yaml 2.9.1: parse, stringify

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 pkg:npm/yaml@2.9.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/yaml@2.9.1

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:c7aca94948f71fdfc0e1f7dbc2ab7113abeffddcbc86e47a8e03ee08821393fc","constraints":{"executionContext":"node"},"contract":["YAML.parse parses YAML scalar values into JavaScript primitives","YAML.parse parses nested YAML mappings and sequences into JavaScript objects and arrays","YAML.stringify serializes JavaScript objects into formatted YAML strings","YAML.parse supports reviver function to transform parsed values","YAML.parse throws an error when parsing invalid YAML syntax"],"goal":"verify pkg:npm/yaml@2.9.1","kind":"HOW","packages":["pkg:npm/yaml@2.9.1"],"schemaVersion":1,"symbols":["YAML.parse","YAML.stringify"]},"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/yaml@2.9.1"],"schemaVersion":1,"subject":"pkg:npm/yaml@2.9.1","symbols":["YAML.parse","YAML.stringify"],"verifierAdapter":"node-typescript@1"}

const YAML = require('yaml');

/**
 * Parse a YAML string into a JavaScript data structure.
 * @param {string} yamlString - The YAML content to parse.
 * @param {Function|object} [reviverOrOptions] - Optional reviver function or options object.
 * @returns {any} The parsed JavaScript value.
 */
function parseYaml(yamlString, reviverOrOptions) {
  return YAML.parse(yamlString, reviverOrOptions);
}

/**
 * Stringify a JavaScript value into a YAML string.
 * @param {any} value - The JavaScript value to stringify.
 * @param {Function|object} [replacerOrOptions] - Optional replacer function or options object.
 * @returns {string} The formatted YAML string.
 */
function stringifyYaml(value, replacerOrOptions) {
  return YAML.stringify(value, replacerOrOptions);
}

module.exports = {
  parseYaml,
  stringifyYaml,
  YAML,
};

{
  "name": "sample-yaml",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-yaml",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "yaml": "2.9.1"
      }
    },
    "node_modules/yaml": {
      "version": "2.9.1",
      "resolved": "https://registry.npmjs.org/yaml/-/yaml-2.9.1.tgz",
      "integrity": "sha512-3NxN8+78OdzbT7C/WjGsyfPAtJaN3FNDsWxv7Y7mcDsT/oOmgW8BpyQQFFBnvZE3j9Y2Sdz1ULFLezL7Eb2yFw==",
      "license": "ISC",
      "bin": {
        "yaml": "bin.mjs"
      },
      "engines": {
        "node": ">= 14.6"
      },
      "funding": {
        "url": "https://github.com/sponsors/eemeli"
      }
    }
  }
}

{
  "name": "sample-yaml",
  "version": "1.0.0",
  "description": "verify pkg:npm/yaml@2.9.1",
  "main": "index.js",
  "license": "MIT-0",
  "dependencies": {
    "yaml": "2.9.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/yaml@2.9.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/yaml@2.9.1"
  ],
  "symbols": [
    "YAML.parse",
    "YAML.stringify"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert/strict';
import YAML from 'yaml';
import pkg from '../index.js';

const { parseYaml, stringifyYaml } = pkg;

// 1. YAML.parse parses YAML scalar values into JavaScript primitives
{
  const num = parseYaml('42');
  assert.equal(num, 42);

  const floatVal = parseYaml('3.14159');
  assert.equal(floatVal, 3.14159);

  const str = parseYaml('hello world');
  assert.equal(str, 'hello world');

  const boolVal = parseYaml('true');
  assert.equal(boolVal, true);

  const nullVal = parseYaml('null');
  assert.equal(nullVal, null);
}

// 2. YAML.parse parses nested YAML mappings and sequences into JavaScript objects and arrays
{
  const yamlText = `
name: yaml-sample
version: 1.0.0
tags:
  - config
  - parser
settings:
  enabled: true
  retries: 3
`;
  const parsed = parseYaml(yamlText);
  assert.deepEqual(parsed, {
    name: 'yaml-sample',
    version: '1.0.0',
    tags: ['config', 'parser'],
    settings: {
      enabled: true,
      retries: 3
    }
  });
}

// 3. YAML.stringify serializes JavaScript objects into formatted YAML strings
{
  const data = {
    service: 'auth',
    port: 8080,
    endpoints: ['/login', '/logout']
  };
  const yamlText = stringifyYaml(data);
  const roundTrip = parseYaml(yamlText);
  assert.deepEqual(roundTrip, data);
}

// 4. YAML.parse supports reviver function to transform parsed values
{
  const yamlText = `
price: 50
tax: 5
`;
  const parsed = YAML.parse(yamlText, (key, value) => {
    if (typeof value === 'number') {
      return value * 2;
    }
    return value;
  });
  assert.deepEqual(parsed, {
    price: 100,
    tax: 10
  });
}

// 5. YAML.parse throws an error when parsing invalid YAML syntax
{
  const invalidYaml = `
unclosed: [1, 2,
mapping: {
`;
  assert.throws(
    () => {
      parseYaml(invalidYaml);
    },
    (err) => err instanceof Error
  );
}

console.log('All contract tests passed.');