@typescript-eslint/typescript-estree 8.66.0: simpleTraverse

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 @typescript-eslint/typescript-estree.simpleTraverse in pkg:npm/%40typescript-eslint/typescript-estree@8.66.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40typescript-eslint/typescript-estree@8.66.0
Demonstrate these symbols/APIs:
  - @typescript-eslint/typescript-estree.simpleTraverse
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.

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{
  "name": "verify-typescript-estree-simple-traverse",
  "version": "1.0.0",
  "private": true,
  "description": "verify @typescript-eslint/typescript-estree.simpleTraverse in pkg:npm/@typescript-eslint/typescript-estree@8.66.0",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.cjs"
  },
  "dependencies": {
    "@typescript-eslint/typescript-estree": "8.66.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @typescript-eslint/typescript-estree.simpleTraverse in pkg:npm/%40typescript-eslint/typescript-estree@8.66.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40typescript-eslint/typescript-estree@8.66.0"
  ],
  "symbols": [
    "@typescript-eslint/typescript-estree.simpleTraverse"
  ],
  "constraints": {
    "executionContext": "node"
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  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const { simpleTraverse } = require('@typescript-eslint/typescript-estree');

/**
 * Traverses an AST and collects all visited node types.
 *
 * @param {import('@typescript-eslint/typescript-estree').TSESTree.Node} ast
 * @returns {string[]}
 */
function collectNodeTypes(ast) {
  const types = [];
  simpleTraverse(ast, {
    enter(node) {
      types.push(node.type);
    },
  });
  return types;
}

/**
 * Traverses an AST using node-specific visitors to collect identifier names.
 *
 * @param {import('@typescript-eslint/typescript-estree').TSESTree.Node} ast
 * @returns {string[]}
 */
function collectIdentifiers(ast) {
  const identifiers = [];
  simpleTraverse(ast, {
    visitors: {
      Identifier(node) {
        identifiers.push(node.name);
      },
    },
  });
  return identifiers;
}

/**
 * Traverses an AST and attaches parent pointers to each child node.
 *
 * @param {import('@typescript-eslint/typescript-estree').TSESTree.Node} ast
 * @returns {import('@typescript-eslint/typescript-estree').TSESTree.Node}
 */
function attachParents(ast) {
  simpleTraverse(ast, { enter() {} }, true);
  return ast;
}

module.exports = {
  collectNodeTypes,
  collectIdentifiers,
  attachParents,
};

const assert = require('assert');
const { parse, simpleTraverse } = require('@typescript-eslint/typescript-estree');
const {
  collectNodeTypes,
  collectIdentifiers,
  attachParents,
} = require('../src/index.js');

// 1. simpleTraverse visits AST nodes using an enter callback
const varCode = 'const count: number = 42;';
const varAst = parse(varCode);
const visitedNodes = [];

simpleTraverse(varAst, {
  enter(node, parent) {
    visitedNodes.push({
      type: node.type,
      parentType: parent ? parent.type : null,
    });
  },
});

assert(visitedNodes.length > 0, 'Should visit at least one node');
assert.strictEqual(visitedNodes[0].type, 'Program');
assert.strictEqual(visitedNodes[0].parentType, null);
assert.strictEqual(visitedNodes[1].type, 'VariableDeclaration');
assert.strictEqual(visitedNodes[1].parentType, 'Program');
assert(
  visitedNodes.some((node) => node.type === 'TSNumberKeyword'),
  'Should visit TSNumberKeyword node'
);

const helperTypes = collectNodeTypes(varAst);
assert.deepStrictEqual(
  helperTypes,
  visitedNodes.map((n) => n.type)
);

// 2. simpleTraverse dispatches to specific node type visitor callbacks
const fnCode = 'function add(a: number, b: number): number { const sum = a + b; return sum; }';
const fnAst = parse(fnCode);
const visitedIdentifiers = [];
const visitedBinaryOps = [];

simpleTraverse(fnAst, {
  visitors: {
    Identifier(node, parent) {
      visitedIdentifiers.push(node.name);
      assert(parent !== undefined, 'Parent should be provided to visitor');
    },
    BinaryExpression(node) {
      visitedBinaryOps.push(node.operator);
    },
  },
});

assert.deepStrictEqual(visitedIdentifiers, ['add', 'a', 'b', 'sum', 'a', 'b', 'sum']);
assert.deepStrictEqual(visitedBinaryOps, ['+']);

const helperIdentifiers = collectIdentifiers(fnAst);
assert.deepStrictEqual(helperIdentifiers, visitedIdentifiers);

// 3. simpleTraverse sets parent pointers on child AST nodes when enabled
const exprCode = 'const greeting: string = "hello world";';
const exprAst = parse(exprCode);

assert.strictEqual(exprAst.body[0].parent, undefined);

attachParents(exprAst);

const declaration = exprAst.body[0];
const declarator = declaration.declarations[0];
const identifier = declarator.id;

assert.strictEqual(declaration.parent, exprAst);
assert.strictEqual(declarator.parent, declaration);
assert.strictEqual(identifier.parent, declarator);

// 4. simpleTraverse accepts custom visitorKeys to control AST node traversal
const customAst = parse('const flag: boolean = true;');
const visitedWithCustomKeys = [];

simpleTraverse(customAst, {
  visitorKeys: {
    Program: [],
  },
  enter(node) {
    visitedWithCustomKeys.push(node.type);
  },
});

assert.deepStrictEqual(visitedWithCustomKeys, ['Program']);

console.log('Contract verification passed successfully.');