feat(jest-config): supports Jest config file with .mts extension

CHANGELOG.md

@@ -8,6 +8,7 @@
 ## Features
 
 - `[jest-environment-jsdom-abstract]` Add support for JSDOM v27 ([#15834](https://github.com/jestjs/jest/pull/15834))
+- `[jest-config]` Supports Jest config file with `.mts` extension ([#15796](https://github.com/jestjs/jest/pull/15796))
 
 ### Fixes
 

e2e/__tests__/__snapshots__/jest.config.mts.test.ts.snap

@@ -0,0 +1,120 @@
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
+
+exports[`on node <20.19.0 does not work with jest.config.mts when require(esm) is not supported 1`] = `
+"Error: Jest: Failed to parse the TypeScript config file <<REPLACED>>
+    Current Node version <<REPLACED>> does not support loading .mts Jest config.
+    Please upgrade to ^20.19.0 || >=22.12.0"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 invalid JS in jest.config.mts (node with native TS support) 1`] = `
+"Error: Jest: Failed to parse the TypeScript config file <<REPLACED>>
+    both with the native node TypeScript support and configured TypeScript loaders.
+    Errors were:
+    - SyntaxError [ERR_INVALID_TYPESCRIPT_SYNTAX]:   x Expected ';', got 'string literal (ll break this file yo, 'll break this file yo)'
+   ,----
+ 1 | export default i'll break this file yo
+   :                 ^^^^^^^^^^^^^^^^^^^^^^
+   \`----
+  x Unterminated string constant
+   ,----
+ 1 | export default i'll break this file yo
+   :                 ^^^^^^^^^^^^^^^^^^^^^^
+   \`----
+
+    - TSError: ⨯ Unable to compile TypeScript:
+jest.config.mts(1,16): error TS2304: Cannot find name 'i'.
+jest.config.mts(1,17): error TS1005: ';' expected.
+jest.config.mts(1,39): error TS1002: Unterminated string literal."
+`;
+
+exports[`on node >=22.18.0 || ^23.6 traverses directory tree up until it finds jest.config 1`] = `
+"  console.log
+<<REPLACED>>/jest-config-ts/some/nested/directory
+
+      at Object.<anonymous> (__tests__/a-giraffe.js:3:27)
+"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 traverses directory tree up until it finds jest.config 2`] = `
+"PASS ../../../__tests__/a-giraffe.js
+  ✓ giraffe
+  ✓ abc"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 traverses directory tree up until it finds jest.config 3`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       2 passed, 2 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;
+
+exports[`on node >=22.18.0 || ^23.6 work with untyped jest.config.mts 1`] = `
+"PASS __tests__/a-giraffe.js
+  ✓ giraffe"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 work with untyped jest.config.mts 2`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;
+
+exports[`on node >=22.18.0 || ^23.6 works with tsconfig.json 1`] = `
+"PASS __tests__/a-giraffe.js
+  ✓ giraffe"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 works with tsconfig.json 2`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;
+
+exports[`on node >=22.18.0 || ^23.6 works with typed jest.config.mts 1`] = `
+"PASS __tests__/a-giraffe.js
+  ✓ giraffe"
+`;
+
+exports[`on node >=22.18.0 || ^23.6 works with typed jest.config.mts 2`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;
+
+exports[`on node >=24 invalid JS in jest.config.mts (node with native TS support) 1`] = `
+"Error: Jest: Failed to parse the TypeScript config file <<REPLACED>>
+    both with the native node TypeScript support and configured TypeScript loaders.
+    Errors were:
+    - SyntaxError [ERR_INVALID_TYPESCRIPT_SYNTAX]: Expected ';', got 'string literal (ll break this file yo, 'll break this file yo)'
+    - TSError: ⨯ Unable to compile TypeScript:
+jest.config.mts(1,16): error TS2304: Cannot find name 'i'.
+jest.config.mts(1,17): error TS1005: ';' expected.
+jest.config.mts(1,39): error TS1002: Unterminated string literal."
+`;
+
+exports[`on node ^20.19.0 || >=22.12.0 <22.18.0 || 23 - 23.6.0 does not work with typed jest.config.ts 1`] = `
+"Error: Jest: Failed to parse the TypeScript config file <<REPLACED>>
+    Current Node version <<REPLACED>> does not support loading typed .mts Jest config.
+    Please upgrade to >=22.18.0 || ^23.6
+    Error: SyntaxError: Missing initializer in const declaration"
+`;
+
+exports[`on node ^20.19.0 || >=22.12.0 <22.18.0 || 23 - 23.6.0 work with untyped jest.config.mts 1`] = `
+"PASS __tests__/a-giraffe.js
+  ✓ giraffe"
+`;
+
+exports[`on node ^20.19.0 || >=22.12.0 <22.18.0 || 23 - 23.6.0 work with untyped jest.config.mts 2`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;

e2e/__tests__/jest.config.mts.test.ts

@@ -0,0 +1,248 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as path from 'path';
+import {onNodeVersions} from '@jest/test-utils';
+import {cleanup, extractSummary, writeFiles} from '../Utils';
+import runJest from '../runJest';
+
+const DIR = path.resolve(__dirname, '../jest-config-ts');
+
+beforeEach(() => cleanup(DIR));
+afterAll(() => cleanup(DIR));
+
+onNodeVersions('<20.19.0', () => {
+  test('does not work with jest.config.mts when require(esm) is not supported', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts':
+        "export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    expect(
+      stderr
+        // Remove the stack trace from the error message
+        .slice(0, Math.max(0, stderr.indexOf('at readConfigFileAndSetRootDir')))
+        .trim()
+        // Replace the path to the config file with a placeholder
+        .replace(
+          /(Error: Jest: Failed to parse the TypeScript config file).*$/m,
+          '$1 <<REPLACED>>',
+        )
+        // Replace Node version with
+        .replace(/(Current Node version) (.+?) /m, '$1 <<REPLACED>> '),
+    ).toMatchSnapshot();
+    expect(exitCode).toBe(1);
+  });
+});
+
+onNodeVersions('^20.19.0 || >=22.12.0 <22.18.0 || 23 - 23.6.0', () => {
+  test('work with untyped jest.config.mts', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts':
+        "export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    const {rest, summary} = extractSummary(stderr);
+    expect(exitCode).toBe(0);
+    expect(rest).toMatchSnapshot();
+    expect(summary).toMatchSnapshot();
+  });
+
+  test('does not work with typed jest.config.ts', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts': `
+        import {Config} from 'jest';
+        const config: Config = {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js' };
+        export default config;
+      `,
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    expect(
+      stderr
+        // Remove the stack trace from the error message
+        .slice(0, Math.max(0, stderr.indexOf('at readConfigFileAndSetRootDir')))
+        .trim()
+        // Replace the path to the config file with a placeholder
+        .replace(
+          /(Error: Jest: Failed to parse the TypeScript config file).*$/m,
+          '$1 <<REPLACED>>',
+        )
+        // Replace Node version with
+        .replace(/(Current Node version) (.+?) /m, '$1 <<REPLACED>> '),
+    ).toMatchSnapshot();
+    expect(exitCode).toBe(1);
+  });
+
+  test('invalid JS in jest.config.mts', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts': "export default i'll break this file yo",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
+    expect(stderr).toMatch('SyntaxError: Invalid or unexpected token');
+    expect(exitCode).toBe(1);
+  });
+});
+
+onNodeVersions('>=22.18.0 || ^23.6', () => {
+  test('work with untyped jest.config.mts', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts':
+        "export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    const {rest, summary} = extractSummary(stderr);
+    expect(exitCode).toBe(0);
+    expect(rest).toMatchSnapshot();
+    expect(summary).toMatchSnapshot();
+  });
+
+  test('works with typed jest.config.mts', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts': `
+        import {Config} from 'jest';
+        const config: Config = {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js' };
+        export default config;
+      `,
+      'package.json': '{"type": "commonjs"}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    const {rest, summary} = extractSummary(stderr);
+    expect(exitCode).toBe(0);
+    expect(rest).toMatchSnapshot();
+    expect(summary).toMatchSnapshot();
+  });
+
+  test('works with tsconfig.json', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts':
+        "export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};",
+      'package.json': '{}',
+      'tsconfig.json': '{ "compilerOptions": { "module": "esnext" } }',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    const {rest, summary} = extractSummary(stderr);
+    expect(exitCode).toBe(0);
+    expect(rest).toMatchSnapshot();
+    expect(summary).toMatchSnapshot();
+  });
+
+  test('traverses directory tree up until it finds jest.config', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': `
+      const slash = require('slash');
+      test('giraffe', () => expect(1).toBe(1));
+      test('abc', () => console.log(slash(process.cwd())));
+      `,
+      'jest.config.mts':
+        "export default {testEnvironment: 'jest-environment-node', testRegex: '.*-giraffe.js'};",
+      'package.json': '{}',
+      'some/nested/directory/file.js': '// nothing special',
+    });
+
+    const {stderr, exitCode, stdout} = runJest(
+      path.join(DIR, 'some', 'nested', 'directory'),
+      ['-w=1', '--ci=false'],
+      {nodeOptions: '--no-warnings', skipPkgJsonCheck: true},
+    );
+
+    // Snapshot the console.logged `process.cwd()` and make sure it stays the same
+    expect(
+      stdout
+        .replaceAll(/^\W+(.*)e2e/gm, '<<REPLACED>>')
+        // slightly different log in node versions >= 23
+        .replace('at Object.log', 'at Object.<anonymous>'),
+    ).toMatchSnapshot();
+
+    const {rest, summary} = extractSummary(stderr);
+    expect(exitCode).toBe(0);
+    expect(rest).toMatchSnapshot();
+    expect(summary).toMatchSnapshot();
+  });
+
+  test('invalid JS in jest.config.mts (node with native TS support)', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts': "export default i'll break this file yo",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    expect(
+      stderr
+        // Remove the stack trace from the error message
+        .slice(0, Math.max(0, stderr.indexOf('at readConfigFileAndSetRootDir')))
+        .trim()
+        // Replace the path to the config file with a placeholder
+        .replace(
+          /(Error: Jest: Failed to parse the TypeScript config file).*$/m,
+          '$1 <<REPLACED>>',
+        ),
+    ).toMatchSnapshot();
+    expect(exitCode).toBe(1);
+  });
+});
+
+onNodeVersions('>=24', () => {
+  // todo fixme
+  // eslint-disable-next-line jest/no-identical-title
+  test('invalid JS in jest.config.mts (node with native TS support)', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.mts': "export default i'll break this file yo",
+      'package.json': '{}',
+    });
+
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+      nodeOptions: '--no-warnings',
+    });
+    expect(
+      stderr
+        // Remove the stack trace from the error message
+        .slice(0, Math.max(0, stderr.indexOf('at readConfigFileAndSetRootDir')))
+        .trim()
+        // Replace the path to the config file with a placeholder
+        .replace(
+          /(Error: Jest: Failed to parse the TypeScript config file).*$/m,
+          '$1 <<REPLACED>>',
+        ),
+    ).toMatchSnapshot();
+    expect(exitCode).toBe(1);
+  });
+});

packages/jest-config/package.json

@@ -57,6 +57,7 @@
     "micromatch": "^4.0.8",
     "parse-json": "^5.2.0",
     "pretty-format": "workspace:*",
+    "semver": "^7.7.2",
     "slash": "^3.0.0",
     "strip-json-comments": "^3.1.1"
   },
@@ -67,7 +68,6 @@
     "@types/parse-json": "^4.0.2",
     "esbuild": "^0.25.5",
     "esbuild-register": "^3.6.0",
-    "semver": "^7.7.2",
     "ts-node": "^10.5.0",
     "typescript": "^5.8.3"
   },