return tests.reduce(
+      (promise, test) =>
+        mutex(() =>
+          promise
+            .then(
+              async (): Promise<TestResult> => {
+                await onStart(test);
+                return {
+                  ...createEmptyTestResult(),
+                  numPassingTests: 1,
+                  testFilePath: test.path,
+                  testResults: [
+                    {
+                      ancestorTitles: [],
+                      duration: 2,
+                      failureMessages: [],
+                      fullName: 'sample test',
+                      location: null,
+                      numPassingAsserts: 1,
+                      status: 'passed',
+                      title: 'sample test',
+                    },
+                  ],
+                };
+              },
+            )
+            .then(result => onResult(test, result))
+            .catch(err => onFailure(test, err)),
+        ),
+      Promise.resolve(),
+    );
+  }
+}

e2e/transform/transform-runner/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "compilerOptions": {
+    "esModuleInterop": true,
+    "module": "commonjs",
+  }
+}

packages/jest-core/src/TestScheduler.ts

@@ -25,6 +25,7 @@ import {
   buildFailureTestResult,
   makeEmptyAggregatedTestResult,
 } from '@jest/test-result';
+import {ScriptTransformer} from '@jest/transform';
 import type {Config} from '@jest/types';
 import {formatExecError} from 'jest-message-util';
 import TestRunner = require('jest-runner');
@@ -193,7 +194,10 @@ export default class TestScheduler {
     contexts.forEach(context => {
       const {config} = context;
       if (!testRunners[config.runner]) {
-        const Runner: typeof TestRunner = require(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

packages/jest-core/src/__tests__/TestScheduler.test.js

@@ -88,7 +88,9 @@ test('schedule tests run in parallel per default', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         runner: 'jest-runner-parallel',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),
@@ -109,7 +111,9 @@ test('schedule tests run in serial if the runner flags them', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         runner: 'jest-runner-serial',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),
@@ -130,8 +134,10 @@ test('should bail after `n` failures', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         rootDir: './',
         runner: 'jest-runner-serial',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),
@@ -160,8 +166,10 @@ test('should not bail if less than `n` failures', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         rootDir: './',
         runner: 'jest-runner-serial',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),
@@ -190,7 +198,9 @@ test('should set runInBand to run in serial', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         runner: 'jest-runner-parallel',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),
@@ -214,7 +224,9 @@ test('should set runInBand to not run in serial', async () => {
   const test = {
     context: {
       config: makeProjectConfig({
+        moduleFileExtensions: ['.js'],
         runner: 'jest-runner-parallel',
+        transform: [],
       }),
       hasteFS: {
         matchFiles: jest.fn(() => []),