js-yaml 4.1.0: Schema

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 js-yaml.Schema in pkg:npm/js-yaml@4.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/js-yaml@4.1.0
Demonstrate these symbols/APIs:
  - js-yaml.Schema
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:49e7986e3830f5671e94e65545f4eeb60ad5ba9eae0872ea5f12d5264d5b24c1","constraints":{"executionContext":"node"},"contract":["new yaml.Schema(type) instantiates a custom Schema containing the explicit Type","yaml.DEFAULT_SCHEMA.extend(type) creates a new Schema inheriting default types with added custom explicit Type","yaml.DEFAULT_SCHEMA.extend([type1, type2]) creates a new Schema with multiple custom explicit Types","yaml.DEFAULT_SCHEMA.extend({ implicit: [type] }) extends schema with custom implicit scalar Type","yaml.load with extended Schema deserializes custom explicit tags into instantiated objects","yaml.dump with extended Schema serializes custom objects with custom tag notation","yaml.load with extended Schema resolves custom implicit scalar types automatically","yaml.DEFAULT_SCHEMA.extend throws YAMLException when given invalid type definitions"],"goal":"verify js-yaml.Schema in pkg:npm/js-yaml@4.1.0","kind":"HOW","packages":["pkg:npm/js-yaml@4.1.0"],"schemaVersion":1,"symbols":["js-yaml.Schema"]},"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/js-yaml@4.1.0"],"schemaVersion":1,"subject":"pkg:npm/js-yaml@4.1.0","symbols":["js-yaml.Schema"],"verifierAdapter":"node-typescript@1"}

{
  "name": "js-yaml-schema-verification",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "js-yaml-schema-verification",
      "version": "1.0.0",
      "dependencies": {
        "js-yaml": "4.1.0"
      }
    },
    "node_modules/argparse": {
      "version": "2.0.1",
      "resolved": "https://registry.npmjs.org/argparse/-/argparse-2.0.1.tgz",
      "integrity": "sha512-8+9WqebbFzpX9OR+Wa6O29asIogeRMzcGtAINdpMHHyAg10f05aSFVBbcEqGf/PXw1EjAZ+q2/bEBg3DvurK3Q==",
      "license": "Python-2.0"
    },
    "node_modules/js-yaml": {
      "version": "4.1.0",
      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.1.0.tgz",
      "integrity": "sha512-wpxZs9NoxZaJESJGIZTyDEaYpl0FKSA+FB9aJiyemKhMwkxQg63h4T1KJgUGHpTqPDNRcmmYLugrRjJlBtWvRA==",
      "license": "MIT",
      "dependencies": {
        "argparse": "^2.0.1"
      },
      "bin": {
        "js-yaml": "bin/js-yaml.js"
      }
    }
  }
}

{
  "name": "js-yaml-schema-verification",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for js-yaml.Schema",
  "dependencies": {
    "js-yaml": "4.1.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify js-yaml.Schema in pkg:npm/js-yaml@4.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/js-yaml@4.1.0"
  ],
  "symbols": [
    "js-yaml.Schema"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const assert = require('node:assert');
const yaml = require('js-yaml');

// Helper classes for custom types
class Point {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
}

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}

const PointType = new yaml.Type('!point', {
  kind: 'mapping',
  resolve: function(data) {
    return data !== null && typeof data === 'object' && typeof data.x === 'number' && typeof data.y === 'number';
  },
  construct: function(data) {
    return new Point(data.x, data.y);
  },
  instanceOf: Point,
  represent: function(point) {
    return { x: point.x, y: point.y };
  }
});

const PersonType = new yaml.Type('!person', {
  kind: 'mapping',
  resolve: function(data) {
    return data !== null && typeof data === 'object' && typeof data.name === 'string' && typeof data.age === 'number';
  },
  construct: function(data) {
    return new Person(data.name, data.age);
  },
  instanceOf: Person,
  represent: function(person) {
    return { name: person.name, age: person.age };
  }
});

const HexType = new yaml.Type('!hex', {
  kind: 'scalar',
  resolve: function(data) {
    return typeof data === 'string' && /^0x[0-9a-fA-F]+$/.test(data);
  },
  construct: function(data) {
    return parseInt(data, 16);
  },
  predicate: function(data) {
    return typeof data === 'number';
  },
  represent: function(data) {
    return '0x' + data.toString(16);
  }
});

const RegexType = new yaml.Type('!regex', {
  kind: 'scalar',
  resolve: function(data) {
    return typeof data === 'string' && data.startsWith('/') && data.endsWith('/');
  },
  construct: function(data) {
    return new RegExp(data.slice(1, -1));
  }
});

// 1. new yaml.Schema(type) instantiates a custom Schema containing the explicit Type
const standaloneSchema = new yaml.Schema(PointType);
assert.ok(standaloneSchema instanceof yaml.Schema);
assert.ok(Array.isArray(standaloneSchema.explicit));
assert.ok(standaloneSchema.explicit.includes(PointType));

// 2. yaml.DEFAULT_SCHEMA.extend(type) creates a new Schema inheriting default types with added custom explicit Type
const pointSchema = yaml.DEFAULT_SCHEMA.extend(PointType);
assert.ok(pointSchema instanceof yaml.Schema);
assert.notStrictEqual(pointSchema, yaml.DEFAULT_SCHEMA);

// 3. yaml.DEFAULT_SCHEMA.extend([type1, type2]) creates a new Schema with multiple custom explicit Types
const multiSchema = yaml.DEFAULT_SCHEMA.extend([PointType, PersonType, HexType]);
assert.ok(multiSchema instanceof yaml.Schema);

// 4. yaml.DEFAULT_SCHEMA.extend({ implicit: [type] }) extends schema with custom implicit scalar Type
const implicitSchema = yaml.DEFAULT_SCHEMA.extend({ implicit: [RegexType] });
assert.ok(implicitSchema instanceof yaml.Schema);
assert.ok(implicitSchema.implicit.includes(RegexType));

// 5. yaml.load with extended Schema deserializes custom explicit tags into instantiated objects
const pointYaml = 'location: !point\n  x: 15\n  y: 30';
const loadedPoint = yaml.load(pointYaml, { schema: pointSchema });
assert.ok(loadedPoint.location instanceof Point);
assert.strictEqual(loadedPoint.location.x, 15);
assert.strictEqual(loadedPoint.location.y, 30);

const multiYaml = `
user: !person
  name: Alice
  age: 28
address: !point
  x: 100
  y: 200
flags: !hex 0x2a
`;
const loadedMulti = yaml.load(multiYaml, { schema: multiSchema });
assert.ok(loadedMulti.user instanceof Person);
assert.strictEqual(loadedMulti.user.name, 'Alice');
assert.strictEqual(loadedMulti.user.age, 28);
assert.ok(loadedMulti.address instanceof Point);
assert.strictEqual(loadedMulti.flags, 42);

// 6. yaml.dump with extended Schema serializes custom objects with custom tag notation
const pointDumped = yaml.dump({ location: new Point(15, 30) }, { schema: pointSchema });
assert.ok(pointDumped.includes('!point'));
const reloaded = yaml.load(pointDumped, { schema: pointSchema });
assert.ok(reloaded.location instanceof Point);
assert.strictEqual(reloaded.location.x, 15);
assert.strictEqual(reloaded.location.y, 30);

// 7. yaml.load with extended Schema resolves custom implicit scalar types automatically
const regexYaml = 'pattern: /abc[0-9]+/';
const loadedRegex = yaml.load(regexYaml, { schema: implicitSchema });
assert.ok(loadedRegex.pattern instanceof RegExp);
assert.ok(loadedRegex.pattern.test('abc1234'));

// 8. yaml.DEFAULT_SCHEMA.extend throws YAMLException when given invalid type definitions
assert.throws(() => {
  yaml.DEFAULT_SCHEMA.extend('not-a-type');
}, yaml.YAMLException);

assert.throws(() => {
  yaml.DEFAULT_SCHEMA.extend([{ invalid: true }]);
}, yaml.YAMLException);

console.log('Contract passed');