Add --detectOpenHandles flag (#6130)

* why-running

* add --detectOpenHandles flag

* move processing of w-i-n-r into separate function

* pretty-print open handles

* docs

* update snapshots

* ensure empty when flag not used

* please flow gods

* add pretty colors

* less if

* use pluralize

* Revert "less if"

This reverts commit dd71548.

* extract formatting of why-running

* cmon flow, be nice

* use code frame

* Implement async_hooks manually

* nudge users towards new feature

* make handlers better match other error output

* add tests

* PR feeback

* really fic PR feedback

Author: SimenB

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();
+});