write-file-atomic 4.0.2: sync

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 sync in pkg:npm/write-file-atomic@4.0.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/write-file-atomic@4.0.2
Demonstrate these symbols/APIs:
  - sync

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:a3d20939636cc59d46c9ca8e6b3525a1bae13a91a4b415b32f4bcd22135ed1a2","contract":["sync atomically writes string data to target path synchronously","sync atomically writes Buffer binary data to target path synchronously","sync atomically overwrites existing file with new content synchronously without leaving partial state","sync respects custom file mode options when writing synchronously","sync supports custom encoding option when writing string data synchronously","sync throws an error synchronously when target directory does not exist"],"goal":"verify sync in pkg:npm/write-file-atomic@4.0.2","kind":"HOW","packages":["pkg:npm/write-file-atomic@4.0.2"],"schemaVersion":1,"symbols":["sync"]},"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","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/write-file-atomic@4.0.2"],"schemaVersion":1,"subject":"pkg:npm/write-file-atomic@4.0.2","symbols":["sync"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-write-file-atomic",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-write-file-atomic",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "write-file-atomic": "4.0.2"
      }
    },
    "node_modules/imurmurhash": {
      "version": "0.1.4",
      "resolved": "https://registry.npmjs.org/imurmurhash/-/imurmurhash-0.1.4.tgz",
      "integrity": "sha512-JmXMZ6wuvDmLiHEml9ykzqO6lwFbof0GG4IkcGaENdCRDDmMVnny7s5HsIgHCbaq0w2MyPhDqkhTUgS2LU2PHA==",
      "license": "MIT",
      "engines": {
        "node": ">=0.8.19"
      }
    },
    "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"
    },
    "node_modules/write-file-atomic": {
      "version": "4.0.2",
      "resolved": "https://registry.npmjs.org/write-file-atomic/-/write-file-atomic-4.0.2.tgz",
      "integrity": "sha512-7KxauUdBmSdWnmpaGFg+ppNjKF8uNLry8LyzjauQDOVONfFLNKrKvQOxZ/VuTIcS/gge/YNahf5RIIQWTSarlg==",
      "license": "ISC",
      "dependencies": {
        "imurmurhash": "^0.1.4",
        "signal-exit": "^3.0.7"
      },
      "engines": {
        "node": "^12.13.0 || ^14.15.0 || >=16.0.0"
      }
    }
  }
}

{
  "name": "sample-write-file-atomic",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room code sample for write-file-atomic sync",
  "main": "src/index.js",
  "license": "MIT-0",
  "dependencies": {
    "write-file-atomic": "4.0.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify sync in pkg:npm/write-file-atomic@4.0.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/write-file-atomic@4.0.2"
  ],
  "symbols": [
    "sync"
  ]
}

const writeFileAtomic = require('write-file-atomic');

/**
 * Synchronously writes data to a file atomically.
 *
 * @param {string} filename - Target file path.
 * @param {string|Buffer|Uint8Array} data - Data to write.
 * @param {object|string} [options] - Write options (e.g. encoding, mode).
 */
function writeAtomicSync(filename, data, options) {
  return writeFileAtomic.sync(filename, data, options);
}

module.exports = {
  sync: writeFileAtomic.sync,
  writeAtomicSync
};

import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const { sync, writeAtomicSync } = require('../src/index.js');

async function runTests() {
  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'csx-wfa-sync-test-'));

  try {
    // 1. sync atomically writes string data to target path synchronously
    const stringFilePath = path.join(tmpDir, 'test-sync-string.txt');
    const res1 = sync(stringFilePath, 'hello atomic sync world');
    assert.strictEqual(res1, undefined, 'sync should return undefined');
    assert.strictEqual(fs.readFileSync(stringFilePath, 'utf8'), 'hello atomic sync world');

    // 2. sync atomically writes Buffer binary data to target path synchronously
    const binFilePath = path.join(tmpDir, 'test-sync-bin.dat');
    const binData = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
    writeAtomicSync(binFilePath, binData);
    assert.deepEqual(fs.readFileSync(binFilePath), binData);

    // 3. sync atomically overwrites existing file with new content synchronously without leaving partial state
    const overwriteFilePath = path.join(tmpDir, 'test-sync-overwrite.txt');
    fs.writeFileSync(overwriteFilePath, 'initial content before overwrite', 'utf8');
    assert.strictEqual(fs.readFileSync(overwriteFilePath, 'utf8'), 'initial content before overwrite');
    sync(overwriteFilePath, 'overwritten atomic content');
    assert.strictEqual(fs.readFileSync(overwriteFilePath, 'utf8'), 'overwritten atomic content');

    // 4. sync respects custom file mode options when writing synchronously
    const modeFilePath = path.join(tmpDir, 'test-sync-mode.txt');
    sync(modeFilePath, 'custom mode content', { mode: 0o600 });
    assert.strictEqual(fs.readFileSync(modeFilePath, 'utf8'), 'custom mode content');
    const stat = fs.statSync(modeFilePath);
    assert.strictEqual(stat.mode & 0o777, 0o600);

    // 5. sync supports custom encoding option when writing string data synchronously
    const encFilePath = path.join(tmpDir, 'test-sync-enc.txt');
    sync(encFilePath, 'utf8 custom encoding', { encoding: 'utf8' });
    assert.strictEqual(fs.readFileSync(encFilePath, 'utf8'), 'utf8 custom encoding');

    // 6. sync throws an error synchronously when target directory does not exist
    const invalidFilePath = path.join(tmpDir, 'nonexistent-directory', 'file.txt');
    assert.throws(
      () => sync(invalidFilePath, 'should fail'),
      (err) => err && (err.code === 'ENOENT' || err.code === 'ENOTDIR')
    );

    console.log('All contract assertions for write-file-atomic sync passed successfully.');
  } finally {
    fs.rmSync(tmpDir, { recursive: true, force: true });
  }
}

runTests().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
});