fix(jest-runtime): Guard '_isMockFunction' access with 'in'

packages/jest-runtime/src/__tests__/runtime_resetModules_unsafe_global_proxy.js

@@ -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.
+ *
+ */
+
+'use strict';
+
+import NodeEnvironment from 'jest-environment-node';
+
+let createRuntime;
+
+describe('Runtime', () => {
+  beforeEach(() => {
+    createRuntime = require('createRuntime');
+  });
+
+  describe('resetModules', () => {
+    it('does not throw when accessing _isMockFunction on an unsafe global', async () => {
+      const runtime = await createRuntime(__filename);
+      runtime._environment.global.UNSAFE_GLOBAL = new Proxy(
+        {},
+        {
+          get(target, p, receiver) {
+            if (p === '_isMockFunction') throw new Error('Unsafe global!');
+          },
+        },
+      );
+      runtime.resetModules();
+    });
+  });
+});

packages/jest-runtime/src/index.ts

@@ -1218,6 +1218,7 @@ export default class Runtime {
             if (
               ((typeof globalMock === 'object' && globalMock !== null) ||
                 typeof globalMock === 'function') &&
+              '_isMockFunction' in globalMock &&
               globalMock._isMockFunction === true
             ) {
               globalMock.mockClear();