Force redirecting stdout to stderr if useStderr is passed

e2e/__tests__/useStderr.test.ts

@@ -13,26 +13,58 @@ import {cleanup, writeFiles} from '../Utils';
 const DIR = path.resolve(os.tmpdir(), 'use-stderr-test');
 
 beforeEach(() => cleanup(DIR));
-afterEach(() => cleanup(DIR));
+afterAll(() => cleanup(DIR));
+
+const NUMBER_OF_TESTS_TO_FORCE_USING_WORKERS = 25;
+
+function runTest(useStderr: boolean, forceWorkers: boolean) {
+  const additionalTests = {};
+
+  if (forceWorkers) {
+    for (let i = 0; i < NUMBER_OF_TESTS_TO_FORCE_USING_WORKERS; i++) {
+      additionalTests[
+        `__tests__/test${i}.test.js`
+      ] = `test('test ${i}', () => {});`;
+    }
+  }
 
-test('no tests found message is redirected to stderr', () => {
   writeFiles(DIR, {
+    ...additionalTests,
+    '__tests__/test.test.js': `
+      require('../file1');
+      test('file1', () => {
+        console.log('Hello from console');
+        process.stdout.write('Hello from stdout\\n');
+        process.stderr.write('Hello from stderr\\n');
+      });
+    `,
     '.watchmanconfig': '',
     'file1.js': 'module.exports = {}',
     'package.json': JSON.stringify({jest: {testEnvironment: 'node'}}),
   });
-  let stderr;
-  let stdout;
 
-  ({stdout, stderr} = runJest(DIR, ['--useStderr']));
-  expect(stdout).toBe('');
-  expect(stderr).toMatch('No tests found');
+  const {stdout, stderr} = runJest(DIR, [
+    '--verbose',
+    useStderr ? '--useStderr' : '',
+    forceWorkers ? '--maxWorkers=2' : '--runInBand',
+  ]);
 
-  writeFiles(DIR, {
-    '__tests__/test.test.js': `require('../file1'); test('file1', () => {});`,
-  });
+  if (useStderr) {
+    expect(stdout).toBe('');
+  }
 
-  ({stdout, stderr} = runJest(DIR, ['--useStderr']));
-  expect(stdout).toBe('');
+  const generalOutput = useStderr ? stderr : stdout;
+  expect(generalOutput).toContain('Hello from stdout');
+  expect(generalOutput).toContain('Hello from console');
   expect(stderr).toMatch(/PASS.*test\.test\.js/);
+  expect(stderr).toContain('Hello from stderr');
+}
+
+test.each([
+  [true, 'in band'],
+  [false, 'in band'],
+  [true, 'with workers'],
+  [false, 'with workers'],
+])('passes when useStderr is %s, running %s', (useStderr, runMode) => {
+  runTest(useStderr, runMode === 'with workers');
 });

packages/jest-runner/src/index.ts

@@ -110,8 +110,14 @@ class TestRunner {
       numWorkers: this._globalConfig.maxWorkers,
     }) as WorkerInterface;
 
-    if (worker.getStdout()) worker.getStdout().pipe(process.stdout);
-    if (worker.getStderr()) worker.getStderr().pipe(process.stderr);
+    if (worker.getStdout()) {
+      worker
+        .getStdout()
+        .pipe(this._globalConfig.useStderr ? process.stderr : process.stdout);
+    }
+    if (worker.getStderr()) {
+      worker.getStderr().pipe(process.stderr);
+    }
 
     const mutex = throat(this._globalConfig.maxWorkers);
 

packages/jest-runner/src/runTest.ts

@@ -194,31 +194,41 @@ 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;
+  const globalProcess = environment.global && environment.global.process;
+
+  if (globalProcess) {
+    if (globalProcess.exit) {
+      const realExit = environment.global.process.exit;
+
+      environment.global.process.exit = function exit(...args: Array<any>) {
+        const error = new ErrorWithStack(
+          `process.exit called with "${args.join(', ')}"`,
+          exit,
+        );
+
+        const formattedError = formatExecError(
+          error,
+          config,
+          {noStackTrace: false},
+          undefined,
+          true,
+        );
+
+        process.stderr.write(formattedError);
+
+        return realExit(...args);
+      };
+    }
 
-    environment.global.process.exit = function exit(...args: Array<any>) {
-      const error = new ErrorWithStack(
-        `process.exit called with "${args.join(', ')}"`,
-        exit,
-      );
+    if (globalProcess.stderr) {
+      globalProcess.stderr.pipe(process.stderr);
+    }
 
-      const formattedError = formatExecError(
-        error,
-        config,
-        {noStackTrace: false},
-        undefined,
-        true,
+    if (globalProcess.stdout) {
+      globalProcess.stdout.pipe(
+        globalConfig.useStderr ? process.stderr : process.stdout,
       );
-
-      process.stderr.write(formattedError);
-
-      return realExit(...args);
-    };
+    }
   }
 
   try {

packages/jest-util/src/createProcessObject.ts

@@ -5,6 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import {PassThrough} from 'stream';
 import deepCyclicCopy from './deepCyclicCopy';
 
 const BLACKLIST = new Set(['env', 'mainModule', '_events']);
@@ -68,6 +69,18 @@ function createProcessEnv(): NodeJS.ProcessEnv {
   return Object.assign(proxy, process.env);
 }
 
+function overrideProcessStream(
+  newProcess: NodeJS.Process,
+  streamName: 'stdout' | 'stderr',
+) {
+  const newStream = new PassThrough();
+  Object.defineProperty(newProcess, streamName, {
+    ...Object.getOwnPropertyDescriptor(newProcess, streamName),
+    get: () => newStream,
+  });
+  newProcess[streamName].isTTY = newProcess[streamName].isTTY;
+}
+
 export default function() {
   const process = require('process');
   const newProcess = deepCyclicCopy(process, {
@@ -101,5 +114,8 @@ export default function() {
   newProcess.env = createProcessEnv();
   newProcess.send = () => {};
 
+  overrideProcessStream(newProcess, 'stdout');
+  overrideProcessStream(newProcess, 'stderr');
+
   return newProcess;
 }