estraverse 5.3.0: replace

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 estraverse.replace in pkg:npm/estraverse@5.3.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/estraverse@5.3.0
Demonstrate these symbols/APIs:
  - estraverse.replace
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:sha256:7cc829a2c12eca35bd0fd985d3b13f16691ee8241a955e0e5b8802192e6066f7","constraints":{"executionContext":"node"},"contract":["replace substitutes matching AST node with new node returned from enter callback","replace substitutes matching AST node with new node returned from leave callback","replace removes node from AST array when VisitorOption.Remove is returned from enter","replace removes node from AST array when VisitorOption.Remove is returned from leave","replace skips descending into children of replaced node when VisitorOption.Skip is returned","replace aborts full traversal immediately when VisitorOption.Break is returned","replace passes current node and parent node to enter and leave callbacks","replace transforms nested AST expressions and returns updated root AST structure"],"goal":"verify estraverse.replace in pkg:npm/estraverse@5.3.0","kind":"HOW","packages":["pkg:npm/estraverse@5.3.0"],"schemaVersion":1,"symbols":["estraverse.replace"]},"contractCommand":["node","test/contract.mjs"],"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/estraverse@5.3.0"],"schemaVersion":1,"subject":"pkg:npm/estraverse@5.3.0","symbols":["estraverse.replace"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-estraverse-replace",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-estraverse-replace",
      "version": "1.0.0",
      "dependencies": {
        "estraverse": "5.3.0"
      }
    },
    "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": "sample-estraverse-replace",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "estraverse": "5.3.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify estraverse.replace in pkg:npm/estraverse@5.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/estraverse@5.3.0"
  ],
  "symbols": [
    "estraverse.replace"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert/strict';
import estraverse from 'estraverse';

// 1. replace substitutes matching AST node with new node returned from enter callback
{
  const ast = {
    type: 'Program',
    body: [
      {
        type: 'ExpressionStatement',
        expression: {
          type: 'Identifier',
          name: 'foo'
        }
      }
    ]
  };

  const result = estraverse.replace(ast, {
    enter(node) {
      if (node.type === 'Identifier' && node.name === 'foo') {
        return { type: 'Identifier', name: 'bar' };
      }
    }
  });

  assert.equal(result.body[0].expression.name, 'bar');
  assert.equal(ast.body[0].expression.name, 'bar');
}

// 2. replace substitutes matching AST node with new node returned from leave callback
{
  const ast = {
    type: 'Program',
    body: [
      {
        type: 'ExpressionStatement',
        expression: {
          type: 'Literal',
          value: 42,
          raw: '42'
        }
      }
    ]
  };

  const result = estraverse.replace(ast, {
    leave(node) {
      if (node.type === 'Literal' && node.value === 42) {
        return { type: 'Literal', value: 100, raw: '100' };
      }
    }
  });

  assert.equal(result.body[0].expression.value, 100);
}

// 3. replace removes node from AST array when VisitorOption.Remove is returned from enter
{
  const ast = {
    type: 'Program',
    body: [
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'keep1' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'removeMe' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'keep2' } }
    ]
  };

  estraverse.replace(ast, {
    enter(node) {
      if (node.type === 'ExpressionStatement' && node.expression.name === 'removeMe') {
        return estraverse.VisitorOption.Remove;
      }
    }
  });

  assert.equal(ast.body.length, 2);
  assert.equal(ast.body[0].expression.name, 'keep1');
  assert.equal(ast.body[1].expression.name, 'keep2');
}

// 4. replace removes node from AST array when VisitorOption.Remove is returned from leave
{
  const ast = {
    type: 'Program',
    body: [
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'first' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'drop' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'second' } }
    ]
  };

  estraverse.replace(ast, {
    leave(node) {
      if (node.type === 'ExpressionStatement' && node.expression.name === 'drop') {
        return estraverse.VisitorOption.Remove;
      }
    }
  });

  assert.equal(ast.body.length, 2);
  assert.equal(ast.body[0].expression.name, 'first');
  assert.equal(ast.body[1].expression.name, 'second');
}

// 5. replace skips descending into children of replaced node when VisitorOption.Skip is returned
{
  const ast = {
    type: 'Program',
    body: [
      {
        type: 'BinaryExpression',
        operator: '+',
        left: { type: 'Identifier', name: 'a' },
        right: { type: 'Identifier', name: 'b' }
      }
    ]
  };

  const visitedTypes = [];
  estraverse.replace(ast, {
    enter(node) {
      visitedTypes.push(node.type);
      if (node.type === 'BinaryExpression') {
        return estraverse.VisitorOption.Skip;
      }
    }
  });

  assert.deepEqual(visitedTypes, ['Program', 'BinaryExpression']);
}

// 6. replace aborts full traversal immediately when VisitorOption.Break is returned
{
  const ast = {
    type: 'Program',
    body: [
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'one' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'stop' } },
      { type: 'ExpressionStatement', expression: { type: 'Identifier', name: 'three' } }
    ]
  };

  const visitedNames = [];
  estraverse.replace(ast, {
    enter(node) {
      if (node.type === 'Identifier') {
        visitedNames.push(node.name);
        if (node.name === 'stop') {
          return estraverse.VisitorOption.Break;
        }
      }
    }
  });

  assert.deepEqual(visitedNames, ['one', 'stop']);
}

// 7. replace passes current node and parent node to enter and leave callbacks
{
  const ast = {
    type: 'Program',
    body: [
      {
        type: 'ExpressionStatement',
        expression: {
          type: 'Identifier',
          name: 'target'
        }
      }
    ]
  };

  let enterParentType = null;
  let leaveParentType = null;

  estraverse.replace(ast, {
    enter(node, parent) {
      if (node.type === 'Identifier' && node.name === 'target') {
        enterParentType = parent ? parent.type : null;
      }
    },
    leave(node, parent) {
      if (node.type === 'Identifier' && node.name === 'target') {
        leaveParentType = parent ? parent.type : null;
      }
    }
  });

  assert.equal(enterParentType, 'ExpressionStatement');
  assert.equal(leaveParentType, 'ExpressionStatement');
}

// 8. replace transforms nested AST expressions and returns updated root AST structure
{
  const ast = {
    type: 'Program',
    body: [
      {
        type: 'ExpressionStatement',
        expression: {
          type: 'BinaryExpression',
          operator: '+',
          left: {
            type: 'BinaryExpression',
            operator: '*',
            left: { type: 'Literal', value: 2, raw: '2' },
            right: { type: 'Literal', value: 3, raw: '3' }
          },
          right: { type: 'Literal', value: 4, raw: '4' }
        }
      }
    ]
  };

  const result = estraverse.replace(ast, {
    leave(node) {
      if (
        node.type === 'BinaryExpression' &&
        node.operator === '*' &&
        node.left.type === 'Literal' &&
        node.right.type === 'Literal'
      ) {
        const val = node.left.value * node.right.value;
        return {
          type: 'Literal',
          value: val,
          raw: String(val)
        };
      }
    }
  });

  assert.equal(result.type, 'Program');
  const expr = result.body[0].expression;
  assert.equal(expr.type, 'BinaryExpression');
  assert.equal(expr.operator, '+');
  assert.equal(expr.left.type, 'Literal');
  assert.equal(expr.left.value, 6);
  assert.equal(expr.right.value, 4);
}