feat: add option to use posix exit code upon fatal signal (#4989)

Co-authored-by: Josh Goldberg ✨ <git@joshuakgoldberg.com>
Co-authored-by: Pelle Wessman <pelle@kodfabrik.se>

Author: 3 people

bin/mocha.js

@@ -10,6 +10,7 @@
  * @private
  */
 
+const os = require('node:os');
 const {loadOptions} = require('../lib/cli/options');
 const {
   unparseNodeFlags,
@@ -22,6 +23,7 @@ const {aliases} = require('../lib/cli/run-option-metadata');
 
 const mochaArgs = {};
 const nodeArgs = {};
+const SIGNAL_OFFSET = 128;
 let hasInspect = false;
 
 const opts = loadOptions(process.argv.slice(2));
@@ -109,9 +111,13 @@ if (mochaArgs['node-option'] || Object.keys(nodeArgs).length || hasInspect) {
   proc.on('exit', (code, signal) => {
     process.on('exit', () => {
       if (signal) {
+        signal = typeof signal === 'string' ? os.constants.signals[signal] : signal;
+        if (mochaArgs['posix-exit-codes'] === true) {
+          process.exitCode = SIGNAL_OFFSET + signal;
+        }
         process.kill(process.pid, signal);
       } else {
-        process.exit(code);
+        process.exit(Math.min(code, mochaArgs['posix-exit-codes'] ? 1 : 255));
       }
     });
   });
@@ -126,7 +132,7 @@ if (mochaArgs['node-option'] || Object.keys(nodeArgs).length || hasInspect) {
     // be needed.
     if (!args.parallel || args.jobs < 2) {
       // win32 does not support SIGTERM, so use next best thing.
-      if (require('node:os').platform() === 'win32') {
+      if (os.platform() === 'win32') {
         proc.kill('SIGKILL');
       } else {
         // using SIGKILL won't cleanly close the output streams, which can result

docs/index.md

@@ -963,6 +963,18 @@ Define a global variable name. For example, suppose your app deliberately expose
 
 By using this option in conjunction with `--check-leaks`, you can specify a whitelist of known global variables that you _expect_ to leak into global scope.
 
+### `--posix-exit-codes`
+
+Exits with standard POSIX exit codes instead of the number of failed tests.
+
+Those exit codes are:
+
+- `0`: if all tests passed
+- `1`: if any test failed
+- `128 + <signal>` if given a signal, such as:
+  - 134: `SIGABRT` (`128 + 6`)
+  - 143: `SIGTERM` (`128 + 15`)
+
 ### `--retries <n>`
 
 Retries failed tests `n` times.

lib/cli/run-helpers.js

@@ -27,7 +27,7 @@ const {UnmatchedFile} = require('./collect-files');
  */
 const exitMochaLater = clampedCode => {
   process.on('exit', () => {
-    process.exitCode = clampedCode;
+    process.exitCode = Math.min(clampedCode, process.argv.includes('--posix-exit-codes') ? 1 : 255);
   });
 };
 
@@ -39,6 +39,8 @@ const exitMochaLater = clampedCode => {
  * @private
  */
 const exitMocha = clampedCode => {
+  const usePosixExitCodes = process.argv.includes('--posix-exit-codes');
+  clampedCode = Math.min(clampedCode, usePosixExitCodes ? 1 : 255);
   let draining = 0;
 
   // Eagerly set the process's exit code in case stream.write doesn't

lib/cli/run-option-metadata.js

@@ -46,6 +46,7 @@ const TYPES = (exports.types = {
     'list-reporters',
     'no-colors',
     'parallel',
+    'posix-exit-codes',
     'recursive',
     'sort',
     'watch'

lib/cli/run.js

@@ -195,6 +195,10 @@ exports.builder = yargs =>
         description: 'Run tests in parallel',
         group: GROUPS.RULES
       },
+      'posix-exit-codes': {
+        description: 'Use POSIX and UNIX shell exit codes as Mocha\'s return value',
+        group: GROUPS.RULES
+      },
       recursive: {
         description: 'Look for tests in subdirectories',
         group: GROUPS.FILES

test/integration/fixtures/failing.fixture.js

@@ -0,0 +1,23 @@
+'use strict';
+
+// One passing test and three failing tests
+
+var assert = require('assert');
+
+describe('suite', function () {
+  it('test1', function () {
+    assert(true);
+  });
+
+  it('test2', function () {
+    assert(false);
+  });
+
+  it('test3', function () {
+    assert(false);
+  });
+
+  it('test4', function () {
+    assert(false);
+  });
+});

test/integration/fixtures/signals-sigabrt.fixture.js

@@ -0,0 +1,7 @@
+'use strict';
+
+describe('signal suite', function () {
+  it('test SIGABRT', function () {
+    process.kill(process.pid, 'SIGABRT');
+  });
+});

test/integration/fixtures/signals-sigterm-numeric.fixture.js

@@ -0,0 +1,8 @@
+'use strict';
+const os = require('node:os');
+
+describe('signal suite', function () {
+  it('test SIGTERM', function () {
+    process.kill(process.pid, os.constants.signals['SIGTERM']);
+  });
+});

test/integration/fixtures/signals-sigterm.fixture.js

@@ -0,0 +1,7 @@
+'use strict';
+
+describe('signal suite', function () {
+  it('test SIGTERM', function () {
+    process.kill(process.pid, 'SIGTERM');
+  });
+});

test/integration/helpers.js

@@ -8,6 +8,7 @@ const {format} = require('node:util');
 const path = require('node:path');
 const Base = require('../../lib/reporters/base');
 const debug = require('debug')('mocha:test:integration:helpers');
+const SIGNAL_OFFSET = 128;
 
 /**
  * Path to `mocha` executable
@@ -358,6 +359,18 @@ function createSubprocess(args, done, opts = {}) {
     });
   });
 
+  /**
+   * Emulate node's exit code for fatal signal. Allows tests to see the same
+   * exit code as the mocha cli.
+   */
+  mocha.on('exit', (code, signal) => {
+    if (signal) {
+      mocha.exitCode =
+        SIGNAL_OFFSET +
+        (typeof signal == 'string' ? os.constants.signals[signal] : signal);
+    }
+  });
+
   return mocha;
 }