readable-stream 2.3.8: Duplex

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.Duplex 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.Duplex

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:f9ab7d69d1ac20e966dbae9a57c201989e07104e608dce6be4bd4ac32016b1bc","contract":["Duplex stream reads queued data chunks and emits data events until end","Duplex stream writes data chunks and notifies completion via write callback","Duplex bidirectional data flow operates independently on read and write sides"],"goal":"verify readable-stream.Duplex in pkg:npm/readable-stream@2.3.8","kind":"HOW","packages":["pkg:npm/readable-stream@2.3.8"],"schemaVersion":1,"symbols":["readable-stream.Duplex"]},"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.Duplex"],"verifierAdapter":"node-typescript@1"}

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

/**
 * Creates a Duplex stream that reads from an in-memory array and records written chunks.
 *
 * @param {Array<string|Buffer>} readItems
 * @param {Array<string|Buffer>} writtenItems
 * @returns {Duplex}
 */
function createDuplexStream(readItems = [], writtenItems = []) {
  let index = 0;
  return new Duplex({
    read() {
      if (index < readItems.length) {
        this.push(readItems[index++]);
      } else {
        this.push(null);
      }
    },
    write(chunk, encoding, callback) {
      writtenItems.push(chunk.toString());
      callback();
    },
  });
}

module.exports = {
  Duplex,
  createDuplexStream,
};

{
  "name": "sample-readable-stream-duplex",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-readable-stream-duplex",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "readable-stream": "2.3.8"
      }
    },
    "node_modules/core-util-is": {
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      "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==",
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      "dependencies": {
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    "node_modules/util-deprecate": {
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      "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
      "integrity": "sha512-EPD5q1uXyFxJpCrLnCc1nHnq3gOa6DZBocAIiI2TaSCA7VCJ1UJDMagCzIkXNsUYfD1daK//LTEQ8xiIbrHtcw==",
      "license": "MIT"
    }
  }
}

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

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

const assert = require('node:assert');
const { Duplex, createDuplexStream } = require('../index.js');

async function main() {
  // 1. Duplex stream reads queued data chunks and emits data events until end
  {
    const writtenSink = [];
    const duplex = createDuplexStream(['hello', ' ', 'duplex'], writtenSink);
    const readChunks = [];

    duplex.on('data', (chunk) => {
      readChunks.push(chunk.toString());
    });

    await new Promise((resolve) => duplex.on('end', resolve));
    assert.strictEqual(readChunks.join(''), 'hello duplex');
  }

  // 2. Duplex stream writes data chunks and notifies completion via write callback
  {
    const writtenSink = [];
    const duplex = createDuplexStream([], writtenSink);

    await new Promise((resolve, reject) => {
      duplex.write('first-write', (err) => {
        if (err) return reject(err);
        duplex.write('second-write', (err2) => {
          if (err2) return reject(err2);
          duplex.end(resolve);
        });
      });
    });

    assert.deepStrictEqual(writtenSink, ['first-write', 'second-write']);
  }

  // 3. Duplex bidirectional data flow operates independently on read and write sides
  {
    const writtenSink = [];
    const duplex = createDuplexStream(['output-1', 'output-2'], writtenSink);
    const readChunks = [];

    duplex.on('data', (chunk) => {
      readChunks.push(chunk.toString());
    });

    duplex.write('input-a');
    duplex.write('input-b');
    duplex.end();

    await new Promise((resolve) => duplex.on('end', resolve));

    assert.strictEqual(readChunks.join(''), 'output-1output-2');
    assert.deepStrictEqual(writtenSink, ['input-a', 'input-b']);
  }

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

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