fix(jest-runner): Handle unsafe worker_threads structureClone with function type in matchers

packages/jest-runner/src/__tests__/helpers.test.ts

@@ -0,0 +1,34 @@
+/**
+ * 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 {replaceFunctionsWithStringReferences} from '../helpers';
+
+it('serialize functions inside the nested object', () => {
+  const obj = {
+    foo: () => {},
+    nested: {
+      fn: function bar() {
+        return 0;
+      },
+    },
+    nestedArray: [{baz: function baz() {}}, () => {}],
+  };
+
+  expect(replaceFunctionsWithStringReferences(obj)).toEqual({
+    foo: '[Function foo]',
+    nested: {
+      fn: '[Function bar]',
+    },
+    nestedArray: [
+      {
+        baz: '[Function baz]',
+      },
+      '[Function anonymous]',
+    ],
+  });
+});

packages/jest-runner/src/helpers.ts

@@ -0,0 +1,29 @@
+/**
+ * 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.
+ */
+
+export const replaceFunctionsWithStringReferences = <T>(value: T): T => {
+  if (typeof value === 'function') {
+    return `[Function ${value.name || 'anonymous'}]` as unknown as T;
+  }
+
+  if (Array.isArray(value)) {
+    return value.map(replaceFunctionsWithStringReferences) as T;
+  }
+
+  const isObject = value !== null && typeof value === 'object';
+  if (isObject) {
+    const oldObject = value as Record<string, unknown>;
+    const newObject: Record<string, unknown> = {};
+    for (const key of Object.keys(value)) {
+      newObject[key] = replaceFunctionsWithStringReferences(oldObject[key]);
+    }
+
+    return newObject as T;
+  }
+
+  return value;
+};

packages/jest-runner/src/testWorker.ts

@@ -18,6 +18,7 @@ import {separateMessageFromStack} from 'jest-message-util';
 import type Resolver from 'jest-resolve';
 import Runtime from 'jest-runtime';
 import {messageParent} from 'jest-worker';
+import {replaceFunctionsWithStringReferences} from './helpers';
 import runTest from './runTest';
 import type {ErrorWithCode, TestRunnerSerializedContext} from './types';
 
@@ -96,7 +97,7 @@ export async function worker({
   context,
 }: WorkerData): Promise<TestResult> {
   try {
-    return await runTest(
+    const testResult = await runTest(
       path,
       globalConfig,
       config,
@@ -110,7 +111,28 @@ export async function worker({
       },
       sendMessageToJest,
     );
+    return makeSerializableTestResults(testResult);
   } catch (error: any) {
     throw formatError(error);
   }
 }
+
+function makeSerializableTestResults(result: TestResult): TestResult {
+  const {testResults} = result;
+  const serializableResults = testResults.map(resultItem => {
+    if (resultItem.failureDetails) {
+      return {
+        ...resultItem,
+        // Functions cause DataCloneError when passed between workers,
+        // therefore they are converted to string references
+        failureDetails: replaceFunctionsWithStringReferences(
+          resultItem.failureDetails,
+        ),
+      };
+    }
+
+    return resultItem;
+  });
+
+  return {...result, testResults: serializableResults};
+}