CodeSampleX

Sample

@babel/plugin-transform-class-properties 8.0.1: transformClassProperties

Verified sample for npm @babel/plugin-transform-class-properties 8.0.1: transformClassProperties. The contract ran on node 22 · linux debian/x64 · docker and…

sha256:7eac71b81a1cbfbde8009c425e77fcf4748d6e14770c2cf7bf51dd725e800d62

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 node 22.23 linux 24 · ubuntu · glibc 2.39 x64 node 22.23 javascript npm 10

Verification-run environments

Environment Contract Stages Run
node 22 · linux debian/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22@sha256:8a34c4ab3ea2…		 2026-09-02

Case

HOW
Goal
verify transformClassProperties in pkg:npm/%40babel/plugin-transform-class-properties@8.0.1
Packages
Symbols
  • transformClassProperties
Environment
node 22.23.2
Created
2026-09-02T08:05:17Z

Contract

  1. transforms instance class fields using _defineProperty in constructor under standard mode
  2. transforms static class fields using _defineProperty on constructor under standard mode
  3. transforms instance and static class fields to direct assignment under loose mode
  4. transforms computed and Symbol property keys on class declarations
  5. evaluates transformed classes preserving runtime instance and static property semantics

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.mjs
  • 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 transformClassProperties in pkg:npm/%40babel/plugin-transform-class-properties@8.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40babel/plugin-transform-class-properties@8.0.1
Demonstrate these symbols/APIs:
  - transformClassProperties
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.
csx.json
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package-lock.json
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package.json
{
  "name": "sample-babel-transform-class-properties",
  "version": "1.0.0",
  "type": "module",
  "dependencies": {
    "@babel/core": "8.0.1",
    "@babel/plugin-transform-class-properties": "8.0.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify transformClassProperties in pkg:npm/%40babel/plugin-transform-class-properties@8.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40babel/plugin-transform-class-properties@8.0.1"
  ],
  "symbols": [
    "transformClassProperties"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}
src/index.mjs
import { transformSync } from '@babel/core';
import transformClassPropertiesPlugin from '@babel/plugin-transform-class-properties';

const plugin = transformClassPropertiesPlugin.default || transformClassPropertiesPlugin;

/**
 * Transforms class properties in JavaScript code using @babel/plugin-transform-class-properties.
 *
 * @param {string} code - Source code containing class property definitions.
 * @param {object} [options={}] - Transformation options.
 * @param {boolean} [options.loose=false] - Whether to transform properties in loose mode.
 * @returns {string} The transformed JavaScript code.
 */
export function compileClassProperties(code, options = {}) {
  const pluginConfig = options.loose !== undefined
    ? [plugin, { loose: options.loose }]
    : [plugin];

  const result = transformSync(code, {
    plugins: [pluginConfig],
    configFile: false,
    babelrc: false,
  });

  return result?.code ?? '';
}

export default plugin;
test/contract.mjs
import assert from 'node:assert';
import plugin, { compileClassProperties } from '../src/index.mjs';

// 1. transforms instance class fields using _defineProperty in constructor under standard mode
{
  const source = `
class Counter {
  count = 0;
  increment = () => {
    this.count += 1;
  };
}
`;
  const output = compileClassProperties(source);
  assert.strictEqual(output.includes('_defineProperty(this, "count", 0)'), true);
  assert.strictEqual(output.includes('_defineProperty(this, "increment"'), true);
}

// 2. transforms static class fields using _defineProperty on constructor under standard mode
{
  const source = `
class AppConfig {
  static version = '2.0.0';
  static maxRetries = 3;
}
`;
  const output = compileClassProperties(source);
  assert.strictEqual(output.includes('_defineProperty(AppConfig, "version", "2.0.0")') || output.includes("_defineProperty(AppConfig, \"version\", '2.0.0')"), true);
  assert.strictEqual(output.includes('_defineProperty(AppConfig, "maxRetries", 3)'), true);
}

// 3. transforms instance and static class fields to direct assignment under loose mode
{
  const source = `
class User {
  name = 'Anonymous';
  static role = 'guest';
}
`;
  const output = compileClassProperties(source, { loose: true });
  assert.strictEqual(output.includes('_defineProperty'), false);
  assert.strictEqual(output.includes("this.name = 'Anonymous'"), true);
  assert.strictEqual(output.includes("User.role = 'guest'"), true);
}

// 4. transforms computed and Symbol property keys on class declarations
{
  const source = `
const symId = Symbol('id');
class Entity {
  [symId] = 'E-100';
  static ['category'] = 'general';
}
`;
  const output = compileClassProperties(source);
  assert.strictEqual(output.includes('_defineProperty(this, symId, "E-100")') || output.includes("_defineProperty(this, symId, 'E-100')"), true);
  assert.strictEqual(output.includes('_defineProperty(Entity, "category", "general")') || output.includes("_defineProperty(Entity, 'category', 'general')") || output.includes("_defineProperty(Entity, \"category\", 'general')"), true);
}

// 5. evaluates transformed classes preserving runtime instance and static property semantics
{
  const source = `
class MathService {
  multiplier = 2;
  static defaultBase = 10;

  calculate(val) {
    return (val + MathService.defaultBase) * this.multiplier;
  }
}
`;
  const output = compileClassProperties(source);
  const factory = new Function(output + '\nreturn MathService;');
  const MathService = factory();

  assert.strictEqual(MathService.defaultBase, 10);
  const service = new MathService();
  assert.strictEqual(service.multiplier, 2);
  assert.strictEqual(service.calculate(5), 30);
}

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

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