@eslint/eslintrc 3.3.6: Resolve legacy ESLint configuration hierarchy using Legacy.ConfigArrayFactory

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: Resolve legacy ESLint configuration hierarchy using Legacy.ConfigArrayFactory
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40eslint/eslintrc@3.3.6
Demonstrate these symbols/APIs:
  - Legacy.ConfigArray
  - Legacy.ConfigArrayFactory

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:dce1c94c46e6ab426f13033f0707a9ac9c57d65ee561f6c4ea092e298347c349","contract":["ConfigArrayFactory initializes and creates ConfigArray instances from raw configuration data","ConfigArray exposes isRoot indicating whether root configuration is set","extractConfig resolves merged rules and globals for target file paths","extractConfig applies override blocks to matching target file patterns"],"goal":"Resolve legacy ESLint configuration hierarchy using Legacy.ConfigArrayFactory","kind":"HOW","packages":["pkg:npm/%40eslint/eslintrc@3.3.6"],"schemaVersion":1,"symbols":["Legacy.ConfigArray","Legacy.ConfigArrayFactory"]},"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","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40eslint/eslintrc@3.3.6"],"schemaVersion":1,"subject":"pkg:npm/%40eslint/eslintrc@3.3.6","symbols":["Legacy.ConfigArray","Legacy.ConfigArrayFactory"],"verifierAdapter":"node-typescript@1"}

'use strict';

const path = require('node:path');
const { Legacy } = require('@eslint/eslintrc');

/**
 * Creates a ConfigArray from configuration data using ConfigArrayFactory.
 * @param {Object} configData - ESLint configuration object.
 * @param {Object} [options] - Factory options including basePath.
 * @returns {Legacy.ConfigArray}
 */
function createConfigArray(configData, options = {}) {
  const basePath = options.basePath || process.cwd();
  const factory = new Legacy.ConfigArrayFactory({ basePath, ...options });
  return factory.create(configData, { basePath, ...options });
}

/**
 * Resolves the configuration for a specific target file path.
 * @param {Legacy.ConfigArray} configArray - The ConfigArray instance.
 * @param {string} filePath - Absolute path to the file.
 * @returns {Object} Extracted configuration for the file.
 */
function resolveConfigForFile(configArray, filePath) {
  const absolutePath = path.isAbsolute(filePath) ? filePath : path.resolve(filePath);
  return configArray.extractConfig(absolutePath);
}

module.exports = {
  Legacy,
  createConfigArray,
  resolveConfigForFile
};

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  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
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      "name": "sample-eslint-eslintrc-legacy",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "@eslint/eslintrc": "3.3.6"
      }
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{
  "name": "sample-eslint-eslintrc-legacy",
  "version": "1.0.0",
  "description": "Resolve legacy ESLint configuration hierarchy using Legacy.ConfigArrayFactory",
  "main": "index.js",
  "type": "commonjs",
  "scripts": {
    "test": "node test/contract.cjs"
  },
  "license": "MIT-0",
  "dependencies": {
    "@eslint/eslintrc": "3.3.6"
  }
}

{
  "schemaVersion": 1,
  "goal": "Resolve legacy ESLint configuration hierarchy using Legacy.ConfigArrayFactory",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40eslint/eslintrc@3.3.6"
  ],
  "symbols": [
    "Legacy.ConfigArray",
    "Legacy.ConfigArrayFactory"
  ]
}

'use strict';

const assert = require('node:assert/strict');
const path = require('node:path');
const { Legacy, createConfigArray, resolveConfigForFile } = require('../index.js');

// 1. ConfigArrayFactory initializes and creates ConfigArray instances from raw configuration data
const factory = new Legacy.ConfigArrayFactory({ basePath: __dirname });
assert.ok(factory instanceof Legacy.ConfigArrayFactory, 'factory must be an instance of ConfigArrayFactory');

const rawConfig = {
  root: true,
  env: { browser: true, es2021: true },
  rules: {
    'no-unused-vars': 'warn',
    semi: ['error', 'always']
  },
  globals: {
    customGlobal: 'readonly'
  },
  overrides: [
    {
      files: ['*.spec.js', '*.test.js'],
      rules: {
        'no-unused-vars': 'off'
      }
    }
  ]
};

const configArray = factory.create(rawConfig, { basePath: __dirname, name: 'inline-test-config' });
assert.ok(configArray instanceof Legacy.ConfigArray, 'configArray must be an instance of ConfigArray');

const helperArray = createConfigArray(rawConfig, { basePath: __dirname });
assert.ok(helperArray instanceof Legacy.ConfigArray, 'createConfigArray helper must return a ConfigArray');

// 2. ConfigArray exposes isRoot indicating whether root configuration is set
assert.strictEqual(configArray.isRoot(), true, 'isRoot must return true when root: true is configured');

const nonRootArray = factory.create({ rules: { eqeqeq: 'error' } }, { basePath: __dirname });
assert.strictEqual(nonRootArray.isRoot(), false, 'isRoot must return false when root is not set');

// 3. extractConfig resolves merged rules and globals for target file paths
const targetSource = path.resolve(__dirname, '../src/app.js');
const sourceConfig = configArray.extractConfig(targetSource);

assert.ok(sourceConfig, 'extracted config for source file must exist');
assert.ok(sourceConfig.rules, 'extracted config must contain rules');
assert.deepStrictEqual(sourceConfig.rules['no-unused-vars'], ['warn'], 'no-unused-vars rule must be configured as warn');
assert.deepStrictEqual(sourceConfig.rules.semi, ['error', 'always'], 'semi rule must match configuration');
assert.strictEqual(sourceConfig.globals.customGlobal, 'readonly', 'custom global must be resolved');

const helperResolved = resolveConfigForFile(configArray, targetSource);
assert.deepStrictEqual(helperResolved.rules['no-unused-vars'], ['warn'], 'helper resolution must match direct extractConfig');

// 4. extractConfig applies override blocks to matching target file patterns
const targetTest = path.resolve(__dirname, '../src/app.test.js');
const testConfig = configArray.extractConfig(targetTest);

assert.ok(testConfig, 'extracted config for test file must exist');
assert.deepStrictEqual(testConfig.rules['no-unused-vars'], ['off'], 'overrides must turn off no-unused-vars in test files');
assert.deepStrictEqual(testConfig.rules.semi, ['error', 'always'], 'un-overridden rules must remain active');

console.log('Contract verification succeeded.');