readable-stream 2.3.8: Writable

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 readable-stream.Writable in pkg:npm/readable-stream@2.3.8
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/readable-stream@2.3.8
Demonstrate these symbols/APIs:
  - readable-stream.Writable

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:sha256:3af9d4a578466a185da48fe51c28e3bf3f6449fd75c5dad0bd173dbeb251f3d0","contract":["Writable stream buffers and processes written chunks and emits finish event on end","Writable stream write method invokes callback upon successful chunk processing","Writable stream with objectMode accepts and collects arbitrary JavaScript objects"],"goal":"verify readable-stream.Writable in pkg:npm/readable-stream@2.3.8","kind":"HOW","packages":["pkg:npm/readable-stream@2.3.8"],"schemaVersion":1,"symbols":["readable-stream.Writable"]},"contractCommand":["node","test/contract.js"],"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/readable-stream@2.3.8"],"schemaVersion":1,"subject":"pkg:npm/readable-stream@2.3.8","symbols":["readable-stream.Writable"],"verifierAdapter":"node-typescript@1"}

const { Writable } = require('readable-stream');

/**
 * Creates a Writable stream that stores written chunks into the provided array.
 *
 * @param {Array<string|Buffer>} sink
 * @param {object} [options]
 * @returns {Writable}
 */
function createMemoryWritable(sink = [], options = {}) {
  return new Writable({
    ...options,
    write(chunk, encoding, callback) {
      sink.push(chunk.toString());
      callback();
    },
  });
}

/**
 * Creates an object-mode Writable stream that stores written objects into the provided array.
 *
 * @param {Array<any>} sink
 * @returns {Writable}
 */
function createObjectWritable(sink = []) {
  return new Writable({
    objectMode: true,
    write(chunk, encoding, callback) {
      sink.push(chunk);
      callback();
    },
  });
}

module.exports = {
  Writable,
  createMemoryWritable,
  createObjectWritable,
};

{
  "name": "sample-readable-stream-writable",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-readable-stream-writable",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "readable-stream": "2.3.8"
      }
    },
    "node_modules/core-util-is": {
      "version": "1.0.3",
      "resolved": "https://registry.npmjs.org/core-util-is/-/core-util-is-1.0.3.tgz",
      "integrity": "sha512-ZQBvi1DcpJ4GDqanjucZ2Hj3wEO5pZDS89BWbkcrvdxksJorwUDDZamX9ldFkp9aw2lmBDLgkObEA4DWNJ9FYQ==",
      "license": "MIT"
    },
    "node_modules/inherits": {
      "version": "2.0.4",
      "resolved": "https://registry.npmjs.org/inherits/-/inherits-2.0.4.tgz",
      "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==",
      "license": "ISC"
    },
    "node_modules/isarray": {
      "version": "1.0.0",
      "resolved": "https://registry.npmjs.org/isarray/-/isarray-1.0.0.tgz",
      "integrity": "sha512-VLghIWNM6ELQzo7zwmcg0NmTVyWKYjvIeM83yjp0wRDTmUnrM678fQbcKBo6n2CJEF0szoG//ytg+TKla89ALQ==",
      "license": "MIT"
    },
    "node_modules/process-nextick-args": {
      "version": "2.0.1",
      "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.1.tgz",
      "integrity": "sha512-3ouUOpQhtgrbOa17J7+uxOTpITYWaGP7/AhoR3+A+/1e9skrzelGi/dXzEYyvbxubEF6Wn2ypscTKiKJFFn1ag==",
      "license": "MIT"
    },
    "node_modules/readable-stream": {
      "version": "2.3.8",
      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.8.tgz",
      "integrity": "sha512-8p0AUk4XODgIewSi0l8Epjs+EVnWiK7NoDIEGU0HhE7+ZyY8D1IMY7odu5lRrFXGg71L15KG8QrPmum45RTtdA==",
      "license": "MIT",
      "dependencies": {
        "core-util-is": "~1.0.0",
        "inherits": "~2.0.3",
        "isarray": "~1.0.0",
        "process-nextick-args": "~2.0.0",
        "safe-buffer": "~5.1.1",
        "string_decoder": "~1.1.1",
        "util-deprecate": "~1.0.1"
      }
    },
    "node_modules/safe-buffer": {
      "version": "5.1.2",
      "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.1.2.tgz",
      "integrity": "sha512-Gd2UZBJDkXlY7GbJxfsE8/nvKkUEU1G38c1siN6QP6a9PT9MmHB8GnpscSmMJSoF8LOIrt8ud/wPtojys4G6+g==",
      "license": "MIT"
    },
    "node_modules/string_decoder": {
      "version": "1.1.1",
      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.1.1.tgz",
      "integrity": "sha512-n/ShnvDi6FHbbVfviro+WojiFzv+s8MPMHBczVePfUpDJLwoLT0ht1l4YwBCbi8pJAveEEdnkHyPyTP/mzRfwg==",
      "license": "MIT",
      "dependencies": {
        "safe-buffer": "~5.1.0"
      }
    },
    "node_modules/util-deprecate": {
      "version": "1.0.2",
      "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
      "integrity": "sha512-EPD5q1uXyFxJpCrLnCc1nHnq3gOa6DZBocAIiI2TaSCA7VCJ1UJDMagCzIkXNsUYfD1daK//LTEQ8xiIbrHtcw==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-readable-stream-writable",
  "version": "1.0.0",
  "description": "Verify readable-stream Writable stream implementation and data writing",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "readable-stream": "2.3.8"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify readable-stream.Writable in pkg:npm/readable-stream@2.3.8",
  "kind": "HOW",
  "packages": [
    "pkg:npm/readable-stream@2.3.8"
  ],
  "symbols": [
    "readable-stream.Writable"
  ]
}

const assert = require('node:assert');
const { Writable, createMemoryWritable, createObjectWritable } = require('../index.js');

async function main() {
  // 1. Writable stream buffers and processes written chunks and emits finish event on end
  {
    const sink = [];
    const writable = createMemoryWritable(sink);

    writable.write('chunk-1');
    writable.write('chunk-2');

    await new Promise((resolve, reject) => {
      writable.on('finish', resolve);
      writable.on('error', reject);
      writable.end('chunk-3');
    });

    assert.deepStrictEqual(sink, ['chunk-1', 'chunk-2', 'chunk-3']);
  }

  // 2. Writable stream write method invokes callback upon successful chunk processing
  {
    const sink = [];
    const writable = createMemoryWritable(sink);

    await new Promise((resolve, reject) => {
      writable.write('step-a', (err1) => {
        if (err1) return reject(err1);
        writable.write('step-b', (err2) => {
          if (err2) return reject(err2);
          writable.end(resolve);
        });
      });
    });

    assert.deepStrictEqual(sink, ['step-a', 'step-b']);
  }

  // 3. Writable stream with objectMode accepts and collects arbitrary JavaScript objects
  {
    const sink = [];
    const writable = createObjectWritable(sink);
    const item1 = { id: 101, status: 'pending' };
    const item2 = { id: 102, status: 'completed' };

    await new Promise((resolve, reject) => {
      writable.write(item1);
      writable.write(item2);
      writable.on('finish', resolve);
      writable.on('error', reject);
      writable.end();
    });

    assert.deepStrictEqual(sink, [item1, item2]);
  }

  console.log('Contract test passed successfully.');
}

main().catch((err) => {
  console.error(err);
  process.exit(1);
});