eslint-visitor-keys 4.2.1

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@4.2.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/eslint-visitor-keys@4.2.1
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:e713a2f9f5953d613d7a08f2ae11919837da0490ce25fd3ee8d1104dcb261642","constraints":{"executionContext":"node"},"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@4.2.1","kind":"HOW","packages":["pkg:npm/eslint-visitor-keys@4.2.1"],"schemaVersion":1},"contractCommand":["node","test/contract.js"],"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/eslint-visitor-keys@4.2.1"],"schemaVersion":1,"subject":"pkg:npm/eslint-visitor-keys@4.2.1","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": "4.2.1"
      }
    },
    "node_modules/eslint-visitor-keys": {
      "version": "4.2.1",
      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-4.2.1.tgz",
      "integrity": "sha512-Uhdk5sfqcee/9H/rCOJikYz67o0a2Tw2hGRPOG2Y1R2dg7brRe1uG0yaNQDHu+TO/uQPF/5eCapvYSmHUjt7JQ==",
      "license": "Apache-2.0",
      "engines": {
        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
      },
      "funding": {
        "url": "https://opencollective.com/eslint"
      }
    }
  }
}

{
  "name": "sample-eslint-visitor-keys",
  "version": "1.0.0",
  "private": true,
  "license": "MIT-0",
  "dependencies": {
    "eslint-visitor-keys": "4.2.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/eslint-visitor-keys@4.2.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/eslint-visitor-keys@4.2.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const { KEYS, getKeys, unionWith } = require("eslint-visitor-keys");

function getNodeKeys(node) {
  return getKeys(node);
}

function extendVisitorKeys(additionalKeys) {
  return unionWith(additionalKeys);
}

module.exports = {
  KEYS,
  getNodeKeys,
  extendVisitorKeys,
  getKeys,
  unionWith
};

const assert = require("node:assert/strict");
const { KEYS, getKeys, unionWith } = require("eslint-visitor-keys");

// Contract 1: KEYS defines standard visitor keys for ESTree AST node types
assert.ok(typeof KEYS === "object" && KEYS !== null, "KEYS must be an object");
assert.ok(Array.isArray(KEYS.ArrayExpression), "KEYS.ArrayExpression must be an array");
assert.deepEqual(KEYS.ArrayExpression, ["elements"]);
assert.deepEqual(KEYS.BinaryExpression, ["left", "right"]);
assert.deepEqual(KEYS.Program, ["body"]);
assert.ok(Object.isFrozen(KEYS), "KEYS must be frozen");
assert.ok(Object.isFrozen(KEYS.ArrayExpression), "KEYS.ArrayExpression must be frozen");

// Contract 2: getKeys extracts property keys from an AST node excluding blacklisted and private underscore properties
const testNode = {
  type: "Identifier",
  name: "foo",
  parent: { type: "Program" },
  leadingComments: [{ value: "comment" }],
  trailingComments: [{ value: "comment" }],
  _privateProp: 123,
  loc: { start: 0, end: 3 }
};
const extractedKeys = getKeys(testNode);
assert.ok(extractedKeys.includes("type"), "type should be included");
assert.ok(extractedKeys.includes("name"), "name should be included");
assert.ok(extractedKeys.includes("loc"), "loc should be included");
assert.strictEqual(extractedKeys.includes("parent"), false, "parent should be excluded");
assert.strictEqual(extractedKeys.includes("leadingComments"), false, "leadingComments should be excluded");
assert.strictEqual(extractedKeys.includes("trailingComments"), false, "trailingComments should be excluded");
assert.strictEqual(extractedKeys.includes("_privateProp"), false, "private underscore properties should be excluded");

// Contract 3: unionWith creates a new frozen keys dictionary with additional custom node types merged without duplicate entries
const customKeys = {
  CustomType: ["customChild"],
  BinaryExpression: ["left", "right", "extra"]
};
const mergedKeys = unionWith(customKeys);
assert.ok(Object.isFrozen(mergedKeys), "mergedKeys must be frozen");
assert.deepEqual(mergedKeys.CustomType, ["customChild"]);
assert.ok(Object.isFrozen(mergedKeys.CustomType), "mergedKeys.CustomType must be frozen");
assert.deepEqual(mergedKeys.BinaryExpression, ["left", "right", "extra"]);
assert.ok(Object.isFrozen(mergedKeys.BinaryExpression), "mergedKeys.BinaryExpression must be frozen");

// Contract 4: unionWith preserves immutability of the original KEYS object
assert.notStrictEqual(mergedKeys, KEYS, "mergedKeys should be a new object");
assert.deepEqual(KEYS.BinaryExpression, ["left", "right"]);
assert.strictEqual(KEYS.CustomType, undefined);

console.log("All contract assertions passed successfully.");