jest-utils: add a getter for process.domain

CHANGELOG.md

@@ -49,6 +49,7 @@
 - `[jest-snapshot]` [**BREAKING**] Distinguish empty string from internal snapshot not written ([#8898](https://github.com/facebook/jest/pull/8898))
 - `[jest-snapshot]` [**BREAKING**] Remove `report` method and throw matcher errors ([#9049](https://github.com/facebook/jest/pull/9049))
 - `[jest-transform]` Properly cache transformed files across tests ([#8890](https://github.com/facebook/jest/pull/8890))
+- `[jest-utils]` Allow querying process.domain ([#9136](https://github.com/facebook/jest/pull/9136))
 - `[jest-transform]` Don't fail the test suite when a generated source map is invalid ([#9058](https://github.com/facebook/jest/pull/9058))
 
 ### Chore & Maintenance

e2e/__tests__/createProcessObject.test.ts

@@ -0,0 +1,14 @@
+/**
+ * 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 runJest from '../runJest';
+
+test('allows retrieving the current domain', () => {
+  const result = runJest('create-process-object');
+
+  expect(result.exitCode).toBe(0);
+});

e2e/create-process-object/__tests__/createProcessObject.test.js

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+
+const domain = require('domain');
+
+test('allows retrieving the current domain', () => {
+  domain.create().run(() => {
+    expect(process.domain).not.toBeNull();
+  });
+});

e2e/create-process-object/package.json

@@ -0,0 +1,6 @@
+{
+  "jest": {
+    "testEnvironment": "node",
+    "globalSetup": "<rootDir>/setup.js"
+  }
+}

e2e/create-process-object/setup.js

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+
+// Jest creates a copy of the global 'process' object and uses it instead of the one provided by node.
+// Since 'require'-ing the 'domain' module has a side-effect that modifies "process" to make it work with domains,
+// 'domain' has to be required before Jest performs the copy, i.e. in the global-setup phase represented by this file.
+
+module.exports = () => {
+  require('domain');
+};

packages/jest-util/src/createProcessObject.ts

@@ -112,5 +112,17 @@ export default function() {
   newProcess.env = createProcessEnv();
   newProcess.send = () => {};
 
+  const domainPropertyDescriptor = Object.getOwnPropertyDescriptor(
+    newProcess,
+    'domain',
+  );
+  if (domainPropertyDescriptor && !domainPropertyDescriptor.enumerable) {
+    Object.defineProperty(newProcess, 'domain', {
+      get() {
+        return process.domain;
+      },
+    });
+  }
+
   return newProcess;
 }