graceful-fs 4.2.11: writeFile

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 graceful-fs.writeFile in pkg:npm/graceful-fs@4.2.11
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/graceful-fs@4.2.11
Demonstrate these symbols/APIs:
  - graceful-fs.writeFile

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:b55183a2dc7b045a8ad6dcfee3e83c92b3b11a0f7d0fdf940b3f81705c4c8173","contract":["assert writeFile is exported as a function by graceful-fs","assert writeFile asynchronously writes utf-8 text with callback","assert writeFile writes binary buffer data to destination file","assert writeFile supports options flag to append data to existing file","assert writeFile yields ENOENT error in callback when target directory does not exist","assert graceful-fs promises exposes writeFile returning a Promise"],"goal":"verify graceful-fs.writeFile in pkg:npm/graceful-fs@4.2.11","kind":"HOW","packages":["pkg:npm/graceful-fs@4.2.11"],"schemaVersion":1,"symbols":["graceful-fs.writeFile"]},"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/graceful-fs@4.2.11"],"schemaVersion":1,"subject":"pkg:npm/graceful-fs@4.2.11","symbols":["graceful-fs.writeFile"],"verifierAdapter":"node-typescript@1"}

const gracefulFs = require('graceful-fs');

/**
 * Writes data to a file using graceful-fs writeFile.
 *
 * @param {string} filePath - Path to destination file.
 * @param {string|Buffer} data - Data to write.
 * @param {object|string} [options] - Write options.
 * @param {Function} callback - Callback invoked on completion.
 */
function writeToFile(filePath, data, options, callback) {
  if (typeof options === 'function') {
    callback = options;
    options = {};
  }
  return gracefulFs.writeFile(filePath, data, options, callback);
}

module.exports = {
  gracefulFs,
  writeFile: gracefulFs.writeFile,
  writeToFile,
};

{
  "name": "sample-graceful-fs-writefile",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-graceful-fs-writefile",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "graceful-fs": "4.2.11"
      }
    },
    "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"
    }
  }
}

{
  "name": "sample-graceful-fs-writefile",
  "version": "1.0.0",
  "description": "Clean-room sample verifying graceful-fs.writeFile in pkg:npm/graceful-fs@4.2.11",
  "main": "index.js",
  "type": "commonjs",
  "license": "MIT-0",
  "dependencies": {
    "graceful-fs": "4.2.11"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify graceful-fs.writeFile in pkg:npm/graceful-fs@4.2.11",
  "kind": "HOW",
  "packages": [
    "pkg:npm/graceful-fs@4.2.11"
  ],
  "symbols": [
    "graceful-fs.writeFile"
  ]
}

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

const require = createRequire(import.meta.url);
const {
  gracefulFs,
  writeFile,
  writeToFile,
} = require('../index.js');

const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'graceful-fs-write-contract-'));

try {
  // Contract 1: assert writeFile is exported as a function by graceful-fs
  assert.strictEqual(typeof writeFile, 'function', 'writeFile must be a function');
  assert.strictEqual(typeof gracefulFs.writeFile, 'function', 'gracefulFs.writeFile must be a function');

  // Contract 2: assert writeFile asynchronously writes utf-8 text with callback
  const textFile = path.join(tmpDir, 'test-write.txt');
  const payload = 'graceful-fs-write-content-verification';
  await new Promise((resolve, reject) => {
    writeToFile(textFile, payload, 'utf8', (err) => {
      if (err) return reject(err);
      gracefulFs.readFile(textFile, 'utf8', (readErr, content) => {
        if (readErr) return reject(readErr);
        assert.strictEqual(content, payload, 'file content must match written payload');
        resolve();
      });
    });
  });

  // Contract 3: assert writeFile writes binary buffer data to destination file
  const binFile = path.join(tmpDir, 'test-bin.dat');
  const binData = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x9a, 0xbc]);
  await new Promise((resolve, reject) => {
    writeToFile(binFile, binData, (err) => {
      if (err) return reject(err);
      gracefulFs.readFile(binFile, (readErr, content) => {
        if (readErr) return reject(readErr);
        assert.deepStrictEqual(content, binData, 'binary file content must match written buffer');
        resolve();
      });
    });
  });

  // Contract 4: assert writeFile supports options flag to append data to existing file
  const appendChunk = '\nappended-content';
  await new Promise((resolve, reject) => {
    writeToFile(textFile, appendChunk, { flag: 'a', encoding: 'utf8' }, (err) => {
      if (err) return reject(err);
      gracefulFs.readFile(textFile, 'utf8', (readErr, content) => {
        if (readErr) return reject(readErr);
        assert.strictEqual(content, payload + appendChunk, 'appended content must be present at end of file');
        resolve();
      });
    });
  });

  // Contract 5: assert writeFile yields ENOENT error in callback when target directory does not exist
  const nonexistentDirFile = path.join(tmpDir, 'nonexistent-directory', 'file.txt');
  await new Promise((resolve, reject) => {
    writeToFile(nonexistentDirFile, 'data', (err) => {
      assert.ok(err, 'writing to nonexistent directory must produce an error');
      assert.strictEqual(err.code, 'ENOENT', 'error code must be ENOENT');
      resolve();
    });
  });

  // Contract 6: assert graceful-fs promises exposes writeFile returning a Promise
  assert.strictEqual(typeof gracefulFs.promises?.writeFile, 'function', 'promises.writeFile must be a function');
  const promiseFile = path.join(tmpDir, 'test-promise.txt');
  const promisePayload = 'promise-written-text';
  await gracefulFs.promises.writeFile(promiseFile, promisePayload, 'utf8');
  const promiseRead = await gracefulFs.promises.readFile(promiseFile, 'utf8');
  assert.strictEqual(promiseRead, promisePayload, 'content written by promises.writeFile must match');

  console.log('All contract assertions passed.');
} finally {
  fs.rmSync(tmpDir, { recursive: true, force: true });
}