signal-exit 3.0.7

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:npm/signal-exit@3.0.7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/signal-exit@3.0.7
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:1c92273ec54f68150fc27d112b87417f352dffff5dcf9b01b339be09f4668bec","constraints":{"executionContext":"node"},"contract":["onExit registers an exit callback and returns an unregister function","calling the returned unregister function prevents the exit callback from firing","onExit throws AssertionError when a non-function callback is passed","onExit callback receives the numeric exit code when process.exit is called","onExit callback receives exit code 0 when the Node.js event loop terminates naturally","onExit callback receives the signal name when the process receives a termination signal","onExit with alwaysLast option executes after standard exit listeners","signals export provides an array of standard POSIX termination signal names","load and unload functions control the lifecycle of process exit listeners"],"goal":"verify pkg:npm/signal-exit@3.0.7","kind":"HOW","packages":["pkg:npm/signal-exit@3.0.7"],"schemaVersion":1},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/signal-exit@3.0.7"],"schemaVersion":1,"subject":"pkg:npm/signal-exit@3.0.7","verifierAdapter":"node-typescript@1"}

{
  "name": "sample-signal-exit",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-signal-exit",
      "version": "1.0.0",
      "dependencies": {
        "signal-exit": "3.0.7"
      }
    },
    "node_modules/signal-exit": {
      "version": "3.0.7",
      "resolved": "https://registry.npmjs.org/signal-exit/-/signal-exit-3.0.7.tgz",
      "integrity": "sha512-wnD2ZE+l+SPC/uoS0vXeE9L1+0wuaMqKlfz9AMUo38JsyLSBWSFcHR1Rri62LZc12vLr1gb3jl7iwQhgwpAbGQ==",
      "license": "ISC"
    }
  }
}

{
  "name": "sample-signal-exit",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "signal-exit": "3.0.7"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/signal-exit@3.0.7",
  "kind": "HOW",
  "packages": [
    "pkg:npm/signal-exit@3.0.7"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert/strict';
import { spawn, spawnSync } from 'node:child_process';
import onExit from 'signal-exit';

// 1. onExit registers an exit callback and returns an unregister function
{
	const unregister = onExit(() => {});
	assert.equal(typeof unregister, 'function');
	unregister();
}

// 2. calling the returned unregister function prevents the exit callback from firing
{
	const code = `
		const onExit = require('signal-exit');
		const remove = onExit(() => {
			process.stdout.write('UNREGISTER_FAILED');
		});
		remove();
		process.exit(0);
	`;
	const res = spawnSync(process.execPath, ['-e', code], { encoding: 'utf8' });
	assert.equal(res.status, 0);
	assert.ok(!res.stdout.includes('UNREGISTER_FAILED'));
}

// 3. onExit throws AssertionError when a non-function callback is passed
{
	assert.throws(
		() => {
			onExit(null);
		},
		{
			name: 'AssertionError',
		}
	);
}

// 4. onExit callback receives the numeric exit code when process.exit is called
{
	const code = `
		const fs = require('fs');
		const onExit = require('signal-exit');
		onExit((code, signal) => {
			fs.writeSync(1, 'EXIT_CODE:' + code + ':' + signal);
		});
		process.exit(42);
	`;
	const res = spawnSync(process.execPath, ['-e', code], { encoding: 'utf8' });
	assert.equal(res.status, 42);
	assert.ok(res.stdout.includes('EXIT_CODE:42:null'));
}

// 5. onExit callback receives exit code 0 when the Node.js event loop terminates naturally
{
	const code = `
		const fs = require('fs');
		const onExit = require('signal-exit');
		onExit((code, signal) => {
			fs.writeSync(1, 'NATURAL_EXIT:' + code + ':' + signal);
		});
	`;
	const res = spawnSync(process.execPath, ['-e', code], { encoding: 'utf8' });
	assert.equal(res.status, 0);
	assert.ok(res.stdout.includes('NATURAL_EXIT:0:null'));
}

// 6. onExit callback receives the signal name when the process receives a termination signal
await new Promise((resolve, reject) => {
	const code = `
		const fs = require('fs');
		const onExit = require('signal-exit');
		onExit((code, signal) => {
			fs.writeSync(1, 'SIGNAL:' + signal);
		});
		setInterval(() => {}, 1000);
	`;
	const child = spawn(process.execPath, ['-e', code], { stdio: ['pipe', 'pipe', 'inherit'] });
	let out = '';
	child.stdout.on('data', (d) => {
		out += d.toString();
	});
	setTimeout(() => {
		child.kill('SIGTERM');
	}, 100);
	child.on('close', () => {
		try {
			assert.ok(out.includes('SIGNAL:SIGTERM'));
			resolve();
		} catch (err) {
			reject(err);
		}
	});
});

// 7. onExit with alwaysLast option executes after standard exit listeners
{
	const code = `
		const fs = require('fs');
		const onExit = require('signal-exit');
		onExit((code, signal) => {
			fs.writeSync(1, 'LAST\\n');
		}, { alwaysLast: true });
		onExit((code, signal) => {
			fs.writeSync(1, 'FIRST\\n');
		});
		process.exit(0);
	`;
	const res = spawnSync(process.execPath, ['-e', code], { encoding: 'utf8' });
	assert.equal(res.status, 0);
	assert.equal(res.stdout, 'FIRST\nLAST\n');
}

// 8. signals export provides an array of standard POSIX termination signal names
{
	const sigs = onExit.signals();
	assert.ok(Array.isArray(sigs));
	assert.ok(sigs.includes('SIGINT'));
	assert.ok(sigs.includes('SIGTERM'));
	assert.ok(sigs.includes('SIGHUP'));
}

// 9. load and unload functions control the lifecycle of process exit listeners
{
	assert.equal(typeof onExit.load, 'function');
	assert.equal(typeof onExit.unload, 'function');
	onExit.load();
	onExit.unload();
}