safe --json && --listTests

integration_tests/__tests__/__snapshots__/show_config.test.js.snap

@@ -75,7 +75,6 @@ exports[`--showConfig outputs config info and exits 1`] = `
     \\"testPathPattern\\": \\"\\",
     \\"testResultsProcessor\\": null,
     \\"updateSnapshot\\": \\"all\\",
-    \\"useStderr\\": false,
     \\"verbose\\": null,
     \\"watch\\": false,
     \\"watchman\\": true

integration_tests/__tests__/custom_reporters.test.js

@@ -125,9 +125,8 @@ describe('Custom Reporters Integration', () => {
     ]);
 
     expect(status).toBe(0);
-    expect(stderr.trim()).toBe('');
-
     expect(stdout).toMatchSnapshot();
+    expect(stderr.trim()).toBe('');
   });
 
   test('prints reporter errors', () => {

integration_tests/__tests__/json_stdout.test.js

@@ -0,0 +1,93 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ */
+
+'use strict';
+
+const path = require('path');
+const os = require('os');
+const skipOnWindows = require('../../scripts/skip_on_windows');
+const {cleanup, writeFiles} = require('../utils');
+const runJest = require('../runJest');
+
+const DIR = path.resolve(os.tmpdir(), 'json_stdout_test');
+
+skipOnWindows.suite();
+
+beforeEach(() => cleanup(DIR));
+afterAll(() => cleanup(DIR));
+
+const reporterCode = `
+'use strict';
+
+console.log('at require time');
+console.log(console.log.toString());
+module.exports = class Reporter {
+  onRunStart() {
+    console.log('at runtime');
+  }
+};
+`;
+
+test('does not pollute stdout from third party code (or any code)', () => {
+  writeFiles(DIR, {
+    '.watchmanconfig': '',
+    '__tests__/hey.test.js': `test('test', () => {})`,
+    'custom_reporter.js': reporterCode,
+    'package.json': JSON.stringify({
+      jest: {
+        // Reporter will be required as a regular module in the master process
+        // before any of the test run, which makes it a perfect place to try
+        // to break the stdout by console.logging some text.
+        reporters: ['<rootDir>/custom_reporter.js', 'default'],
+      },
+    }),
+  });
+
+  let stdout;
+  let stderr;
+  ({stdout, stderr} = runJest(DIR, ['--json']));
+  expect(stdout).not.toMatch('at require time');
+  expect(stdout).not.toMatch('at runtime');
+  expect(stderr).toMatch('at require time');
+  expect(stderr).toMatch('at runtime');
+  expect(() => JSON.parse(stdout)).not.toThrow();
+
+  ({stdout, stderr} = runJest(DIR, ['--listTests', '__tests__/hey.test.js']));
+
+  expect(stdout).not.toMatch('at require time');
+  expect(stdout).not.toMatch('at runtime');
+  expect(stderr).not.toMatch('at require time');
+  expect(stderr).not.toMatch('at runtime');
+  expect(() => JSON.parse(stdout)).not.toThrow();
+  expect(stdout).toMatch('hey.test.js');
+});
+
+test('prints to stdout if not in json mode', () => {
+  writeFiles(DIR, {
+    '.watchmanconfig': '',
+    '__tests__/hey.test.js': `test('test', () => {})`,
+    'custom_reporter.js': reporterCode,
+    'package.json': JSON.stringify({
+      jest: {
+        // Reporter will be required as a regular module in the master process
+        // before any of the test run, which makes it a perfect place to try
+        // to break the stdout by console.logging some text.
+        reporters: ['<rootDir>/custom_reporter.js', 'default'],
+      },
+    }),
+  });
+
+  const {status, stdout, stderr} = runJest(DIR);
+  expect(stderr).not.toMatch('at runtime');
+  expect(stderr).not.toMatch('at require time');
+  expect(stdout).toMatch('at require time');
+  expect(stdout).toMatch('at runtime');
+  expect(status).toBe(0);
+});

packages/jest-cli/bin/jest.js

@@ -11,4 +11,9 @@ if (process.env.NODE_ENV == null) {
   process.env.NODE_ENV = 'test';
 }
 
-require('../build/cli').run();
+const stdout = process.stdout;
+// Prevent any code from printing to stdout because it will break JSON
+// output if we run jest with `--json` or `--listTests` flags.
+Object.defineProperty(process, 'stdout', {value: process.stderr});
+
+require('../build/cli').run(undefined, undefined, stdout);

packages/jest-cli/src/__tests__/__snapshots__/watch_test_name_pattern_mode.test.js.snap

@@ -20,7 +20,7 @@ exports[`Watch mode flows Pressing "T" enters pattern mode 1`] = `
 
  › should recognize null and undefined
 
- › should not output colors to pipe
+ › should not output colors to outputStream
 
  › should convert string to a RegExp
 
@@ -49,7 +49,7 @@ exports[`Watch mode flows Pressing "T" enters pattern mode 2`] = `
 
  › should recognize null and undefined
 
- › should not output colors to pipe
+ › should not output colors to outputStream
 
  › should convert string to a RegExp
 
@@ -187,7 +187,7 @@ exports[`Watch mode flows Results in pattern mode get truncated appropriately 1`
 
  › should recognize various types
 
- › should not output colors to pipe
+ › should not output colors to outputStream
 
  › should convert string to a RegExp
 

packages/jest-cli/src/__tests__/watch.test.js

@@ -36,15 +36,15 @@ const watch = require('../watch');
 afterEach(runJestMock.mockReset);
 
 describe('Watch mode flows', () => {
-  let pipe;
+  let outputStream;
   let hasteMapInstances;
   let globalConfig;
   let contexts;
   let stdin;
 
   beforeEach(() => {
     const config = {roots: [], testPathIgnorePatterns: [], testRegex: ''};
-    pipe = {write: jest.fn()};
+    outputStream = {write: jest.fn()};
     globalConfig = {watch: true};
     hasteMapInstances = [{on: () => {}}];
     contexts = [{config}];
@@ -54,45 +54,69 @@ describe('Watch mode flows', () => {
   it('Correctly passing test path pattern', () => {
     globalConfig.testPathPattern = 'test-*';
 
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
 
     expect(runJestMock.mock.calls[0][0]).toMatchObject({
       contexts,
       globalConfig,
       onComplete: expect.any(Function),
-      outputStream: pipe,
+      outputStream,
       testWatcher: new TestWatcher({isWatchMode: true}),
     });
   });
 
   it('Correctly passing test name pattern', () => {
     globalConfig.testNamePattern = 'test-*';
 
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
 
     expect(runJestMock.mock.calls[0][0]).toMatchObject({
       contexts,
       globalConfig,
       onComplete: expect.any(Function),
-      outputStream: pipe,
+      outputStream,
       testWatcher: new TestWatcher({isWatchMode: true}),
     });
   });
 
   it('Runs Jest once by default and shows usage', () => {
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
     expect(runJestMock.mock.calls[0][0]).toMatchObject({
       contexts,
       globalConfig,
       onComplete: expect.any(Function),
-      outputStream: pipe,
+      outputStream,
       testWatcher: new TestWatcher({isWatchMode: true}),
     });
-    expect(pipe.write.mock.calls.reverse()[0]).toMatchSnapshot();
+    expect(outputStream.write.mock.calls.reverse()[0]).toMatchSnapshot();
   });
 
   it('Pressing "o" runs test in "only changed files" mode', () => {
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
     runJestMock.mockReset();
 
     stdin.emit(KEYS.O);
@@ -106,7 +130,13 @@ describe('Watch mode flows', () => {
   });
 
   it('Pressing "a" runs test in "watch all" mode', () => {
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
     runJestMock.mockReset();
 
     stdin.emit(KEYS.A);
@@ -120,14 +150,26 @@ describe('Watch mode flows', () => {
   });
 
   it('Pressing "ENTER" reruns the tests', () => {
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
     expect(runJestMock).toHaveBeenCalledTimes(1);
     stdin.emit(KEYS.ENTER);
     expect(runJestMock).toHaveBeenCalledTimes(2);
   });
 
   it('Pressing "u" reruns the tests in "update snapshot" mode', () => {
-    watch(globalConfig, contexts, pipe, hasteMapInstances, stdin);
+    watch({
+      contexts,
+      globalConfig,
+      hasteMapInstances,
+      outputStream,
+      stdin,
+    });
     runJestMock.mockReset();
 
     stdin.emit(KEYS.U);