Add --detectOpenHandles flag

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ### Features
 
+* `[jest-cli]` Add `--detectOpenHandles` flag which enables Jest to potentially
+  track down handles keeping it open after tests are complete.
+  ([#6130](https://github.com/facebook/jest/pull/6130))
 * `[jest-jasmine2]` Add data driven testing based on `jest-each`
   ([#6102](https://github.com/facebook/jest/pull/6102))
 * `[jest-matcher-utils]` Change "suggest to equal" message to be more advisory

TestUtils.js

@@ -22,6 +22,7 @@ const DEFAULT_GLOBAL_CONFIG: GlobalConfig = {
   coverageReporters: [],
   coverageThreshold: {global: {}},
   detectLeaks: false,
+  detectOpenHandles: false,
   enabledTestsMap: null,
   expand: false,
   filter: null,
@@ -72,6 +73,7 @@ const DEFAULT_PROJECT_CONFIG: ProjectConfig = {
   coveragePathIgnorePatterns: [],
   cwd: '/test_root_dir/',
   detectLeaks: false,
+  detectOpenHandles: false,
   displayName: undefined,
   filter: null,
   forceCoverageMatch: [],

docs/CLI.md

@@ -172,6 +172,14 @@ output.
 
 Print debugging info about your Jest config.
 
+### `--detectOpenHandles`
+
+Attempt to collect and print open handles preventing Jest from exiting cleanly.
+Use this in cases where you need to use `--forceExit` in order for Jest to exit
+to potentially track down the reason. Implemented using
+[`async_hooks`](https://nodejs.org/api/async_hooks.html), so it only works in
+Node 8 and newer.
+
 ### `--env=<environment>`
 
 The test environment used for all tests. This can point to any file or node
@@ -196,7 +204,8 @@ resources set up by test code cannot be adequately cleaned up. _Note: This
 feature is an escape-hatch. If Jest doesn't exit at the end of a test run, it
 means external resources are still being held on to or timers are still pending
 in your code. It is advised to tear down external resources after each test to
-make sure Jest can shut down cleanly._
+make sure Jest can shut down cleanly. You can use `--detectOpenHandles` to help
+track it down._
 
 ### `--help`
 

docs/Configuration.md

@@ -963,6 +963,7 @@ structure as the first argument and return it:
   "numPassedTests": number,
   "numFailedTests": number,
   "numPendingTests": number,
+  "openHandles": Array<Error>,
   "testResults": [{
     "numFailingTests": number,
     "numPassingTests": number,

integration-tests/Utils.js

@@ -156,7 +156,7 @@ const extractSummary = (
 
   let rest = cleanupStackTrace(
     // remove all timestamps
-    stdout.slice(0, -match[0].length).replace(/\s*\(\d*\.?\d+m?s\)$/gm, ''),
+    stdout.replace(match[0], '').replace(/\s*\(\d*\.?\d+m?s\)$/gm, ''),
   );
 
   if (stripLocation) {

integration-tests/__tests__/__snapshots__/cli-handles-exact-filenames.test.js.snap

@@ -4,7 +4,10 @@ exports[`CLI accepts exact file names if matchers matched 1`] = `
 "PASS foo/bar.spec.js
   ✓ foo
 
-"
+
+Force exiting Jest
+
+Have you considered using \`--detectOpenHandles\` to detect async operations that kept running after all tests finished?"
 `;
 
 exports[`CLI accepts exact file names if matchers matched 2`] = `

integration-tests/__tests__/__snapshots__/console_log_output_when_run_in_band.test.js.snap

@@ -4,7 +4,10 @@ exports[`prints console.logs when run with forceExit 1`] = `
 "PASS __tests__/a-banana.js
   ✓ banana
 
-"
+
+Force exiting Jest
+
+Have you considered using \`--detectOpenHandles\` to detect async operations that kept running after all tests finished?"
 `;
 
 exports[`prints console.logs when run with forceExit 2`] = `

integration-tests/__tests__/__snapshots__/detect_open_handles.js.snap

@@ -0,0 +1,28 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`prints message about flag on forceExit 1`] = `
+"Force exiting Jest
+
+Have you considered using \`--detectOpenHandles\` to detect async operations that kept running after all tests finished?"
+`;
+
+exports[`prints message about flag on slow tests 1`] = `
+"Jest did not exit one second after the test run has completed.
+
+This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with \`--detectOpenHandles\` to troubleshoot this issue."
+`;
+
+exports[`prints out info about open handlers 1`] = `
+"Jest has detected the following 1 open handle potentially keeping Jest from exiting:
+
+  ●  GETADDRINFOREQWRAP
+
+      5 | const app = new http.Server();
+      6 | 
+    > 7 | app.listen({host: 'localhost', port: 0});
+        |     ^
+      8 | 
+
+      at Object.<anonymous> (server.js:7:5)
+      at Object.<anonymous> (__tests__/test.js:3:1)"
+`;

integration-tests/__tests__/__snapshots__/show_config.test.js.snap

@@ -13,6 +13,7 @@ exports[`--showConfig outputs config info and exits 1`] = `
         \\"/node_modules/\\"
       ],
       \\"detectLeaks\\": false,
+      \\"detectOpenHandles\\": false,
       \\"filter\\": null,
       \\"forceCoverageMatch\\": [],
       \\"globals\\": {},
@@ -79,6 +80,7 @@ exports[`--showConfig outputs config info and exits 1`] = `
       \\"clover\\"
     ],
     \\"detectLeaks\\": false,
+    \\"detectOpenHandles\\": false,
     \\"expand\\": false,
     \\"filter\\": null,
     \\"globalSetup\\": null,

integration-tests/__tests__/detect_open_handles.js

@@ -0,0 +1,62 @@
+/**
+ * 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');
+
+try {
+  // $FlowFixMe: Node core
+  require('async_hooks');
+} catch (e) {
+  if (e.code === 'MODULE_NOT_FOUND') {
+    // eslint-disable-next-line jest/no-focused-tests
+    fit('skip test for unsupported nodes', () => {
+      console.warn('Skipping test for node ' + process.version);
+    });
+  } else {
+    throw e;
+  }
+}
+
+function getTextAfterTest(stderr) {
+  return stderr.split('Ran all test suites.')[1].trim();
+}
+
+it('prints message about flag on slow tests', async () => {
+  const {stderr} = await runJest.until(
+    'detect-open-handles',
+    [],
+    'Jest did not exit one second after the test run has completed.',
+  );
+  const textAfterTest = getTextAfterTest(stderr);
+
+  expect(textAfterTest).toMatchSnapshot();
+});
+
+it('prints message about flag on forceExit', async () => {
+  const {stderr} = await runJest.until(
+    'detect-open-handles',
+    ['--forceExit'],
+    'Force exiting Jest',
+  );
+  const textAfterTest = getTextAfterTest(stderr);
+
+  expect(textAfterTest).toMatchSnapshot();
+});
+
+it('prints out info about open handlers', async () => {
+  const {stderr} = await runJest.until(
+    'detect-open-handles',
+    ['--detectOpenHandles'],
+    'Jest has detected',
+  );
+  const textAfterTest = getTextAfterTest(stderr);
+
+  expect(textAfterTest).toMatchSnapshot();
+});

integration-tests/detect-open-handles/__tests__/test.js

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

integration-tests/detect-open-handles/package.json

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

integration-tests/detect-open-handles/server.js

@@ -0,0 +1,7 @@
+'use strict';
+
+const http = require('http');
+
+const app = new http.Server();
+
+app.listen({host: 'localhost', port: 0});

integration-tests/runJest.js

@@ -9,9 +9,12 @@
 'use strict';
 
 const path = require('path');
-const {sync: spawnSync} = require('execa');
+const execa = require('execa');
+const {Writable} = require('readable-stream');
 const {fileExists} = require('./Utils');
 
+const {sync: spawnSync} = execa;
+
 const JEST_PATH = path.resolve(__dirname, '../packages/jest-cli/bin/jest.js');
 
 type RunJestOptions = {
@@ -67,9 +70,9 @@ function runJest(
 //   'success', 'startTime', 'numTotalTests', 'numTotalTestSuites',
 //   'numRuntimeErrorTestSuites', 'numPassedTests', 'numFailedTests',
 //   'numPendingTests', 'testResults'
-runJest.json = function(dir: string, args?: Array<string>) {
+runJest.json = function(dir: string, args?: Array<string>, ...rest) {
   args = [...(args || []), '--json'];
-  const result = runJest(dir, args);
+  const result = runJest(dir, args, ...rest);
   try {
     result.json = JSON.parse((result.stdout || '').toString());
   } catch (e) {
@@ -85,4 +88,64 @@ runJest.json = function(dir: string, args?: Array<string>) {
   return result;
 };
 
+// Runs `jest` until a given output is achieved, then kills it with `SIGTERM`
+runJest.until = async function(
+  dir: string,
+  args?: Array<string>,
+  text: string,
+  options: RunJestOptions = {},
+) {
+  const isRelative = dir[0] !== '/';
+
+  if (isRelative) {
+    dir = path.resolve(__dirname, dir);
+  }
+
+  const localPackageJson = path.resolve(dir, 'package.json');
+  if (!options.skipPkgJsonCheck && !fileExists(localPackageJson)) {
+    throw new Error(
+      `
+      Make sure you have a local package.json file at
+        "${localPackageJson}".
+      Otherwise Jest will try to traverse the directory tree and find the
+      the global package.json, which will send Jest into infinite loop.
+    `,
+    );
+  }
+
+  const env = options.nodePath
+    ? Object.assign({}, process.env, {
+        FORCE_COLOR: 0,
+        NODE_PATH: options.nodePath,
+      })
+    : process.env;
+
+  const jestPromise = execa(JEST_PATH, args || [], {
+    cwd: dir,
+    env,
+    reject: false,
+  });
+
+  jestPromise.stderr.pipe(
+    new Writable({
+      write(chunk, encoding, callback) {
+        const output = chunk.toString('utf8');
+
+        if (output.includes(text)) {
+          jestPromise.kill();
+        }
+
+        callback();
+      },
+    }),
+  );
+
+  const result = await jestPromise;
+
+  // For compat with cross-spawn
+  result.status = result.code;
+
+  return result;
+};
+
 module.exports = runJest;

package.json

@@ -57,6 +57,7 @@
     "prettier": "^1.12.1",
     "prettylint": "^1.0.0",
     "progress": "^2.0.0",
+    "readable-stream": "^2.3.6",
     "regenerator-runtime": "^0.11.0",
     "resolve": "^1.4.0",
     "rimraf": "^2.6.2",

packages/jest-circus/src/legacy_code_todo_rewrite/jest_adapter_init.js

@@ -132,6 +132,7 @@ export const runAndTransformResultsToJestFormat = async ({
     numFailingTests,
     numPassingTests,
     numPendingTests,
+    openHandles: [],
     perfStats: {
       // populated outside
       end: 0,

packages/jest-cli/src/cli/args.js

@@ -225,6 +225,13 @@ export const options = {
       'if it was leaked',
     type: 'boolean',
   },
+  detectOpenHandles: {
+    default: false,
+    description:
+      'Print out remaining open handles preventing Jest from exiting at the ' +
+      'end of a test run.',
+    type: 'boolean',
+  },
   env: {
     description:
       'The test environment used for all tests. This can point to ' +