CodeSampleX

Sample

express 5.2.1

Verified sample for npm express 5.2.1. The contract ran on node 22 · linux alpine/x64 · docker and passed: express() creates an application instance and…

sha256:9ab8b3fc8e0562fee4c6b35848021c4df71d8b332ee57bc250caa38421deb44c

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		 2026-08-20

Case

HOW
Goal
verify pkg:npm/express@5.2.1
Packages
Created
2026-08-20T13:48:38Z

Contract

  1. express() creates an application instance and express.Router() creates modular route handlers
  2. nested router with mergeParams: true inherits and resolves parent path parameters across route hierarchies
  3. res.set() configures custom response headers, res.cookie() sets HttpOnly and SameSite cookie options, and res.status().json() delivers formatted JSON responses
  4. async route handlers returning rejected promises automatically propagate errors to Express error-handling middleware without unhandled rejections

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.js
  • 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/express@5.2.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/express@5.2.1

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-express",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of express",
  "main": "src/index.js",
  "license": "MIT-0",
  "dependencies": {
    "express": "5.2.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/express@5.2.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/express@5.2.1"
  ]
}
src/index.js
const express = require('express');

/**
 * Creates and configures an Express application with async error handling,
 * nested router parameter merging, and standard response helpers.
 * @returns {import('express').Express}
 */
function createApp() {
  const app = express();

  // JSON parsing middleware
  app.use(express.json());

  // Nested router with mergeParams
  const parentRouter = express.Router();
  const childRouter = express.Router({ mergeParams: true });

  childRouter.get('/items/:itemId', (req, res) => {
    res.status(200).json({
      orgId: req.params.orgId,
      itemId: req.params.itemId
    });
  });

  parentRouter.use('/orgs/:orgId', childRouter);
  app.use('/api', parentRouter);

  // Response header and cookie demonstration
  app.get('/api/response-helpers', (req, res) => {
    res.set('X-Custom-Header', 'express-v5');
    res.cookie('auth_token', 'test-token-12345', {
      httpOnly: true,
      sameSite: 'strict',
      path: '/'
    });
    res.status(200).json({ success: true, message: 'Response helpers verified' });
  });

  // Async route handler that throws - testing native Express 5 Promise rejection handling
  app.get('/api/async-error', async (req, res) => {
    throw new Error('Async execution failed');
  });

  // Error-handling middleware
  app.use((err, req, res, next) => {
    res.status(500).json({
      error: true,
      message: err.message
    });
  });

  return app;
}

module.exports = {
  createApp,
  express
};
test/contract.mjs
import assert from 'node:assert';
import http from 'node:http';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const { createApp, express } = require('../src/index.js');

// 1. Verify exports and types
assert.strictEqual(typeof express, 'function', 'express must be exported as a function');
assert.strictEqual(typeof express.Router, 'function', 'express.Router must be a function');
assert.strictEqual(typeof createApp, 'function', 'createApp must be a function');

const app = createApp();
assert.ok(app, 'app must be created');
assert.strictEqual(typeof app.listen, 'function', 'app.listen must be a function');

const server = http.createServer(app);

async function runContract() {
  await new Promise((resolve, reject) => {
    server.listen(0, '127.0.0.1', () => {
      resolve();
    });
    server.on('error', reject);
  });

  const address = server.address();
  const baseUrl = `http://127.0.0.1:${address.port}`;

  try {
    // 1. Verify nested router with mergeParams: true propagates parent route parameters
    const nestedRes = await fetch(`${baseUrl}/api/orgs/org-42/items/item-99`);
    assert.strictEqual(nestedRes.status, 200, 'Nested router should return 200');
    const nestedData = await nestedRes.json();
    assert.deepStrictEqual(nestedData, { orgId: 'org-42', itemId: 'item-99' }, 'Parent and child params should match');

    // 2. Verify response helpers (res.set, res.cookie, res.status, res.json)
    const helperRes = await fetch(`${baseUrl}/api/response-helpers`);
    assert.strictEqual(helperRes.status, 200, 'Response helpers should return 200');
    assert.strictEqual(helperRes.headers.get('x-custom-header'), 'express-v5', 'Custom header should match');
    const cookieHeader = helperRes.headers.get('set-cookie');
    assert.ok(cookieHeader && cookieHeader.includes('auth_token=test-token-12345'), 'Cookie header should contain auth_token');
    assert.ok(cookieHeader.toLowerCase().includes('httponly'), 'Cookie should be HttpOnly');
    assert.ok(cookieHeader.toLowerCase().includes('samesite=strict'), 'Cookie should have SameSite=Strict');
    const helperData = await helperRes.json();
    assert.deepStrictEqual(helperData, { success: true, message: 'Response helpers verified' });

    // 3. Verify Express 5 native async route handler rejection propagation to error middleware
    const asyncErrRes = await fetch(`${baseUrl}/api/async-error`);
    assert.strictEqual(asyncErrRes.status, 500, 'Async rejected error should be caught by error middleware with 500');
    const asyncErrData = await asyncErrRes.json();
    assert.deepStrictEqual(asyncErrData, { error: true, message: 'Async execution failed' }, 'Error middleware payload should match');

    console.log('Contract tests passed successfully.');
  } finally {
    await new Promise((resolve) => server.close(resolve));
  }
}

runContract().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
});

Origin Seeder

anonymous