signal-exit 4.1.0

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@4.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/signal-exit@4.1.0

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:sha256:4a938f4764183a7c899a81e9186d80e611c1731583eabdde9cd75a2843486ea3","contract":["onExit registers an exit callback and returns an unregister function","calling the returned unregister function prevents the callback from firing","onExit callback receives the numeric exit code when process.exit is called","onExit callback receives code 0 when the event loop drains naturally","signals export provides an array of standard POSIX signal names"],"goal":"verify pkg:npm/signal-exit@4.1.0","kind":"HOW","packages":["pkg:npm/signal-exit@4.1.0"],"schemaVersion":1},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/signal-exit@4.1.0"],"schemaVersion":1,"subject":"pkg:npm/signal-exit@4.1.0","verifierAdapter":"node-typescript@1"}

{
  "name": "verify-signal-exit",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "verify-signal-exit",
      "version": "1.0.0",
      "dependencies": {
        "signal-exit": "4.1.0"
      }
    },
    "node_modules/signal-exit": {
      "version": "4.1.0",
      "resolved": "https://registry.npmjs.org/signal-exit/-/signal-exit-4.1.0.tgz",
      "integrity": "sha512-bzyZ1e88w9O1iNJbKnOlvYTrWPDl46O1bG0D3XInv+9tkPrxrN8jUUTiFlDkkmKWgn1M6CfIA13SuGqOa9Korw==",
      "license": "ISC",
      "engines": {
        "node": ">=14"
      },
      "funding": {
        "url": "https://github.com/sponsors/isaacs"
      }
    }
  }
}

{
  "name": "verify-signal-exit",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "signal-exit": "4.1.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/signal-exit@4.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/signal-exit@4.1.0"
  ]
}

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

// 1. Verify exports and types
assert.equal(typeof onExit, 'function', 'onExit must be a function');
assert.ok(Array.isArray(signals), 'signals must be an array');
assert.ok(signals.includes('SIGINT'), 'signals array should contain SIGINT');
assert.ok(signals.includes('SIGTERM'), 'signals array should contain SIGTERM');

// 2. Verify onExit returns an unregister function
const remove = onExit(() => {});
assert.equal(typeof remove, 'function', 'onExit must return an unregister function');
remove();

// 3. Test exit handler invocation on process.exit
const exitTestCode = `
import { onExit } from 'signal-exit';
onExit((code, signal) => {
  process.stdout.write('EXIT_CODE:' + code + ',SIGNAL:' + signal + '\\n');
});
process.exit(42);
`;

const exitRes = spawnSync(process.execPath, ['--input-type=module', '-e', exitTestCode], {
  encoding: 'utf8',
});
assert.equal(exitRes.status, 42, 'Child process should exit with code 42');
assert.ok(exitRes.stdout.includes('EXIT_CODE:42,SIGNAL:null'), 'Exit handler must receive exit code 42');

// 4. Test unregister function prevents handler invocation
const unregTestCode = `
import { onExit } from 'signal-exit';
const unreg = onExit(() => {
  process.stdout.write('UNEXPECTED_CALL\\n');
});
unreg();
process.exit(0);
`;

const unregRes = spawnSync(process.execPath, ['--input-type=module', '-e', unregTestCode], {
  encoding: 'utf8',
});
assert.equal(unregRes.status, 0, 'Child process should exit with code 0');
assert.ok(!unregRes.stdout.includes('UNEXPECTED_CALL'), 'Unregistered handler must not be invoked');

// 5. Test exit handler invocation on event loop drain
const drainTestCode = `
import { onExit } from 'signal-exit';
onExit((code, signal) => {
  process.stdout.write('DRAIN_CODE:' + code + ',SIGNAL:' + signal + '\\n');
});
`;

const drainRes = spawnSync(process.execPath, ['--input-type=module', '-e', drainTestCode], {
  encoding: 'utf8',
});
assert.equal(drainRes.status, 0, 'Child process should exit with code 0 on event loop drain');
assert.ok(drainRes.stdout.includes('DRAIN_CODE:0,SIGNAL:null'), 'Exit handler must receive code 0 on natural exit');

console.log('Contract verification passed for signal-exit');