fix: repair caching of typescript compiler instances

CHANGELOG.md

@@ -9,6 +9,7 @@
 
 ### Fixes
 
+- `[jest-config]` Fix testing multiple projects with TypeScript config files ([#13099](https://github.com/facebook/jest/pull/13099))
 - `[@jest/expect-utils]` Fix deep equality of ImmutableJS Record ([#13055](https://github.com/facebook/jest/pull/13055))
 - `[jest-haste-map]` Increase the maximum possible file size that jest-haste-map can handle ([#13094](https://github.com/facebook/jest/pull/13094))
 - `[jest-worker]` When a process runs out of memory worker exits correctly and doesn't spin indefinitely ([#13054](https://github.com/facebook/jest/pull/13054))

e2e/__tests__/typescriptConfigFile.test.ts

@@ -0,0 +1,109 @@
+/**
+ * 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 {tmpdir} from 'os';
+import * as path from 'path';
+import {cleanup, writeFiles} from '../Utils';
+import runJest from '../runJest';
+
+const DIR = path.resolve(tmpdir(), 'typescript-config-file');
+
+beforeEach(() => cleanup(DIR));
+afterEach(() => cleanup(DIR));
+
+test('works with single typescript config that imports something', () => {
+  writeFiles(DIR, {
+    '__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';
+    export default {
+      testRegex: [ commonRegex, '__tests__/mytest.alpha.js' ]
+    };`,
+    'common.ts': "export default '__tests__/mytest.common.js$';",
+  });
+
+  const {stdout, stderr, exitCode} = runJest(
+    DIR,
+    ['--projects', 'alpha.config.ts'],
+    {
+      skipPkgJsonCheck: true,
+    },
+  );
+
+  expect(stderr).toContain('PASS __tests__/mytest.alpha.js');
+  expect(stderr).toContain('PASS __tests__/mytest.common.js');
+  expect(stderr).toContain('Test Suites: 2 passed, 2 total');
+  expect(exitCode).toBe(0);
+  expect(stdout).toBe('');
+});
+
+test('works with multiple typescript configs', () => {
+  writeFiles(DIR, {
+    '__tests__/mytest.alpha.js': "test('alpha', () => expect(1).toBe(1));",
+    '__tests__/mytest.beta.js': "test('beta', () => expect(1).toBe(1));",
+    'alpha.config.ts': `
+    export default {
+      testRegex: '__tests__/mytest.alpha.js'
+    };`,
+    'beta.config.ts': `
+    export default {
+      testRegex: '__tests__/mytest.beta.js'
+    };`,
+  });
+
+  const {stdout, stderr, exitCode} = runJest(
+    DIR,
+    ['--projects', 'alpha.config.ts', 'beta.config.ts'],
+    {
+      skipPkgJsonCheck: true,
+    },
+  );
+
+  expect(stderr).toContain('PASS __tests__/mytest.alpha.js');
+  expect(stderr).toContain('PASS __tests__/mytest.beta.js');
+  expect(stderr).toContain('Test Suites: 2 passed, 2 total');
+  expect(exitCode).toBe(0);
+  expect(stdout).toBe('');
+});
+
+test('works with multiple typescript configs that import something', () => {
+  writeFiles(DIR, {
+    '__tests__/mytest.alpha.js': "test('alpha', () => expect(1).toBe(1));",
+    '__tests__/mytest.beta.js': "test('beta', () => expect(1).toBe(1));",
+    '__tests__/mytest.common.js': "test('common', () => expect(1).toBe(1));",
+    'alpha.config.ts': `
+    import commonRegex from './common';
+    export default {
+      testRegex: [ commonRegex, '__tests__/mytest.alpha.js' ]
+    };`,
+    'beta.config.ts': `
+    import commonRegex from './common';
+    export default {
+      testRegex: [ commonRegex, '__tests__/mytest.beta.js' ]
+    };`,
+    'common.ts': "export default '__tests__/mytest.common.js$';",
+  });
+
+  const {stdout, stderr, exitCode} = runJest(
+    DIR,
+    ['--projects', 'alpha.config.ts', 'beta.config.ts'],
+    {
+      skipPkgJsonCheck: true,
+    },
+  );
+
+  expect(stderr).toContain('PASS __tests__/mytest.alpha.js');
+  expect(stderr).toContain('PASS __tests__/mytest.beta.js');
+  expect(stderr).toContain('PASS __tests__/mytest.common.js');
+  expect(stderr.replace('PASS __tests__/mytest.common.js', '')).toContain(
+    'PASS __tests__/mytest.common.js',
+  );
+  expect(stderr).toContain('Test Suites: 4 passed, 4 total');
+  expect(exitCode).toBe(0);
+  expect(stdout).toBe('');
+});

packages/jest-config/src/readConfigFileAndSetRootDir.ts

@@ -77,16 +77,14 @@ export default async function readConfigFileAndSetRootDir(
   return configObject;
 }
 
-let registerer: Service;
-
 // Load the TypeScript configuration
 const loadTSConfigFile = async (
   configPath: string,
 ): Promise<Config.InitialOptions> => {
-  // Register TypeScript compiler instance
-  await registerTsNode();
+  // Get registered TypeScript compiler instance
+  const registeredCompiler = await getRegisteredCompiler();
 
-  registerer.enabled(true);
+  registeredCompiler.enabled(true);
 
   let configObject = interopRequireDefault(require(configPath)).default;
 
@@ -95,27 +93,31 @@ const loadTSConfigFile = async (
     configObject = await configObject();
   }
 
-  registerer.enabled(false);
+  registeredCompiler.enabled(false);
 
   return configObject;
 };
 
-async function registerTsNode(): Promise<Service> {
-  if (registerer) {
-    return registerer;
-  }
+let registeredCompilerPromise: Promise<Service>;
 
+function getRegisteredCompiler() {
+  // Cache the promise to avoid multiple registrations
+  registeredCompilerPromise = registeredCompilerPromise ?? registerTsNode();
+  return registeredCompilerPromise;
+}
+
+async function registerTsNode(): Promise<Service> {
   try {
+    // Register TypeScript compiler instance
     const tsNode = await import('ts-node');
-    registerer = tsNode.register({
+    return tsNode.register({
       compilerOptions: {
         module: 'CommonJS',
       },
       moduleTypes: {
         '**': 'cjs',
       },
     });
-    return registerer;
   } catch (e: any) {
     if (e.code === 'ERR_MODULE_NOT_FOUND') {
       throw new Error(