espree 10.4.0: VisitorKeys

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 espree.VisitorKeys in pkg:npm/espree@10.4.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/espree@10.4.0
Demonstrate these symbols/APIs:
  - espree.VisitorKeys

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:sha256:8003961f53f1d092794e03869c977b1c169d087312be9daa722f407d70a303d9","contract":["validates espree package version is 10.4.0","validates presence and structure of espree.VisitorKeys dictionary","verifies visitor keys definitions for core ESTree AST node types","traverses an ECMAScript AST using espree.VisitorKeys to visit all child nodes","handles unknown node types gracefully when querying VisitorKeys"],"goal":"verify espree.VisitorKeys in pkg:npm/espree@10.4.0","kind":"HOW","packages":["pkg:npm/espree@10.4.0"],"schemaVersion":1,"symbols":["espree.VisitorKeys"]},"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","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/espree@10.4.0"],"schemaVersion":1,"subject":"pkg:npm/espree@10.4.0","symbols":["espree.VisitorKeys"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-espree-visitor-keys",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-espree-visitor-keys",
      "version": "1.0.0",
      "dependencies": {
        "espree": "10.4.0"
      }
    },
    "node_modules/acorn": {
      "version": "8.18.0",
      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.18.0.tgz",
      "integrity": "sha512-lGq+9yr1/GuAWaVYIHRjvvySG5/4VfKIvC8EWxStPdcDh/Ka7FG3twP6v4d5BkravUilhIAsG4Qj83t02LWUPQ==",
      "license": "MIT",
      "bin": {
        "acorn": "bin/acorn"
      },
      "engines": {
        "node": ">=0.4.0"
      }
    },
    "node_modules/acorn-jsx": {
      "version": "5.3.2",
      "resolved": "https://registry.npmjs.org/acorn-jsx/-/acorn-jsx-5.3.2.tgz",
      "integrity": "sha512-rq9s+JNhf0IChjtDXxllJ7g41oZk5SlXtp0LHwyA5cejwn7vKmKp4pPri6YEePv2PU65sAsegbXtIinmDFDXgQ==",
      "license": "MIT",
      "peerDependencies": {
        "acorn": "^6.0.0 || ^7.0.0 || ^8.0.0"
      }
    },
    "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"
      }
    },
    "node_modules/espree": {
      "version": "10.4.0",
      "resolved": "https://registry.npmjs.org/espree/-/espree-10.4.0.tgz",
      "integrity": "sha512-j6PAQ2uUr79PZhBjP5C5fhl8e39FmRnOjsD5lGnWrFU8i2G776tBK7+nP8KuQUTTyAZUwfQqXAgrVH5MbH9CYQ==",
      "license": "BSD-2-Clause",
      "dependencies": {
        "acorn": "^8.15.0",
        "acorn-jsx": "^5.3.2",
        "eslint-visitor-keys": "^4.2.1"
      },
      "engines": {
        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
      },
      "funding": {
        "url": "https://opencollective.com/eslint"
      }
    }
  }
}

{
  "name": "sample-espree-visitor-keys",
  "version": "1.0.0",
  "description": "Clean-room verification sample for espree.VisitorKeys",
  "main": "test/contract.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "espree": "10.4.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify espree.VisitorKeys in pkg:npm/espree@10.4.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/espree@10.4.0"
  ],
  "symbols": [
    "espree.VisitorKeys"
  ]
}

const assert = require("assert");
const espree = require("espree");

// 1. Version validation
assert.strictEqual(espree.version, "10.4.0");

// 2. Validate espree.VisitorKeys structure and presence
assert(typeof espree.VisitorKeys === "object" && espree.VisitorKeys !== null);
const keyTypes = Object.keys(espree.VisitorKeys);
assert(keyTypes.length > 50, "VisitorKeys should define visitor keys for standard ESTree node types");

// 3. Verify specific visitor keys definitions
assert.deepStrictEqual(espree.VisitorKeys.Program, ["body"]);
assert.deepStrictEqual(espree.VisitorKeys.VariableDeclaration, ["declarations"]);
assert.deepStrictEqual(espree.VisitorKeys.VariableDeclarator, ["id", "init"]);
assert.deepStrictEqual(espree.VisitorKeys.FunctionDeclaration, ["id", "params", "body"]);
assert.deepStrictEqual(espree.VisitorKeys.BinaryExpression, ["left", "right"]);
assert.deepStrictEqual(espree.VisitorKeys.CallExpression, ["callee", "arguments"]);
assert.deepStrictEqual(espree.VisitorKeys.BlockStatement, ["body"]);
assert.deepStrictEqual(espree.VisitorKeys.ReturnStatement, ["argument"]);

// 4. Verify AST traversal using espree.VisitorKeys
const code = "const x = 10; function add(y) { return x + y; } add(5);";
const ast = espree.parse(code, { ecmaVersion: "latest" });

assert.strictEqual(ast.type, "Program");

const visitedTypes = [];
function walk(node) {
  if (!node || typeof node !== "object") return;
  if (node.type) {
    visitedTypes.push(node.type);
    const keys = espree.VisitorKeys[node.type] || [];
    for (const key of keys) {
      const child = node[key];
      if (Array.isArray(child)) {
        for (const item of child) {
          walk(item);
        }
      } else if (child && typeof child === "object") {
        walk(child);
      }
    }
  }
}

walk(ast);

const expectedTypes = [
  "Program",
  "VariableDeclaration",
  "VariableDeclarator",
  "Identifier",
  "Literal",
  "FunctionDeclaration",
  "BlockStatement",
  "ReturnStatement",
  "BinaryExpression",
  "CallExpression"
];

for (const type of expectedTypes) {
  assert(visitedTypes.includes(type), `Expected visited AST types to include ${type}`);
}

// 5. Verify handling when node type is unknown or has empty visitor keys
assert.strictEqual(espree.VisitorKeys.UnknownNodeType, undefined);
const fallbackKeys = espree.VisitorKeys.UnknownNodeType || [];
assert.deepStrictEqual(fallbackKeys, []);

console.log("espree.VisitorKeys contract passed");