fast-csv 5.0.5: format

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 format in pkg:npm/fast-csv@5.0.5
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/fast-csv@5.0.5
Demonstrate these symbols/APIs:
  - format

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:sha256:84708170ec6cc598fd510f45ec3532bec547355ac5ee660132e95f6459e27315","contract":["format returns a CsvFormatterStream transform stream instance","format serializes rows from array data without headers","format serializes row objects and auto-discovers headers from first object","format serializes objects with explicit custom headers order","format applies custom delimiter, quote, and quoteColumns options","format transforms rows using a synchronous transform function","format supports custom rowDelimiter and includeEndRowDelimiter","format handles writeBOM option to prepend UTF-8 byte order mark"],"goal":"verify format in pkg:npm/fast-csv@5.0.5","kind":"HOW","packages":["pkg:npm/fast-csv@5.0.5"],"schemaVersion":1,"symbols":["format"]},"contractCommand":["node","test/contract.cjs"],"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/fast-csv@5.0.5"],"schemaVersion":1,"subject":"pkg:npm/fast-csv@5.0.5","symbols":["format"],"verifierAdapter":"node-typescript@1"}

const { format, CsvFormatterStream } = require('fast-csv');

function createFormatter(options) {
  return format(options);
}

async function formatRows(rows, options = {}) {
  return new Promise((resolve, reject) => {
    const stream = format(options);
    const chunks = [];
    stream.on('data', (chunk) => chunks.push(chunk));
    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
    stream.on('error', reject);
    for (const row of rows) {
      stream.write(row);
    }
    stream.end();
  });
}

module.exports = {
  format,
  CsvFormatterStream,
  createFormatter,
  formatRows,
};

{
  "name": "sample-fast-csv-format",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-fast-csv-format",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "fast-csv": "5.0.5"
      }
    },
    "node_modules/@fast-csv/format": {
      "version": "5.0.5",
      "resolved": "https://registry.npmjs.org/@fast-csv/format/-/format-5.0.5.tgz",
      "integrity": "sha512-0P9SJXXnqKdmuWlLaTelqbrfdgN37Mvrb369J6eNmqL41IEIZQmV4sNM4GgAK2Dz3aH04J0HKGDMJFkYObThTw==",
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        "lodash.isfunction": "^3.0.9",
        "lodash.isnil": "^4.0.0"
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    },
    "node_modules/@fast-csv/parse": {
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      "resolved": "https://registry.npmjs.org/@fast-csv/parse/-/parse-5.0.5.tgz",
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        "lodash.groupby": "^4.6.0",
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        "lodash.isnil": "^4.0.0",
        "lodash.isundefined": "^3.0.1",
        "lodash.uniq": "^4.5.0"
      }
    },
    "node_modules/fast-csv": {
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      "resolved": "https://registry.npmjs.org/fast-csv/-/fast-csv-5.0.5.tgz",
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      "license": "MIT",
      "dependencies": {
        "@fast-csv/format": "5.0.5",
        "@fast-csv/parse": "5.0.5"
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      "license": "MIT"
    }
  }
}

{
  "name": "sample-fast-csv-format",
  "version": "1.0.0",
  "description": "Minimal clean-room sample verifying format in fast-csv",
  "main": "index.js",
  "license": "MIT-0",
  "dependencies": {
    "fast-csv": "5.0.5"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify format in pkg:npm/fast-csv@5.0.5",
  "kind": "HOW",
  "packages": [
    "pkg:npm/fast-csv@5.0.5"
  ],
  "symbols": [
    "format"
  ]
}

const assert = require('node:assert/strict');
const { format, CsvFormatterStream, createFormatter, formatRows } = require('../index.js');

async function main() {
  // 1. format returns a CsvFormatterStream transform stream instance
  {
    const stream = format();
    assert.ok(stream instanceof CsvFormatterStream);
    const created = createFormatter();
    assert.ok(created instanceof CsvFormatterStream);
  }

  // 2. format serializes rows from array data without headers
  {
    const rows = [
      ['a', 'b', 'c'],
      ['1', '2', '3'],
    ];
    const result = await formatRows(rows, { headers: false });
    assert.equal(result, 'a,b,c\n1,2,3');
  }

  // 3. format serializes row objects and auto-discovers headers from first object
  {
    const rows = [
      { id: 1, name: 'alpha' },
      { id: 2, name: 'beta' },
    ];
    const result = await formatRows(rows, { headers: true });
    assert.equal(result, 'id,name\n1,alpha\n2,beta');
  }

  // 4. format serializes objects with explicit custom headers order
  {
    const rows = [{ id: 1, name: 'alpha' }];
    const result = await formatRows(rows, { headers: ['name', 'id'] });
    assert.equal(result, 'name,id\nalpha,1');
  }

  // 5. format applies custom delimiter, quote, and quoteColumns options
  {
    const rows = [{ key: 'k1', value: 'v1' }];
    const result = await formatRows(rows, {
      delimiter: ';',
      quote: '"',
      quoteColumns: { value: true },
      quoteHeaders: false,
      headers: ['key', 'value'],
    });
    assert.equal(result, 'key;value\nk1;"v1"');
  }

  // 6. format transforms rows using a synchronous transform function
  {
    const rows = [['test', 5]];
    const result = await formatRows(rows, {
      headers: false,
      transform: (row) => [row[0].toUpperCase(), row[1] * 2],
    });
    assert.equal(result, 'TEST,10');
  }

  // 7. format supports custom rowDelimiter and includeEndRowDelimiter
  {
    const rows = [
      ['r1', 'c1'],
      ['r2', 'c2'],
    ];
    const result = await formatRows(rows, {
      headers: false,
      rowDelimiter: '\r\n',
      includeEndRowDelimiter: true,
    });
    assert.equal(result, 'r1,c1\r\nr2,c2\r\n');
  }

  // 8. format handles writeBOM option to prepend UTF-8 byte order mark
  {
    const rows = [['col1', 'col2']];
    const result = await formatRows(rows, {
      headers: false,
      writeBOM: true,
    });
    assert.equal(result, '\ufeffcol1,col2');
  }

  console.log('All contract assertions passed.');
}

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