proper-lockfile 4.1.2: lockSync

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 proper-lockfile.lockSync in pkg:npm/proper-lockfile@4.1.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/proper-lockfile@4.1.2
Demonstrate these symbols/APIs:
  - proper-lockfile.lockSync

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:afb71c37ffaf7d03ee30dedeb0e6b3cc7b4dadc41798a7036815264ec370f157","contract":["assert lockSync acquires a lock on a file and returns a release function","assert lockSync prevents re-locking an already locked file throwing ELOCKED error","assert release function returned by lockSync releases the lock synchronously","assert lockSync accepts custom options including retries and stale duration","assert unlockSync releases the lock acquired by lockSync synchronously"],"goal":"verify proper-lockfile.lockSync in pkg:npm/proper-lockfile@4.1.2","kind":"HOW","packages":["pkg:npm/proper-lockfile@4.1.2"],"schemaVersion":1,"symbols":["proper-lockfile.lockSync"]},"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/proper-lockfile@4.1.2"],"schemaVersion":1,"subject":"pkg:npm/proper-lockfile@4.1.2","symbols":["proper-lockfile.lockSync"],"verifierAdapter":"node-typescript@1"}

import lockfile, { lockSync, unlockSync, checkSync } from 'proper-lockfile';

/**
 * Synchronously acquires a lock on a file.
 *
 * @param {string} file
 * @param {object} [options]
 * @returns {() => void} release function
 */
export function acquireLockSync(file, options) {
  return lockSync(file, options);
}

/**
 * Synchronously releases a lock on a file.
 *
 * @param {string} file
 * @param {object} [options]
 */
export function releaseLockSync(file, options) {
  return unlockSync(file, options);
}

/**
 * Synchronously checks if a file is currently locked.
 *
 * @param {string} file
 * @param {object} [options]
 * @returns {boolean}
 */
export function isLockedSync(file, options) {
  return checkSync(file, options);
}

export { lockSync, unlockSync, checkSync, lockfile };
export default lockSync;

{
  "name": "sample-proper-lockfile-verify",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-proper-lockfile-verify",
      "version": "1.0.0",
      "dependencies": {
        "proper-lockfile": "4.1.2"
      }
    },
    "node_modules/graceful-fs": {
      "version": "4.2.11",
      "resolved": "https://registry.npmjs.org/graceful-fs/-/graceful-fs-4.2.11.tgz",
      "integrity": "sha512-RbJ5/jmFcNNCcDV5o9eTnBLJ/HszWV0P73bc+Ff4nS/rJj+YaS6IGyiOL0VoBYX+l1Wrl3k63h/KrH+nhJ0XvQ==",
      "license": "ISC"
    },
    "node_modules/proper-lockfile": {
      "version": "4.1.2",
      "resolved": "https://registry.npmjs.org/proper-lockfile/-/proper-lockfile-4.1.2.tgz",
      "integrity": "sha512-TjNPblN4BwAWMXU8s9AEz4JmQxnD1NNL7bNOY/AKUzyamc379FWASUhc/K1pL2noVb+XmZKLL68cjzLsiOAMaA==",
      "license": "MIT",
      "dependencies": {
        "graceful-fs": "^4.2.4",
        "retry": "^0.12.0",
        "signal-exit": "^3.0.2"
      }
    },
    "node_modules/retry": {
      "version": "0.12.0",
      "resolved": "https://registry.npmjs.org/retry/-/retry-0.12.0.tgz",
      "integrity": "sha512-9LkiTwjUh6rT555DtE9rTX+BKByPfrMzEAtnlEtdEwr3Nkffwiihqe2bWADg+OQRjt9gl6ICdmB/ZFDCGAtSow==",
      "license": "MIT",
      "engines": {
        "node": ">= 4"
      }
    },
    "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-proper-lockfile-verify",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "dependencies": {
    "proper-lockfile": "4.1.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify proper-lockfile.lockSync in pkg:npm/proper-lockfile@4.1.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/proper-lockfile@4.1.2"
  ],
  "symbols": [
    "proper-lockfile.lockSync"
  ]
}

import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import {
  lockSync,
  unlockSync,
  checkSync,
  acquireLockSync,
  releaseLockSync,
  isLockedSync,
} from '../index.mjs';

function createTempTestFile() {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'csx-lock-test-'));
  const filePath = path.join(tempDir, 'target.txt');
  fs.writeFileSync(filePath, 'contract test payload');
  return {
    filePath,
    cleanup: () => {
      try {
        fs.rmSync(tempDir, { recursive: true, force: true });
      } catch {}
    },
  };
}

// 1. assert lockSync acquires a lock on a file and returns a release function
{
  const { filePath, cleanup } = createTempTestFile();
  try {
    assert.strictEqual(isLockedSync(filePath), false);
    const release = acquireLockSync(filePath);
    assert.strictEqual(typeof release, 'function');
    assert.strictEqual(isLockedSync(filePath), true);
    release();
    assert.strictEqual(isLockedSync(filePath), false);
  } finally {
    cleanup();
  }
}

// 2. assert lockSync prevents re-locking an already locked file throwing ELOCKED error
{
  const { filePath, cleanup } = createTempTestFile();
  try {
    const release = lockSync(filePath);
    assert.throws(
      () => {
        lockSync(filePath);
      },
      (err) => {
        assert.strictEqual(err.code, 'ELOCKED');
        return true;
      }
    );
    release();
  } finally {
    cleanup();
  }
}

// 3. assert release function returned by lockSync releases the lock synchronously
{
  const { filePath, cleanup } = createTempTestFile();
  try {
    const release = lockSync(filePath);
    assert.strictEqual(checkSync(filePath), true);
    release();
    assert.strictEqual(checkSync(filePath), false);
  } finally {
    cleanup();
  }
}

// 4. assert lockSync accepts custom options including retries and stale duration
{
  const { filePath, cleanup } = createTempTestFile();
  try {
    const release = lockSync(filePath, { stale: 6000, retries: 0 });
    assert.strictEqual(checkSync(filePath, { stale: 6000 }), true);
    release();
    assert.strictEqual(checkSync(filePath), false);
  } finally {
    cleanup();
  }
}

// 5. assert unlockSync releases the lock acquired by lockSync synchronously
{
  const { filePath, cleanup } = createTempTestFile();
  try {
    lockSync(filePath);
    assert.strictEqual(checkSync(filePath), true);
    releaseLockSync(filePath);
    assert.strictEqual(checkSync(filePath), false);
  } finally {
    cleanup();
  }
}

console.log('All proper-lockfile.lockSync contract assertions passed.');