@eslint/config-array 0.21.2: ConfigArraySymbol

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 @eslint/config-array.ConfigArraySymbol in pkg:npm/%40eslint/config-array@0.21.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40eslint/config-array@0.21.2
Demonstrate these symbols/APIs:
  - @eslint/config-array.ConfigArraySymbol

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.

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{
  "name": "verify-eslint-config-array-symbol",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "verify-eslint-config-array-symbol",
      "version": "1.0.0",
      "dependencies": {
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      }
    },
    "node_modules/@eslint/config-array": {
      "version": "0.21.2",
      "resolved": "https://registry.npmjs.org/@eslint/config-array/-/config-array-0.21.2.tgz",
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      "license": "Apache-2.0",
      "dependencies": {
        "@eslint/object-schema": "^2.1.7",
        "debug": "^4.3.1",
        "minimatch": "^3.1.5"
      },
      "engines": {
        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
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    },
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      "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-1.0.2.tgz",
      "integrity": "sha512-3oSeUO0TMV67hN1AmbXsK4yaqU7tjiHlbxRDZOpH0KW9+CeX4bRAaX0Anxt0tx2MrpRpWwQaPwIlISEJhYU5Pw==",
      "license": "MIT"
    },
    "node_modules/brace-expansion": {
      "version": "1.1.18",
      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.18.tgz",
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        "concat-map": "0.0.1"
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    "node_modules/concat-map": {
      "version": "0.0.1",
      "resolved": "https://registry.npmjs.org/concat-map/-/concat-map-0.0.1.tgz",
      "integrity": "sha512-/Srv4dswyQNBfohGpz9o6Yb3Gz3SrUDqBH5rTuhGR7ahtlbYKnVxw2bCFMRljaA7EXHaXZ8wsHdodFvbkhKmqg==",
      "license": "MIT"
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      "license": "MIT",
      "dependencies": {
        "ms": "^2.1.3"
      },
      "engines": {
        "node": ">=6.0"
      },
      "peerDependenciesMeta": {
        "supports-color": {
          "optional": true
        }
      }
    },
    "node_modules/minimatch": {
      "version": "3.1.5",
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      "license": "MIT"
    }
  }
}

{
  "name": "verify-eslint-config-array-symbol",
  "version": "1.0.0",
  "type": "module",
  "dependencies": {
    "@eslint/config-array": "0.21.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @eslint/config-array.ConfigArraySymbol in pkg:npm/%40eslint/config-array@0.21.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40eslint/config-array@0.21.2"
  ],
  "symbols": [
    "@eslint/config-array.ConfigArraySymbol"
  ]
}

import { ConfigArray, ConfigArraySymbol } from '@eslint/config-array';

/**
 * Custom ConfigArray subclass utilizing ConfigArraySymbol extension hooks.
 */
export class ExtensibleConfigArray extends ConfigArray {
  /**
   * Preprocess config items before schema validation.
   * @param {Object|string} config
   * @returns {Object}
   */
  [ConfigArraySymbol.preprocessConfig](config) {
    if (typeof config === 'string') {
      return { name: config, files: ['**/*.js'] };
    }
    return super[ConfigArraySymbol.preprocessConfig](config);
  }

  /**
   * Finalize the merged configuration object before caching and returning.
   * @param {Object} config
   * @returns {Object}
   */
  [ConfigArraySymbol.finalizeConfig](config) {
    const finalized = super[ConfigArraySymbol.finalizeConfig](config);
    return {
      ...finalized,
      finalizedBySymbol: true
    };
  }
}

export { ConfigArray, ConfigArraySymbol };

import assert from 'node:assert/strict';
import { ConfigArray, ConfigArraySymbol, ExtensibleConfigArray } from '../src/index.mjs';

// 1. ConfigArraySymbol exposes unique symbol keys for internal properties and extension methods
assert.equal(typeof ConfigArraySymbol.isNormalized, 'symbol');
assert.equal(typeof ConfigArraySymbol.configCache, 'symbol');
assert.equal(typeof ConfigArraySymbol.schema, 'symbol');
assert.equal(typeof ConfigArraySymbol.finalizeConfig, 'symbol');
assert.equal(typeof ConfigArraySymbol.preprocessConfig, 'symbol');

// 2. ConfigArraySymbol.isNormalized tracks normalization status on ConfigArray instances
const baseConfig = [
  {
    name: 'test-config',
    files: ['**/*.js']
  }
];
const arrayInstance = new ConfigArray(baseConfig, { basePath: '/workspace/test' });
assert.equal(arrayInstance[ConfigArraySymbol.isNormalized], false, 'isNormalized should initially be false');
arrayInstance.normalizeSync();
assert.equal(arrayInstance[ConfigArraySymbol.isNormalized], true, 'isNormalized should be true after normalizeSync()');

// 3. ConfigArraySymbol.configCache provides access to the internal config cache Map
const cacheMap = arrayInstance[ConfigArraySymbol.configCache];
assert.ok(cacheMap instanceof Map, 'configCache must be an instance of Map');
assert.equal(cacheMap.size, 0, 'cache should initially be empty');
const matched = arrayInstance.getConfig('/workspace/test/src/file.js');
assert.ok(matched, 'getConfig should return a configuration object');
assert.ok(cacheMap.has('/workspace/test/src/file.js'), 'configCache should contain entry after getConfig()');

// 4. ConfigArraySymbol.schema accesses the ObjectSchema instance used for validation and merging
const schemaInstance = arrayInstance[ConfigArraySymbol.schema];
assert.ok(schemaInstance, 'schema should be defined');
assert.equal(typeof schemaInstance.merge, 'function', 'schema must have merge method');
assert.equal(typeof schemaInstance.validate, 'function', 'schema must have validate method');
assert.ok(schemaInstance.hasKey('name'), 'schema must recognize base schema key name');
assert.ok(schemaInstance.hasKey('files'), 'schema must recognize base schema key files');
assert.ok(schemaInstance.hasKey('ignores'), 'schema must recognize base schema key ignores');

// 5. ConfigArraySymbol.preprocessConfig can be overridden by subclasses to transform configs during normalization
const extensible = new ExtensibleConfigArray(['shorthand-config'], { basePath: '/workspace/test' });
assert.equal(extensible[ConfigArraySymbol.isNormalized], false);
extensible.normalizeSync();
assert.equal(extensible[ConfigArraySymbol.isNormalized], true);
assert.equal(extensible.length, 1);
assert.equal(extensible[0].name, 'shorthand-config', 'shorthand string was transformed into config object with name');
assert.deepEqual(extensible[0].files, ['**/*.js'], 'shorthand string was expanded with default files pattern');

// 6. ConfigArraySymbol.finalizeConfig can be overridden by subclasses to modify the merged config returned by getConfig
const finalizedConfig = extensible.getConfig('/workspace/test/sample.js');
assert.ok(finalizedConfig, 'config should match sample.js');
assert.equal(finalizedConfig.finalizedBySymbol, true, 'finalizeConfig hook attached finalizedBySymbol flag to merged config');

console.log('All contract assertions for @eslint/config-array.ConfigArraySymbol passed successfully.');