CodeSampleX

Sample

@babel/plugin-transform-classes 7.29.7

Verified sample for npm @babel/plugin-transform-classes 7.29.7. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:d52da89710c9932815754be4ba8894c21bcf07e28d31f43f72caed958e0d96e3

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment linux 24 · ubuntu · glibc 2.39 x64 npm

Verification-run environments

Environment Contract Stages Run
node 22 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-21

Case

HOW
Goal
verify pkg:npm/%40babel/plugin-transform-classes@7.29.7
Packages
Created
2026-08-21T06:44:05Z

Contract

  1. transforms ES6 class declarations and method definitions into ES5 constructor functions with prototype methods
  2. enforces runtime constructor call checks to throw TypeError when a class is invoked without new
  3. transforms class inheritance with extends, super calls, and prototype chain wiring
  4. transforms static methods and getter/setter property descriptors

Files

  • PROMPT.md
  • csx.json
  • index.mjs
  • package-lock.json
  • package.json
  • spec.json
  • test/contract.mjs

Download the source artifact (tar.gz)

Source

PROMPT.md
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/%40babel/plugin-transform-classes@7.29.7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40babel/plugin-transform-classes@7.29.7

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.
csx.json
{"case":{"caseId":"case:sha256:b03af7303d7cace517aee04320c4b191225e080eb9b636e80aa6f1b53723f96e","contract":["transforms ES6 class declarations and method definitions into ES5 constructor functions with prototype methods","enforces runtime constructor call checks to throw TypeError when a class is invoked without new","transforms class inheritance with extends, super calls, and prototype chain wiring","transforms static methods and getter/setter property descriptors"],"goal":"verify pkg:npm/%40babel/plugin-transform-classes@7.29.7","kind":"HOW","packages":["pkg:npm/%40babel/plugin-transform-classes@7.29.7"],"schemaVersion":1},"contractCommand":["node","test/contract.mjs"],"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/%40babel/plugin-transform-classes@7.29.7"],"schemaVersion":1,"subject":"pkg:npm/%40babel/plugin-transform-classes@7.29.7","verifierAdapter":"node-typescript@1"}
index.mjs
import * as babel from '@babel/core';
import transformClassesPlugin from '@babel/plugin-transform-classes';

/**
 * Transforms JavaScript code containing ES6 classes to ES5 using @babel/plugin-transform-classes.
 * @param {string} sourceCode - The input JavaScript code containing classes.
 * @param {object} [pluginOptions] - Optional configuration for @babel/plugin-transform-classes.
 * @returns {string} The transformed ES5 code.
 */
export function transformClasses(sourceCode, pluginOptions = {}) {
  const result = babel.transformSync(sourceCode, {
    configFile: false,
    babelrc: false,
    plugins: [
      [transformClassesPlugin, pluginOptions]
    ]
  });
  return result?.code ?? '';
}
package-lock.json
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package.json
{
  "name": "sample-babel-transform-classes",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "@babel/core": "7.29.7",
    "@babel/plugin-transform-classes": "7.29.7"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/%40babel/plugin-transform-classes@7.29.7",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40babel/plugin-transform-classes@7.29.7"
  ]
}
test/contract.mjs
import assert from 'node:assert';
import { transformClasses } from '../index.mjs';

console.log('Running contract tests for @babel/plugin-transform-classes...');

// Test 1: Basic class transformation and prototype methods
{
  const inputCode = `
    class Greeter {
      constructor(name) {
        this.name = name;
      }
      greet() {
        return "Hello, " + this.name + "!";
      }
    }
  `;

  const outputCode = transformClasses(inputCode);

  assert.ok(outputCode, 'Transformation result should not be empty');
  assert.ok(!outputCode.includes('class Greeter'), 'Output should not contain class Greeter');

  // Evaluate the transformed code in a safe scope
  const fn = new Function(outputCode + '; return Greeter;');
  const Greeter = fn();

  const instance = new Greeter('World');
  assert.strictEqual(instance.name, 'World');
  assert.strictEqual(instance.greet(), 'Hello, World!');

  // Calling class constructor without 'new' must throw TypeError
  assert.throws(
    () => { Greeter('World'); },
    {
      name: 'TypeError',
      message: /Cannot call a class as a function/
    },
    'Calling class constructor without new must throw TypeError'
  );
  console.log('✔ Test 1 passed: Basic class transformation, method dispatch, and constructor call check');
}

// Test 2: Class inheritance with extends and super
{
  const inputCode = `
    class Shape {
      constructor(type) {
        this.type = type;
      }
      describe() {
        return "Shape: " + this.type;
      }
    }
    class Circle extends Shape {
      constructor(radius) {
        super("Circle");
        this.radius = radius;
      }
      area() {
        return Math.PI * this.radius * this.radius;
      }
    }
  `;

  const outputCode = transformClasses(inputCode);
  assert.ok(!outputCode.includes('class Shape'), 'Output should not contain class Shape');
  assert.ok(!outputCode.includes('class Circle'), 'Output should not contain class Circle');

  const fn = new Function(outputCode + '; return { Shape, Circle };');
  const { Shape, Circle } = fn();

  const circle = new Circle(5);
  assert.strictEqual(circle.type, 'Circle');
  assert.strictEqual(circle.radius, 5);
  assert.strictEqual(circle.describe(), 'Shape: Circle');
  assert.strictEqual(circle.area(), Math.PI * 25);
  assert.ok(circle instanceof Shape, 'Circle instance should be an instance of Shape');
  assert.ok(circle instanceof Circle, 'Circle instance should be an instance of Circle');
  console.log('✔ Test 2 passed: Class inheritance with extends, super constructor, and instanceof');
}

// Test 3: Static methods and properties / getters / setters
{
  const inputCode = `
    class Temperature {
      constructor(celsius) {
        this._celsius = celsius;
      }
      get fahrenheit() {
        return this._celsius * 1.8 + 32;
      }
      set fahrenheit(value) {
        this._celsius = (value - 32) / 1.8;
      }
      static fromFahrenheit(f) {
        return new Temperature((f - 32) / 1.8);
      }
    }
  `;

  const outputCode = transformClasses(inputCode);
  const fn = new Function(outputCode + '; return Temperature;');
  const Temperature = fn();

  const t = new Temperature(0);
  assert.strictEqual(t.fahrenheit, 32);
  t.fahrenheit = 212;
  assert.strictEqual(Math.round(t._celsius), 100);

  const t2 = Temperature.fromFahrenheit(68);
  assert.strictEqual(Math.round(t2._celsius), 20);
  console.log('✔ Test 3 passed: Static methods, getters, and setters transformation');
}

console.log('All contract tests passed successfully.');

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