feat(config): if process.features.typescript is set, load `jest.con…

…fig.ts` without external loader (#15480) if `process.features.typescript` is set, load `jest.config.ts` without external loader see https://nodejs.org/api/process.html#processfeaturestypescript This value is set if node is run with `--experimental-transform-types` or `--experimental-strip-types` so no external package is required for transpilation in those cases
jestjs · Jan 30, 2025 · d336118 · d336118
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -15,7 +15,8 @@
 - `[jest-config]` Allow loading `jest.config.cts` files ([#14070](https://github.com/facebook/jest/pull/14070))
 - `[jest-config]` Show `rootDir` in error message when a `preset` fails to load ([#15194](https://github.com/jestjs/jest/pull/15194))
 - `[jest-config]` Support loading TS config files using `esbuild-register` via docblock loader ([#15190](https://github.com/jestjs/jest/pull/15190))
-- `[jest-config]` allow passing TS config loader options via docblock comment ([#15234](https://github.com/jestjs/jest/pull/15234))
+- `[jest-config]` Allow passing TS config loader options via docblock comment ([#15234](https://github.com/jestjs/jest/pull/15234))
+- `[jest-config]` If Node is running with type stripping enabled, do not require a TS loader ([#15480](https://github.com/jestjs/jest/pull/15480))
 - `[@jest/core]` Group together open handles with the same stack trace ([#13417](https://github.com/jestjs/jest/pull/13417), & [#14789](https://github.com/jestjs/jest/pull/14789))
 - `[@jest/core]` Add `perfStats` to surface test setup overhead ([#14622](https://github.com/jestjs/jest/pull/14622))
 - `[@jest/core]` [**BREAKING**] Changed `--filter` to accept an object with shape `{ filtered: Array<string> }` to match [documentation](https://jestjs.io/docs/cli#--filterfile) ([#13319](https://github.com/jestjs/jest/pull/13319))

diff --git a/e2e/__tests__/__snapshots__/jest.config.ts.test.ts.snap b/e2e/__tests__/__snapshots__/jest.config.ts.test.ts.snap
@@ -1,5 +1,19 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`on node >=23.6 invalid JS in jest.config.ts (node with native TS support) 1`] = `
+"Error: Jest: Failed to parse the TypeScript config file <<REPLACED>>
+  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
+   :                 ^^^^^^^^^^^^^^^^^^^^^^
+   \`----"
+`;
+
 exports[`traverses directory tree up until it finds jest.config 1`] = `
 "  console.log
 <<REPLACED>>/jest-config-ts/some/nested/directory

diff --git a/e2e/__tests__/jest.config.ts.test.ts b/e2e/__tests__/jest.config.ts.test.ts
@@ -7,6 +7,7 @@
 
 import * as path from 'path';
 import * as fs from 'graceful-fs';
+import {onNodeVersions} from '@jest/test-utils';
 import {cleanup, extractSummary, writeFiles} from '../Utils';
 import runJest from '../runJest';
 
@@ -23,7 +24,9 @@ test('works with jest.config.ts', () => {
     'package.json': '{}',
   });
 
-  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
+  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+    nodeOptions: '--no-warnings',
+  });
   const {rest, summary} = extractSummary(stderr);
   expect(exitCode).toBe(0);
   expect(rest).toMatchSnapshot();
@@ -39,7 +42,9 @@ test('works with tsconfig.json', () => {
     'tsconfig.json': '{ "compilerOptions": { "module": "esnext" } }',
   });
 
-  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
+  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false'], {
+    nodeOptions: '--no-warnings',
+  });
   const {rest, summary} = extractSummary(stderr);
   expect(exitCode).toBe(0);
   expect(rest).toMatchSnapshot();
@@ -62,62 +67,95 @@ test('traverses directory tree up until it finds jest.config', () => {
   const {stderr, exitCode, stdout} = runJest(
     path.join(DIR, 'some', 'nested', 'directory'),
     ['-w=1', '--ci=false'],
-    {skipPkgJsonCheck: true},
+    {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>>')).toMatchSnapshot();
+  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();
 });
 
-const jestPath = require.resolve('jest');
-const jestTypesPath = jestPath.replace(/\.js$/, '.d.ts');
-const jestTypesExists = fs.existsSync(jestTypesPath);
+onNodeVersions('<23.6', () => {
+  const jestPath = require.resolve('jest');
+  const jestTypesPath = jestPath.replace(/\.js$/, '.d.ts');
+  const jestTypesExists = fs.existsSync(jestTypesPath);
+
+  (jestTypesExists ? test : test.skip).each([true, false])(
+    'check the config disabled (skip type check: %p)',
+    skipTypeCheck => {
+      writeFiles(DIR, {
+        '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+        'jest.config.ts': `
+        /**@jest-config-loader-options {"transpileOnly":${!!skipTypeCheck}}*/
+        import {Config} from 'jest';
+        const config: Config = { testTimeout: "10000" };
+        export default config;
+      `,
+        'package.json': '{}',
+      });
+
+      const typeErrorString =
+        "TS2322: Type 'string' is not assignable to type 'number'.";
+      const runtimeErrorString = 'Option "testTimeout" must be of type:';
+
+      const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
+
+      if (skipTypeCheck) {
+        expect(stderr).not.toMatch(typeErrorString);
+        expect(stderr).toMatch(runtimeErrorString);
+      } else {
+        expect(stderr).toMatch(typeErrorString);
+        expect(stderr).not.toMatch(runtimeErrorString);
+      }
+
+      expect(exitCode).toBe(1);
+    },
+  );
 
-(jestTypesExists ? test : test.skip).each([true, false])(
-  'check the config disabled (skip type check: %p)',
-  skipTypeCheck => {
+  test('invalid JS in jest.config.ts', () => {
     writeFiles(DIR, {
       '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
-      'jest.config.ts': `
-      /**@jest-config-loader-options {"transpileOnly":${!!skipTypeCheck}}*/
-      import {Config} from 'jest';
-      const config: Config = { testTimeout: "10000" };
-      export default config;
-    `,
+      'jest.config.ts': "export default i'll break this file yo",
       'package.json': '{}',
     });
 
-    const typeErrorString =
-      "TS2322: Type 'string' is not assignable to type 'number'.";
-    const runtimeErrorString = 'Option "testTimeout" must be of type:';
-
     const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
+    expect(stderr).toMatch('TSError: ⨯ Unable to compile TypeScript:');
+    expect(exitCode).toBe(1);
+  });
+});
 
-    if (skipTypeCheck) {
-      expect(stderr).not.toMatch(typeErrorString);
-      expect(stderr).toMatch(runtimeErrorString);
-    } else {
-      expect(stderr).toMatch(typeErrorString);
-      expect(stderr).not.toMatch(runtimeErrorString);
-    }
+onNodeVersions('>=23.6', () => {
+  test('invalid JS in jest.config.ts (node with native TS support)', () => {
+    writeFiles(DIR, {
+      '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
+      'jest.config.ts': "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('Caused by')))
+        .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);
-  },
-);
-
-test('invalid JS in jest.config.ts', () => {
-  writeFiles(DIR, {
-    '__tests__/a-giraffe.js': "test('giraffe', () => expect(1).toBe(1));",
-    'jest.config.ts': "export default i'll break this file yo",
-    'package.json': '{}',
   });
-
-  const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false']);
-  expect(stderr).toMatch('TSError: ⨯ Unable to compile TypeScript:');
-  expect(exitCode).toBe(1);
 });
diff --git a/e2e/__tests__/readInitialOptions.test.ts b/e2e/__tests__/readInitialOptions.test.ts
@@ -6,6 +6,7 @@
  */
 import path = require('path');
 import execa = require('execa');
+import {onNodeVersions} from '@jest/test-utils';
 import type {ReadJestConfigOptions, readInitialOptions} from 'jest-config';
 
 function resolveFixture(...pathSegments: Array<string>) {
@@ -88,14 +89,16 @@ describe('readInitialOptions', () => {
     expect(configPath).toEqual(expectedConfigFile);
   });
 
-  test('should give an error when using unsupported loader', async () => {
-    const cwd = resolveFixture('ts-loader-config');
-    const error: Error = await proxyReadInitialOptions(undefined, {cwd}).catch(
-      error => error,
-    );
-    expect(error.message).toContain(
-      "Jest: 'ts-loader' is not a valid TypeScript configuration loader.",
-    );
+  onNodeVersions('<22.6', () => {
+    test('should give an error when using unsupported loader', async () => {
+      const cwd = resolveFixture('ts-loader-config');
+      const error: Error = await proxyReadInitialOptions(undefined, {
+        cwd,
+      }).catch(error => error);
+      expect(error.message).toContain(
+        "Jest: 'ts-loader' is not a valid TypeScript configuration loader.",
+      );
+    });
   });
 
   test('should give an error when there are multiple config files', async () => {

diff --git a/e2e/__tests__/typescriptConfigFile.test.ts b/e2e/__tests__/typescriptConfigFile.test.ts
@@ -7,10 +7,14 @@
 
 import {tmpdir} from 'os';
 import * as path from 'path';
+import * as semver from 'semver';
+import {onNodeVersions} from '@jest/test-utils';
 import {cleanup, writeFiles} from '../Utils';
 import runJest, {getConfig} from '../runJest';
 
 const DIR = path.resolve(tmpdir(), 'typescript-config-file');
+const useNativeTypeScript = semver.satisfies(process.versions.node, '>=23.6.0');
+const importFileExtension = useNativeTypeScript ? '.ts' : '';
 
 beforeEach(() => cleanup(DIR));
 afterEach(() => cleanup(DIR));
@@ -20,7 +24,7 @@ test('works with single typescript config that imports something', () => {
     '__tests__/mytest.alpha.js': "test('alpha', () => expect(1).toBe(1));",
     '__tests__/mytest.common.js': "test('common', () => expect(1).toBe(1));",
     'alpha.config.ts': `
-    import commonRegex from './common';
+    import commonRegex from './common${importFileExtension}';
     export default {
       testRegex: [ commonRegex, '__tests__/mytest.alpha.js' ]
     };`,
@@ -77,12 +81,12 @@ test('works with multiple typescript configs that import something', () => {
     '__tests__/mytest.beta.js': "test('beta', () => expect(1).toBe(1));",
     '__tests__/mytest.common.js': "test('common', () => expect(1).toBe(1));",
     'alpha.config.ts': `
-    import commonRegex from './common';
+    import commonRegex from './common${importFileExtension}';
     export default {
       testRegex: [ commonRegex, '__tests__/mytest.alpha.js' ]
     };`,
     'beta.config.ts': `
-    import commonRegex from './common';
+    import commonRegex from './common${importFileExtension}';
     export default {
       testRegex: [ commonRegex, '__tests__/mytest.beta.js' ]
     };`,
@@ -108,18 +112,20 @@ test('works with multiple typescript configs that import something', () => {
   expect(stdout).toBe('');
 });
 
-test("works with single typescript config that does not import anything with project's moduleResolution set to Node16", () => {
-  const {configs} = getConfig(
-    'typescript-config/modern-module-resolution',
-    [],
-    {
-      skipPkgJsonCheck: true,
-    },
-  );
+onNodeVersions('<23.6', () => {
+  test("works with single typescript config that does not import anything with project's moduleResolution set to Node16", () => {
+    const {configs} = getConfig(
+      'typescript-config/modern-module-resolution',
+      [],
+      {
+        skipPkgJsonCheck: true,
+      },
+    );
 
-  expect(configs).toHaveLength(1);
-  expect(configs[0].displayName).toEqual({
-    color: 'white',
-    name: 'Config from modern ts file',
+    expect(configs).toHaveLength(1);
+    expect(configs[0].displayName).toEqual({
+      color: 'white',
+      name: 'Config from modern ts file',
+    });
   });
 });
diff --git a/packages/jest-config/src/readConfigFileAndSetRootDir.ts b/packages/jest-config/src/readConfigFileAndSetRootDir.ts
@@ -36,10 +36,14 @@ export default async function readConfigFileAndSetRootDir(
     configPath.endsWith(JEST_CONFIG_EXT_TS) ||
     configPath.endsWith(JEST_CONFIG_EXT_CTS);
   const isJSON = configPath.endsWith(JEST_CONFIG_EXT_JSON);
+  // type assertion can be removed once @types/node is updated
+  // https://nodejs.org/api/process.html#processfeaturestypescript
+  const supportsTS = (process.features as {typescript?: boolean | string})
+    .typescript;
   let configObject;
 
   try {
-    if (isTS) {
+    if (isTS && !supportsTS) {
       configObject = await loadTSConfigFile(configPath);
     } else if (isJSON) {
       const fileContent = fs.readFileSync(configPath, 'utf8');