eslint-visitor-keys 5.0.1

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/eslint-visitor-keys@5.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/eslint-visitor-keys@5.0.1

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:sha256:667c4dea2cc14e2fb141d505db81b55cb1cde35e830bb50d519cb8d2ff7b82d5","contract":["KEYS defines standard visitor keys for ESTree AST node types","getKeys extracts property keys from an AST node excluding blacklisted and private underscore properties","unionWith creates a new frozen keys dictionary with additional custom node types merged without duplicate entries","unionWith preserves immutability of the original KEYS object"],"goal":"verify pkg:npm/eslint-visitor-keys@5.0.1","kind":"HOW","packages":["pkg:npm/eslint-visitor-keys@5.0.1"],"schemaVersion":1},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/eslint-visitor-keys@5.0.1"],"schemaVersion":1,"subject":"pkg:npm/eslint-visitor-keys@5.0.1","verifierAdapter":"node-typescript@1"}

{
  "name": "sample-eslint-visitor-keys",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-eslint-visitor-keys",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "eslint-visitor-keys": "5.0.1"
      }
    },
    "node_modules/eslint-visitor-keys": {
      "version": "5.0.1",
      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-5.0.1.tgz",
      "integrity": "sha512-tD40eHxA35h0PEIZNeIjkHoDR4YjjJp34biM0mDvplBe//mB+IHCqHDGV7pxF+7MklTvighcCPPZC7ynWyjdTA==",
      "license": "Apache-2.0",
      "engines": {
        "node": "^20.19.0 || ^22.13.0 || >=24"
      },
      "funding": {
        "url": "https://opencollective.com/eslint"
      }
    }
  }
}

{
  "name": "sample-eslint-visitor-keys",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "eslint-visitor-keys": "5.0.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/eslint-visitor-keys@5.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/eslint-visitor-keys@5.0.1"
  ]
}

import assert from 'node:assert/strict';
import { KEYS, getKeys, unionWith } from 'eslint-visitor-keys';

// 1. KEYS defines standard visitor keys for ESTree AST node types
assert.deepEqual(KEYS.BinaryExpression, ['left', 'right']);
assert.deepEqual(KEYS.IfStatement, ['test', 'consequent', 'alternate']);
assert.deepEqual(KEYS.Program, ['body']);
assert.deepEqual(KEYS.Identifier, []);
assert.deepEqual(KEYS.Literal, []);
assert.equal(typeof KEYS, 'object');

// 2. getKeys extracts property keys from an AST node excluding blacklisted and private underscore properties
const astNode = {
  type: 'BinaryExpression',
  left: { type: 'Identifier', name: 'a' },
  right: { type: 'Literal', value: 1 },
  parent: { type: 'Program' },
  leadingComments: [{ type: 'Line', value: ' comment' }],
  trailingComments: [],
  _internalMetadata: 'ignored'
};
const extractedKeys = getKeys(astNode);
assert.deepEqual(extractedKeys, ['type', 'left', 'right']);

// 3. unionWith creates a new frozen keys dictionary with additional custom node types merged without duplicate entries
const extendedKeys = unionWith({
  CustomNode: ['child', 'extra'],
  BinaryExpression: ['metadata']
});
assert.deepEqual(extendedKeys.CustomNode, ['child', 'extra']);
assert.deepEqual(extendedKeys.BinaryExpression, ['metadata', 'left', 'right']);
assert.ok(Object.isFrozen(extendedKeys));
assert.ok(Object.isFrozen(extendedKeys.CustomNode));
assert.ok(Object.isFrozen(extendedKeys.BinaryExpression));

// 4. unionWith preserves immutability of the original KEYS object
assert.deepEqual(KEYS.BinaryExpression, ['left', 'right']);
assert.equal(KEYS.CustomNode, undefined);