Support '.js', '.cjs', '.json' configs

CHANGELOG.md

@@ -11,6 +11,7 @@
 - `[jest-config]` Throw the full error message and stack when a Jest preset is missing a dependency ([#8924](https://github.com/facebook/jest/pull/8924))
 - `[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-core]` Support reporters as default exports ([#9161](https://github.com/facebook/jest/pull/9161))
 - `[jest-diff]` Add options for colors and symbols ([#8841](https://github.com/facebook/jest/pull/8841))
 - `[jest-diff]` [**BREAKING**] Export as ECMAScript module ([#8873](https://github.com/facebook/jest/pull/8873))

docs/Configuration.md

@@ -3,7 +3,7 @@ id: configuration
 title: Configuring Jest
 ---
 
-Jest's configuration can be defined in the `package.json` file of your project, or through a `jest.config.js` file or through the `--config <path/to/js|json>` option. If you'd like to use your `package.json` to store Jest's config, the "jest" key should be used on the top level so Jest will know how to find your settings:
+Jest's configuration can be defined in the `package.json` file of your project, or through a `jest.config.js` file or through the `--config <path/to/file.js|cjs|json>` option. If you'd like to use your `package.json` to store Jest's config, the "jest" key should be used on the top level so Jest will know how to find your settings:
 
 ```json
 {

e2e/__tests__/cjsConfigFile.test.ts

@@ -0,0 +1,21 @@
+/**
+ * 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 {json as runWithJson} from '../runJest';
+
+test('reads config from cjs file', () => {
+  const {json, exitCode} = runWithJson('cjs-config', ['--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',
+  });
+});

e2e/cjs-config/__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/cjs-config/jest.config.cjs

@@ -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.
+ */
+
+module.exports = {
+  displayName: 'Config from cjs file',
+  testEnvironment: 'node',
+};

e2e/cjs-config/package.json

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

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

@@ -9,7 +9,25 @@ Object {
 }
 `;
 
-exports[`init has-jest-config-file ask the user whether to override config or not user answered with "Yes" 1`] = `
+exports[`init has-jest-config-file-cjs 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 has-jest-config-file-js 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 has-jest-config-file-json 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?",

packages/jest-cli/src/init/__tests__/fixtures/has_jest_config_file_js/jest.config.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 = {};

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

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

packages/jest-cli/src/init/__tests__/fixtures/has_jest_config_file_json/jest.config.json

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

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

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

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

@@ -10,6 +10,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import prompts from 'prompts';
 import init from '../';
+import {JEST_CONFIG_EXT_ORDER} from '../constants';
 
 jest.mock('prompts');
 jest.mock('../../../../jest-config/build/getCacheDirectory', () => () =>
@@ -125,29 +126,32 @@ describe('init', () => {
     });
   });
 
-  describe('has-jest-config-file', () => {
-    describe('ask the user whether to override config or not', () => {
-      it('user answered with "Yes"', async () => {
-        prompts.mockReturnValueOnce({continue: true}).mockReturnValueOnce({});
+  describe.each(JEST_CONFIG_EXT_ORDER.map(e => e.substring(1)))(
+    'has-jest-config-file-%s',
+    extension => {
+      describe('ask the user whether to override config or not', () => {
+        it('user answered with "Yes"', async () => {
+          prompts.mockReturnValueOnce({continue: true}).mockReturnValueOnce({});
 
-        await init(resolveFromFixture('has_jest_config_file'));
+          await init(resolveFromFixture(`has_jest_config_file_${extension}`));
 
-        expect(prompts.mock.calls[0][0]).toMatchSnapshot();
+          expect(prompts.mock.calls[0][0]).toMatchSnapshot();
 
-        const writtenJestConfig = fs.writeFileSync.mock.calls[0][1];
+          const writtenJestConfig = fs.writeFileSync.mock.calls[0][1];
 
-        expect(writtenJestConfig).toBeDefined();
-      });
+          expect(writtenJestConfig).toBeDefined();
+        });
 
-      it('user answered with "No"', async () => {
-        prompts.mockReturnValueOnce({continue: false});
+        it('user answered with "No"', async () => {
+          prompts.mockReturnValueOnce({continue: false});
 
-        await init(resolveFromFixture('has_jest_config_file'));
-        // return after first prompt
-        expect(prompts).toHaveBeenCalledTimes(1);
+          await init(resolveFromFixture(`has_jest_config_file_${extension}`));
+          // return after first prompt
+          expect(prompts).toHaveBeenCalledTimes(1);
+        });
       });
-    });
-  });
+    },
+  );
 
   describe('has jest config in package.json', () => {
     it('should ask the user whether to override config or not', async () => {

packages/jest-cli/src/init/constants.ts

@@ -6,4 +6,12 @@
  */
 
 export const PACKAGE_JSON = 'package.json';
-export const JEST_CONFIG = 'jest.config.js';
+export const JEST_CONFIG_BASE_NAME = 'jest.config';
+export const JEST_CONFIG_EXT_CJS = '.cjs';
+export const JEST_CONFIG_EXT_JS = '.js';
+export const JEST_CONFIG_EXT_JSON = '.json';
+export const JEST_CONFIG_EXT_ORDER = Object.freeze([
+  JEST_CONFIG_EXT_JS,
+  JEST_CONFIG_EXT_CJS,
+  JEST_CONFIG_EXT_JSON,
+]);

packages/jest-cli/src/init/index.ts

@@ -12,7 +12,13 @@ import prompts = require('prompts');
 import {sync as realpath} from 'realpath-native';
 import defaultQuestions, {testScriptQuestion} from './questions';
 import {MalformedPackageJsonError, NotFoundPackageJsonError} from './errors';
-import {JEST_CONFIG, PACKAGE_JSON} from './constants';
+import {
+  JEST_CONFIG_BASE_NAME,
+  JEST_CONFIG_EXT_CJS,
+  JEST_CONFIG_EXT_JS,
+  JEST_CONFIG_EXT_ORDER,
+  PACKAGE_JSON,
+} from './constants';
 import generateConfigFile from './generate_config_file';
 import modifyPackageJson from './modify_package_json';
 import {ProjectPackageJson} from './types';
@@ -24,18 +30,18 @@ type PromptsResults = {
   scripts: boolean;
 };
 
+const getConfigFilename = (ext: string) => JEST_CONFIG_BASE_NAME + ext;
+
 export default async (rootDir: string = realpath(process.cwd())) => {
   // prerequisite checks
   const projectPackageJsonPath: string = path.join(rootDir, PACKAGE_JSON);
-  const jestConfigPath: string = path.join(rootDir, JEST_CONFIG);
 
   if (!fs.existsSync(projectPackageJsonPath)) {
     throw new NotFoundPackageJsonError(rootDir);
   }
 
   const questions = defaultQuestions.slice(0);
   let hasJestProperty: boolean = false;
-  let hasJestConfig: boolean = false;
   let projectPackageJson: ProjectPackageJson;
 
   try {
@@ -50,11 +56,21 @@ export default async (rootDir: string = realpath(process.cwd())) => {
     hasJestProperty = true;
   }
 
-  if (fs.existsSync(jestConfigPath)) {
-    hasJestConfig = true;
-  }
+  const existingJestConfigPath = JEST_CONFIG_EXT_ORDER.find(ext =>
+    fs.existsSync(path.join(rootDir, getConfigFilename(ext))),
+  );
+  const jestConfigPath =
+    existingJestConfigPath ||
+    path.join(
+      rootDir,
+      getConfigFilename(
+        projectPackageJson.type === 'module'
+          ? JEST_CONFIG_EXT_CJS
+          : JEST_CONFIG_EXT_JS,
+      ),
+    );
 
-  if (hasJestProperty || hasJestConfig) {
+  if (hasJestProperty || existingJestConfigPath) {
     const result: {continue: boolean} = await prompts({
       initial: true,
       message:

packages/jest-cli/src/init/types.ts

@@ -10,4 +10,5 @@ import {Config} from '@jest/types';
 export type ProjectPackageJson = {
   jest?: Partial<Config.InitialOptions>;
   scripts?: Record<string, string>;
+  type?: 'commonjs' | 'module';
 };