esrecurse 4.3.0: Visitor, visit

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/esrecurse@4.3.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/esrecurse@4.3.0
Demonstrate these symbols/APIs:
  - esrecurse.Visitor
  - esrecurse.visit

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:sha256:6b941a805a4849effae08c1dc97a0d398ab99302eeeb14a701c35078779659fd","contract":["assert esrecurse.version is 4.3.0","assert esrecurse.visit traverses AST nodes and invokes visitor callbacks matching node types","assert esrecurse.Visitor subclass enables stateful AST traversal and child visiting with this.visitChildren","assert esrecurse.visit supports childVisitorKeys option for custom AST node types","assert esrecurse.visit supports fallback option iteration for unknown node types","assert esrecurse.visit safely handles null and undefined nodes without throwing"],"goal":"verify pkg:npm/esrecurse@4.3.0","kind":"HOW","packages":["pkg:npm/esrecurse@4.3.0"],"schemaVersion":1,"symbols":["esrecurse.Visitor","esrecurse.visit"]},"contractCommand":["node","test/contract.js"],"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/esrecurse@4.3.0"],"schemaVersion":1,"subject":"pkg:npm/esrecurse@4.3.0","symbols":["esrecurse.Visitor","esrecurse.visit"],"verifierAdapter":"node-typescript@1"}

{
  "name": "csx-sample-esrecurse",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "csx-sample-esrecurse",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "esrecurse": "4.3.0"
      }
    },
    "node_modules/esrecurse": {
      "version": "4.3.0",
      "resolved": "https://registry.npmjs.org/esrecurse/-/esrecurse-4.3.0.tgz",
      "integrity": "sha512-KmfKL3b6G+RXvP8N1vr3Tq1kL/oCFgn2NYXEtqP8/L3pKapUA4G8cFVaoF3SU323CD4XypR/ffioHmkti6/Tag==",
      "license": "BSD-2-Clause",
      "dependencies": {
        "estraverse": "^5.2.0"
      },
      "engines": {
        "node": ">=4.0"
      }
    },
    "node_modules/estraverse": {
      "version": "5.3.0",
      "resolved": "https://registry.npmjs.org/estraverse/-/estraverse-5.3.0.tgz",
      "integrity": "sha512-MMdARuVEQziNTeJD8DgMqmhwR11BRQ/cBP+pLtYdSTnf3MIO8fFeiINEbX36ZdNlfU/7A9f3gUw49B3oQsvwBA==",
      "license": "BSD-2-Clause",
      "engines": {
        "node": ">=4.0"
      }
    }
  }
}

{
  "name": "csx-sample-esrecurse",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for esrecurse",
  "main": "test/contract.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "esrecurse": "4.3.0"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/esrecurse@4.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/esrecurse@4.3.0"
  ],
  "symbols": [
    "esrecurse.Visitor",
    "esrecurse.visit"
  ]
}

const assert = require('node:assert/strict');
const esrecurse = require('esrecurse');

// 1. Version property
assert.strictEqual(typeof esrecurse.version, 'string');
assert.strictEqual(esrecurse.version, '4.3.0');

// 2. esrecurse.visit traverses AST nodes and calls visitor handlers matching node type
const ast = {
  type: 'Program',
  body: [
    {
      type: 'VariableDeclaration',
      kind: 'const',
      declarations: [
        {
          type: 'VariableDeclarator',
          id: { type: 'Identifier', name: 'answer' },
          init: { type: 'Literal', value: 42 }
        }
      ]
    },
    {
      type: 'FunctionDeclaration',
      id: { type: 'Identifier', name: 'compute' },
      params: [{ type: 'Identifier', name: 'input' }],
      body: {
        type: 'BlockStatement',
        body: [
          {
            type: 'ReturnStatement',
            argument: {
              type: 'BinaryExpression',
              operator: '+',
              left: { type: 'Identifier', name: 'input' },
              right: { type: 'Identifier', name: 'answer' }
            }
          }
        ]
      }
    }
  ]
};

const visitedIdentifiers = [];
esrecurse.visit(ast, {
  Identifier(node) {
    visitedIdentifiers.push(node.name);
  }
});
assert.deepStrictEqual(visitedIdentifiers, ['answer', 'compute', 'input', 'input', 'answer']);

// 3. Visitor class extension with visitChildren
class LiteralCollector extends esrecurse.Visitor {
  constructor() {
    super();
    this.literals = [];
  }
  Literal(node) {
    this.literals.push(node.value);
  }
}

const collector = new LiteralCollector();
collector.visit(ast);
assert.deepStrictEqual(collector.literals, [42]);

// 4. Custom childVisitorKeys for custom AST nodes
const customAst = {
  type: 'CustomModule',
  customChildren: [
    { type: 'Identifier', name: 'customA' },
    { type: 'Identifier', name: 'customB' }
  ]
};
const customNames = [];
esrecurse.visit(
  customAst,
  {
    Identifier(node) {
      customNames.push(node.name);
    }
  },
  {
    childVisitorKeys: {
      CustomModule: ['customChildren']
    }
  }
);
assert.deepStrictEqual(customNames, ['customA', 'customB']);

// 5. Fallback iteration for unknown node types
const arbitraryAst = {
  type: 'UnknownWrapper',
  item: { type: 'Identifier', name: 'wrappedVar' }
};
const fallbackNames = [];
esrecurse.visit(
  arbitraryAst,
  {
    Identifier(node) {
      fallbackNames.push(node.name);
    }
  },
  { fallback: 'iteration' }
);
assert.deepStrictEqual(fallbackNames, ['wrappedVar']);

// 6. Safe handling of null and undefined nodes
assert.doesNotThrow(() => {
  esrecurse.visit(null, {});
  esrecurse.visit(undefined, {});
});

console.log('All esrecurse contract assertions passed.');