fix(jest-config): handle frozen config object

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixes
 
+- `[jest-config]` Handle frozen config object ([#14054](https://github.com/facebook/jest/pull/14054))
 - `[jest-environment-jsdom, jest-environment-node]` Fix assignment of `customExportConditions` via `testEnvironmentOptions` when custom env subclass defines a default value ([#13989](https://github.com/facebook/jest/pull/13989))
 - `[jest-matcher-utils]` Fix copying value of inherited getters ([#14007](https://github.com/facebook/jest/pull/14007))
 - `[jest-snapshot]` Fix a potential bug when not using prettier and improve performance ([#14036](https://github.com/facebook/jest/pull/14036))

packages/jest-config/src/__tests__/readConfigFileAndSetRootDir.test.ts

@@ -0,0 +1,169 @@
+/**
+ * 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 path = require('path');
+import * as fs from 'graceful-fs';
+import {requireOrImportModule} from 'jest-util';
+import readConfigFileAndSetRootDir from '../readConfigFileAndSetRootDir';
+
+jest.mock('graceful-fs').mock('jest-util');
+
+describe('readConfigFileAndSetRootDir', () => {
+  describe('JavaScript file', () => {
+    test('reads config and sets `rootDir`', async () => {
+      jest.mocked(requireOrImportModule).mockResolvedValueOnce({notify: true});
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.js'),
+      );
+
+      expect(config).toEqual({notify: true, rootDir});
+    });
+
+    test('handles exported function', async () => {
+      jest
+        .mocked(requireOrImportModule)
+        .mockResolvedValueOnce(() => ({bail: 1}));
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.js'),
+      );
+
+      expect(config).toEqual({bail: 1, rootDir});
+    });
+
+    test('handles exported async function', async () => {
+      jest
+        .mocked(requireOrImportModule)
+        .mockResolvedValueOnce(async () => ({testTimeout: 10000}));
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.js'),
+      );
+
+      expect(config).toEqual({rootDir, testTimeout: 10000});
+    });
+  });
+
+  describe('JSON file', () => {
+    test('reads config and sets `rootDir`', async () => {
+      jest.mocked(fs.readFileSync).mockReturnValueOnce('{ "verbose": true }');
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.json'),
+      );
+
+      expect(config).toEqual({rootDir, verbose: true});
+    });
+
+    test('supports comments in JSON', async () => {
+      jest
+        .mocked(fs.readFileSync)
+        .mockReturnValueOnce('{ // test comment\n "bail": true }');
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.json'),
+      );
+
+      expect(config).toEqual({bail: true, rootDir});
+    });
+  });
+
+  describe('package.json file', () => {
+    test('reads config from "jest" key and sets `rootDir`', async () => {
+      jest
+        .mocked(fs.readFileSync)
+        .mockReturnValueOnce('{ "jest": { "coverage": true } }');
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'package.json'),
+      );
+
+      expect(config).toEqual({coverage: true, rootDir});
+    });
+
+    test('sets rootDir if "jest" is absent', async () => {
+      jest.mocked(fs.readFileSync).mockReturnValueOnce('{ "name": "test" }');
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'package.json'),
+      );
+
+      expect(config).toEqual({rootDir});
+    });
+  });
+
+  describe('sets `rootDir`', () => {
+    test('handles frozen config object', async () => {
+      jest
+        .mocked(requireOrImportModule)
+        .mockResolvedValueOnce(Object.freeze({preset: 'some-preset'}));
+
+      const rootDir = path.resolve('some', 'path', 'to');
+      const config = await readConfigFileAndSetRootDir(
+        path.join(rootDir, 'jest.config.js'),
+      );
+
+      expect(config).toEqual({preset: 'some-preset', rootDir});
+    });
+
+    test('keeps the path if it is absolute', async () => {
+      const rootDir = path.resolve('some', 'path', 'to');
+      jest.mocked(requireOrImportModule).mockResolvedValueOnce({
+        rootDir,
+        testEnvironment: 'node',
+      });
+
+      const config = await readConfigFileAndSetRootDir(
+        path.join(path.resolve('other', 'path', 'to'), 'jest.config.js'),
+      );
+
+      expect(config).toEqual({rootDir, testEnvironment: 'node'});
+    });
+
+    test('resolves the path relative to dirname of the config file', async () => {
+      jest.mocked(requireOrImportModule).mockResolvedValueOnce({
+        restoreMocks: true,
+        rootDir: path.join('path', 'to'),
+      });
+
+      const config = await readConfigFileAndSetRootDir(
+        path.join(path.resolve('some'), 'jest.config.js'),
+      );
+
+      expect(config).toEqual({
+        restoreMocks: true,
+        rootDir: path.resolve('some', 'path', 'to'),
+      });
+    });
+
+    test('resolves relative path when the read config object if frozen', async () => {
+      jest.mocked(requireOrImportModule).mockResolvedValueOnce(
+        Object.freeze({
+          resetModules: true,
+          rootDir: path.join('path', 'to'),
+        }),
+      );
+
+      const config = await readConfigFileAndSetRootDir(
+        path.join(path.resolve('some'), 'jest.config.js'),
+      );
+
+      expect(config).toEqual({
+        resetModules: true,
+        rootDir: path.resolve('some', 'path', 'to'),
+      });
+    });
+  });
+});

packages/jest-config/src/readConfigFileAndSetRootDir.ts

@@ -64,14 +64,17 @@ export default async function readConfigFileAndSetRootDir(
     // We don't touch it if it has an absolute path specified
     if (!path.isAbsolute(configObject.rootDir)) {
       // otherwise, we'll resolve it relative to the file's __dirname
-      configObject.rootDir = path.resolve(
-        path.dirname(configPath),
-        configObject.rootDir,
-      );
+      configObject = {
+        ...configObject,
+        rootDir: path.resolve(path.dirname(configPath), configObject.rootDir),
+      };
     }
   } else {
     // If rootDir is not there, we'll set it to this file's __dirname
-    configObject.rootDir = path.dirname(configPath);
+    configObject = {
+      ...configObject,
+      rootDir: path.dirname(configPath),
+    };
   }
 
   return configObject;