fix(cli): .cjs files support by "--config" option

CHANGELOG.md

@@ -14,6 +14,7 @@
 - `[jest-config]` Support `.mjs` config files on Windows as well ([#9558](https://github.com/facebook/jest/pull/9558))
 - `[jest-config]` Verify `rootDir` and all `roots` are directories ([#9569](https://github.com/facebook/jest/pull/9569))
 - `[jest-cli]` Set `coverageProvider` correctly when provided in config ([#9562](https://github.com/facebook/jest/pull/9562))
+- `[jest-cli]` Allow specifying `.cjs` and `.mjs` config files by `--config` CLI option ([#9578](https://github.com/facebook/jest/pull/9578))
 - `[jest-config]` Ensure pattern of `replacePosixSep` is a string ([#9546]https://github.com/facebook/jest/pull/9546)
 - `[jest-matcher-utils]` Fix diff highlight of symbol-keyed object. ([#9499](https://github.com/facebook/jest/pull/9499))
 - `[@jest/reporters]` Notifications should be fire&forget rather than having a timeout ([#9567](https://github.com/facebook/jest/pull/9567))

packages/jest-cli/src/__tests__/cli/args.test.ts

@@ -7,6 +7,7 @@
  */
 
 import {Config} from '@jest/types';
+import {constants} from 'jest-config';
 import {check} from '../../cli/args';
 import {buildArgv} from '../../cli';
 
@@ -59,10 +60,34 @@ describe('check', () => {
     expect(() => check(argv)).not.toThrow();
   });
 
+  test.each(constants.JEST_CONFIG_EXT_ORDER.map(e => e.substring(1)))(
+    'allows using "%s" file for --config option',
+    ext => {
+      expect(() =>
+        check({config: `jest.config.${ext}`} as Config.Argv),
+      ).not.toThrow();
+      expect(() =>
+        check({config: `../test/test/my_conf.${ext}`} as Config.Argv),
+      ).not.toThrow();
+    },
+  );
+
   it('raises an exception if config is not a valid JSON string', () => {
     const argv = {config: 'x:1'} as Config.Argv;
     expect(() => check(argv)).toThrow(
-      'The --config option requires a JSON string literal, or a file path with a .js or .json extension',
+      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .mjs, .cjs, .json',
+    );
+  });
+
+  it('raises an exception if config is not a supported file type', () => {
+    const message =
+      'The --config option requires a JSON string literal, or a file path with one of these extensions: .js, .mjs, .cjs, .json';
+
+    expect(() => check({config: 'jest.configjs'} as Config.Argv)).toThrow(
+      message,
+    );
+    expect(() => check({config: 'jest.config.exe'} as Config.Argv)).toThrow(
+      message,
     );
   });
 });

packages/jest-cli/src/cli/args.ts

@@ -6,7 +6,7 @@
  */
 
 import {Config} from '@jest/types';
-import {isJSONString} from 'jest-config';
+import {constants, isJSONString} from 'jest-config';
 import isCI = require('is-ci');
 
 export function check(argv: Config.Argv): true {
@@ -52,11 +52,19 @@ export function check(argv: Config.Argv): true {
   if (
     argv.config &&
     !isJSONString(argv.config) &&
-    !argv.config.match(/\.js(on)?$/)
+    !argv.config.match(
+      new RegExp(
+        `\\.(${constants.JEST_CONFIG_EXT_ORDER.map(e => e.substring(1)).join(
+          '|',
+        )})$`,
+        'i',
+      ),
+    )
   ) {
     throw new Error(
-      'The --config option requires a JSON string literal, or a file path with a .js or .json extension.\n' +
-        'Example usage: jest --config ./jest.config.js',
+      `The --config option requires a JSON string literal, or a file path with one of these extensions: ${constants.JEST_CONFIG_EXT_ORDER.join(
+        ', ',
+      )}.\nExample usage: jest --config ./jest.config.js`,
     );
   }