feat: add support for .mjs config

CHANGELOG.md

@@ -12,6 +12,7 @@
 - `[jest-config]` [**BREAKING**] Set default display name color based on runner ([#8689](https://github.com/facebook/jest/pull/8689))
 - `[jest-config]` Merge preset globals with project globals ([#9027](https://github.com/facebook/jest/pull/9027))
 - `[jest-config]` Support `.cjs` config files ([#9291](https://github.com/facebook/jest/pull/9291))
+- `[jest-config]` [**BREAKING**] Support `.mjs` config files ([#9431](https://github.com/facebook/jest/pull/9431))
 - `[jest-core]` Support reporters as default exports ([#9161](https://github.com/facebook/jest/pull/9161))
 - `[jest-core]` Support `--findRelatedTests` paths case insensitivity on Windows ([#8900](https://github.com/facebook/jest/issues/8900))
 - `[jest-diff]` Add options for colors and symbols ([#8841](https://github.com/facebook/jest/pull/8841))

babel.config.js

@@ -19,6 +19,22 @@ module.exports = {
       presets: ['@babel/preset-typescript'],
       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: 8},
+          },
+        ],
+      ],
+      test: 'packages/jest-config/src/readConfigFileAndSetRootDir.ts',
+    },
   ],
   plugins: [
     ['@babel/plugin-transform-modules-commonjs', {allowTopLevelThis: true}],

e2e/__tests__/esmConfigFile.test.ts

@@ -0,0 +1,38 @@
+/**
+ * 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 {onNodeVersions} from '@jest/test-utils';
+import {json as runWithJson} from '../runJest';
+
+test('reads config from cjs file', () => {
+  const {json, exitCode} = runWithJson('esm-config/cjs', ['--show-config'], {
+    skipPkgJsonCheck: true,
+  });
+
+  expect(exitCode).toBe(0);
+  expect(json.configs).toHaveLength(1);
+  expect(json.configs[0].displayName).toEqual({
+    color: 'white',
+    name: 'Config from cjs file',
+  });
+});
+
+// not unflagged for other versions yet. Update this range if that changes
+onNodeVersions('^13.2.0', () => {
+  test('reads config from mjs file', () => {
+    const {json, exitCode} = runWithJson('esm-config/mjs', ['--show-config'], {
+      skipPkgJsonCheck: true,
+    });
+
+    expect(exitCode).toBe(0);
+    expect(json.configs).toHaveLength(1);
+    expect(json.configs[0].displayName).toEqual({
+      color: 'white',
+      name: 'Config from mjs file',
+    });
+  });
+});

e2e/esm-config/mjs/__tests__/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.
+ */
+
+test('dummy test', () => {
+  expect(1).toBe(1);
+});

e2e/esm-config/mjs/jest.config.mjs

@@ -0,0 +1,11 @@
+/**
+ * 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.
+ */
+
+export default {
+  displayName: 'Config from mjs file',
+  testEnvironment: 'node',
+};

e2e/esm-config/mjs/package.json

@@ -0,0 +1,3 @@
+{
+  "jest": {}
+}

packages/jest-cli/src/init/__tests__/__snapshots__/init.test.js.snap

@@ -36,6 +36,207 @@ Object {
 }
 `;
 
+exports[`init has-jest-config-file-mjs ask the user whether to override config or not user answered with "Yes" 1`] = `
+Object {
+  "initial": true,
+  "message": "It seems that you already have a jest configuration, do you want to override it?",
+  "name": "continue",
+  "type": "confirm",
+}
+`;
+
+exports[`init project with package.json and no jest config all questions answered with answer: "No" should generate empty config with mjs extension 1`] = `
+"// For a detailed explanation regarding each configuration property, visit:
+// https://jestjs.io/docs/en/configuration.html
+
+export default {
+  // All imported modules in your tests should be mocked automatically
+  // automock: false,
+
+  // Stop running tests after \`n\` failures
+  // bail: 0,
+
+  // Respect \\"browser\\" field in package.json when resolving modules
+  // browser: false,
+
+  // The directory where Jest should store its cached dependency information
+  // cacheDirectory: \\"/tmp/jest\\",
+
+  // Automatically clear mock calls and instances between every test
+  // clearMocks: false,
+
+  // Indicates whether the coverage information should be collected while executing the test
+  // collectCoverage: false,
+
+  // An array of glob patterns indicating a set of files for which coverage information should be collected
+  // collectCoverageFrom: undefined,
+
+  // The directory where Jest should output its coverage files
+  // coverageDirectory: undefined,
+
+  // An array of regexp pattern strings used to skip coverage collection
+  // coveragePathIgnorePatterns: [
+  //   \\"/node_modules/\\"
+  // ],
+
+  // A list of reporter names that Jest uses when writing coverage reports
+  // coverageReporters: [
+  //   \\"json\\",
+  //   \\"text\\",
+  //   \\"lcov\\",
+  //   \\"clover\\"
+  // ],
+
+  // An object that configures minimum threshold enforcement for coverage results
+  // coverageThreshold: undefined,
+
+  // A path to a custom dependency extractor
+  // dependencyExtractor: undefined,
+
+  // Make calling deprecated APIs throw helpful error messages
+  // errorOnDeprecated: false,
+
+  // Force coverage collection from ignored files using an array of glob patterns
+  // forceCoverageMatch: [],
+
+  // A path to a module which exports an async function that is triggered once before all test suites
+  // globalSetup: undefined,
+
+  // A path to a module which exports an async function that is triggered once after all test suites
+  // globalTeardown: undefined,
+
+  // A set of global variables that need to be available in all test environments
+  // globals: {},
+
+  // The maximum amount of workers used to run your tests. Can be specified as % or a number. E.g. maxWorkers: 10% will use 10% of your CPU amount + 1 as the maximum worker number. maxWorkers: 2 will use a maximum of 2 workers.
+  // maxWorkers: \\"50%\\",
+
+  // An array of directory names to be searched recursively up from the requiring module's location
+  // moduleDirectories: [
+  //   \\"node_modules\\"
+  // ],
+
+  // An array of file extensions your modules use
+  // moduleFileExtensions: [
+  //   \\"js\\",
+  //   \\"json\\",
+  //   \\"jsx\\",
+  //   \\"ts\\",
+  //   \\"tsx\\",
+  //   \\"node\\"
+  // ],
+
+  // A map from regular expressions to module names that allow to stub out resources with a single module
+  // moduleNameMapper: {},
+
+  // An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
+  // modulePathIgnorePatterns: [],
+
+  // Activates notifications for test results
+  // notify: false,
+
+  // An enum that specifies notification mode. Requires { notify: true }
+  // notifyMode: \\"failure-change\\",
+
+  // A preset that is used as a base for Jest's configuration
+  // preset: undefined,
+
+  // Run tests from one or more projects
+  // projects: undefined,
+
+  // Use this configuration option to add custom reporters to Jest
+  // reporters: undefined,
+
+  // Automatically reset mock state between every test
+  // resetMocks: false,
+
+  // Reset the module registry before running each individual test
+  // resetModules: false,
+
+  // A path to a custom resolver
+  // resolver: undefined,
+
+  // Automatically restore mock state between every test
+  // restoreMocks: false,
+
+  // The root directory that Jest should scan for tests and modules within
+  // rootDir: undefined,
+
+  // A list of paths to directories that Jest should use to search for files in
+  // roots: [
+  //   \\"<rootDir>\\"
+  // ],
+
+  // Allows you to use a custom runner instead of Jest's default test runner
+  // runner: \\"jest-runner\\",
+
+  // The paths to modules that run some code to configure or set up the testing environment before each test
+  // setupFiles: [],
+
+  // A list of paths to modules that run some code to configure or set up the testing framework before each test
+  // setupFilesAfterEnv: [],
+
+  // A list of paths to snapshot serializer modules Jest should use for snapshot testing
+  // snapshotSerializers: [],
+
+  // The test environment that will be used for testing
+  // testEnvironment: \\"jest-environment-jsdom\\",
+
+  // Options that will be passed to the testEnvironment
+  // testEnvironmentOptions: {},
+
+  // Adds a location field to test results
+  // testLocationInResults: false,
+
+  // The glob patterns Jest uses to detect test files
+  // testMatch: [
+  //   \\"**/__tests__/**/*.[jt]s?(x)\\",
+  //   \\"**/?(*.)+(spec|test).[tj]s?(x)\\"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
+  // testPathIgnorePatterns: [
+  //   \\"/node_modules/\\"
+  // ],
+
+  // The regexp pattern or array of patterns that Jest uses to detect test files
+  // testRegex: [],
+
+  // This option allows the use of a custom results processor
+  // testResultsProcessor: undefined,
+
+  // This option allows use of a custom test runner
+  // testRunner: \\"jasmine2\\",
+
+  // This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
+  // testURL: \\"http://localhost\\",
+
+  // Setting this value to \\"fake\\" allows the use of fake timers for functions such as \\"setTimeout\\"
+  // timers: \\"real\\",
+
+  // A map from regular expressions to paths to transformers
+  // transform: undefined,
+
+  // An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
+  // transformIgnorePatterns: [
+  //   \\"/node_modules/\\"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
+  // unmockedModulePathPatterns: undefined,
+
+  // Indicates whether each individual test should be reported during the run
+  // verbose: undefined,
+
+  // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
+  // watchPathIgnorePatterns: [],
+
+  // Whether to use watchman for file crawling
+  // watchman: true,
+};
+"
+`;
+
 exports[`init project with package.json and no jest config all questions answered with answer: "No" should return the default configuration (an empty config) 1`] = `
 "// For a detailed explanation regarding each configuration property, visit:
 // https://jestjs.io/docs/en/configuration.html

packages/jest-cli/src/init/__tests__/fixtures/has_jest_config_file_mjs/jest.config.mjs

@@ -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.
+ */
+
+export default {};

packages/jest-cli/src/init/__tests__/fixtures/has_jest_config_file_mjs/package.json

@@ -0,0 +1 @@
+{}

packages/jest-cli/src/init/__tests__/fixtures/type_module/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "type_module",
+  "scripts": {
+    "test": "different-test-runner"
+  },
+  "type": "module"
+}

packages/jest-cli/src/init/__tests__/init.test.js

@@ -9,8 +9,11 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import prompts from 'prompts';
+import {constants} from 'jest-config';
 import init from '../';
-import {JEST_CONFIG_EXT_ORDER} from '../constants';
+import {onNodeVersions} from '@jest/test-utils';
+
+const {JEST_CONFIG_EXT_ORDER} = constants;
 
 jest.mock('prompts');
 jest.mock('../../../../jest-config/build/getCacheDirectory', () => () =>
@@ -52,6 +55,20 @@ describe('init', () => {
 
         expect(evaluatedConfig).toEqual({});
       });
+
+      onNodeVersions('^13.1.0', () => {
+        it('should generate empty config with mjs extension', async () => {
+          prompts.mockReturnValueOnce({});
+
+          await init(resolveFromFixture('type_module'));
+
+          expect(fs.writeFileSync.mock.calls[0][0].endsWith('.mjs')).toBe(true);
+
+          const writtenJestConfig = fs.writeFileSync.mock.calls[0][1];
+
+          expect(writtenJestConfig).toMatchSnapshot();
+        });
+      });
     });
 
     describe('some questions answered with answer: "Yes"', () => {