print stack trace on calls to process.exit (#6714)

* print stack trace on calls to process.exit

* link PR in changelog

* guard exit handler against missing global process

* moar guard

* remove unnecessary newline

Author: SimenB

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## master
 
+### Features
+
+- `[jest-runner]` print stack trace when `process.exit` is called from user code ([#6714](https://github.com/facebook/jest/pull/6714))
+
 ### Fixes
 
 - `[jest-snapshot` Mark snapshots as obsolete when moved to an inline snapshot ([#6773](https://github.com/facebook/jest/pull/6773))

e2e/__tests__/__snapshots__/process_exit.test.js.snap

@@ -0,0 +1,14 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`prints stack trace pointing to process.exit call 1`] = `
+"  ●  process.exit called with \\"1\\"
+
+    > 1 | process.exit(1);
+        |         ^
+      2 | 
+      3 | test('something', () => {
+      4 |   expect(true).toBe(true);
+
+      at Object.<anonymous> (__tests__/test.js:1:9)
+"
+`;

e2e/__tests__/process_exit.test.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @flow
+ */
+'use strict';
+
+const runJest = require('../runJest');
+
+it('prints stack trace pointing to process.exit call', async () => {
+  const {stderr} = await runJest('process-exit');
+
+  expect(stderr).toMatchSnapshot();
+});

e2e/process-exit/__tests__/test.js

@@ -0,0 +1,5 @@
+process.exit(1);
+
+test('something', () => {
+  expect(true).toBe(true);
+});

e2e/process-exit/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}

packages/jest-runner/src/run_test.js

@@ -25,6 +25,7 @@ import {
 import LeakDetector from 'jest-leak-detector';
 import {getTestEnvironment} from 'jest-config';
 import * as docblock from 'jest-docblock';
+import {formatExecError} from 'jest-message-util';
 import sourcemapSupport from 'source-map-support';
 
 type RunTestInternalResult = {
@@ -145,6 +146,34 @@ async function runTestInternal(
   // For runtime errors
   sourcemapSupport.install(sourcemapOptions);
 
+  if (
+    environment.global &&
+    environment.global.process &&
+    environment.global.process.exit
+  ) {
+    const realExit = environment.global.process.exit;
+
+    environment.global.process.exit = function exit(...args) {
+      const error = new Error(`process.exit called with "${args.join(', ')}"`);
+
+      if (Error.captureStackTrace) {
+        Error.captureStackTrace(error, exit);
+      }
+
+      const formattedError = formatExecError(
+        error,
+        config,
+        {noStackTrace: false},
+        undefined,
+        true,
+      );
+
+      process.stderr.write(formattedError);
+
+      return realExit(...args);
+    };
+  }
+
   try {
     await environment.setup();