follow-redirects 1.16.0

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/follow-redirects@1.16.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/follow-redirects@1.16.0
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - 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:sha256:24396618ab3d586916cac766910334e6fb925c5e4bd0b91e19f846f0b9efbe34","constraints":{"executionContext":"node"},"contract":["followRedirects exports http and https drop-in wrappers and wrap function","http.get follows 301 and 302 redirects automatically to destination URL and populates responseUrl","trackRedirects option records redirect history array with status codes and URLs for each hop","maxRedirects option limits maximum redirect count and emits error when limit is exceeded","beforeRedirect callback allows intercepting and inspecting redirect options before following"],"goal":"verify pkg:npm/follow-redirects@1.16.0","kind":"HOW","packages":["pkg:npm/follow-redirects@1.16.0"],"schemaVersion":1},"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","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/follow-redirects@1.16.0"],"schemaVersion":1,"subject":"pkg:npm/follow-redirects@1.16.0","verifierAdapter":"node-typescript@1"}

{
  "name": "sample-follow-redirects",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-follow-redirects",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "follow-redirects": "1.16.0"
      }
    },
    "node_modules/follow-redirects": {
      "version": "1.16.0",
      "resolved": "https://registry.npmjs.org/follow-redirects/-/follow-redirects-1.16.0.tgz",
      "integrity": "sha512-y5rN/uOsadFT/JfYwhxRS5R7Qce+g3zG97+JrtFZlC9klX/W5hD7iiLzScI4nZqUS7DNUdhPgw4xI8W2LuXlUw==",
      "license": "MIT",
      "engines": {
        "node": ">=4.0"
      },
      "peerDependenciesMeta": {
        "debug": {
          "optional": true
        }
      }
    }
  }
}

{
  "name": "sample-follow-redirects",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "follow-redirects": "1.16.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/follow-redirects@1.16.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/follow-redirects@1.16.0"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert/strict';
import http from 'node:http';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const followRedirects = require('follow-redirects');
const { http: fHttp, https: fHttps } = followRedirects;

// 1. followRedirects exports http and https drop-in wrappers and wrap function
assert.equal(typeof fHttp, 'object', 'followRedirects.http should be an object');
assert.equal(typeof fHttp.get, 'function', 'followRedirects.http.get should be a function');
assert.equal(typeof fHttp.request, 'function', 'followRedirects.http.request should be a function');
assert.equal(typeof fHttps, 'object', 'followRedirects.https should be an object');
assert.equal(typeof fHttps.get, 'function', 'followRedirects.https.get should be a function');
assert.equal(typeof fHttps.request, 'function', 'followRedirects.https.request should be a function');
assert.equal(typeof followRedirects.wrap, 'function', 'followRedirects.wrap should be a function');

// Create local test HTTP server for offline testing
const server = http.createServer((req, res) => {
  if (req.url === '/redirect-1') {
    res.writeHead(302, { Location: '/redirect-2' });
    res.end();
  } else if (req.url === '/redirect-2') {
    res.writeHead(301, { Location: '/final' });
    res.end();
  } else if (req.url === '/final') {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('final destination reached');
  } else if (req.url === '/loop-a') {
    res.writeHead(302, { Location: '/loop-b' });
    res.end();
  } else if (req.url === '/loop-b') {
    res.writeHead(302, { Location: '/loop-a' });
    res.end();
  } else {
    res.writeHead(404);
    res.end('not found');
  }
});

await new Promise((resolve) => server.listen(0, '127.0.0.1', resolve));
const port = server.address().port;
const baseUrl = `http://127.0.0.1:${port}`;

try {
  // 2. http.get follows 301 and 302 redirects automatically to destination URL and populates responseUrl
  await new Promise((resolve, reject) => {
    fHttp.get(`${baseUrl}/redirect-1`, (res) => {
      let data = '';
      res.on('data', (chunk) => { data += chunk; });
      res.on('end', () => {
        try {
          assert.equal(res.statusCode, 200);
          assert.equal(data, 'final destination reached');
          assert.equal(res.responseUrl, `${baseUrl}/final`);
          resolve();
        } catch (e) {
          reject(e);
        }
      });
    }).on('error', reject);
  });

  // 3. trackRedirects option records redirect history array with status codes and URLs for each hop
  await new Promise((resolve, reject) => {
    fHttp.get({
      host: '127.0.0.1',
      port,
      path: '/redirect-1',
      trackRedirects: true,
    }, (res) => {
      let data = '';
      res.on('data', (chunk) => { data += chunk; });
      res.on('end', () => {
        try {
          assert.equal(res.statusCode, 200);
          assert.ok(Array.isArray(res.redirects), 'res.redirects should be an array');
          assert.equal(res.redirects.length, 3);
          assert.equal(res.redirects[0].statusCode, 302);
          assert.equal(res.redirects[0].url, `${baseUrl}/redirect-1`);
          assert.equal(res.redirects[1].statusCode, 301);
          assert.equal(res.redirects[1].url, `${baseUrl}/redirect-2`);
          assert.equal(res.redirects[2].statusCode, 200);
          assert.equal(res.redirects[2].url, `${baseUrl}/final`);
          resolve();
        } catch (e) {
          reject(e);
        }
      });
    }).on('error', reject);
  });

  // 4. maxRedirects option limits maximum redirect count and emits error when limit is exceeded
  await new Promise((resolve, reject) => {
    const req = fHttp.get({
      host: '127.0.0.1',
      port,
      path: '/loop-a',
      maxRedirects: 3,
    });
    req.on('error', (err) => {
      try {
        assert.match(err.message, /Maximum number of redirects exceeded/i);
        resolve();
      } catch (e) {
        reject(e);
      }
    });
    req.on('response', () => {
      reject(new Error('Expected maxRedirects error but received response'));
    });
  });

  // 5. beforeRedirect callback allows intercepting and inspecting redirect options before following
  const redirectedHops = [];
  await new Promise((resolve, reject) => {
    fHttp.get({
      host: '127.0.0.1',
      port,
      path: '/redirect-1',
      beforeRedirect: (options, responseDetails) => {
        redirectedHops.push({
          path: options.path,
          statusCode: responseDetails.statusCode,
        });
      },
    }, (res) => {
      res.resume();
      res.on('end', () => {
        try {
          assert.equal(redirectedHops.length, 2);
          assert.equal(redirectedHops[0].statusCode, 302);
          assert.equal(redirectedHops[0].path, '/redirect-2');
          assert.equal(redirectedHops[1].statusCode, 301);
          assert.equal(redirectedHops[1].path, '/final');
          resolve();
        } catch (e) {
          reject(e);
        }
      });
    }).on('error', reject);
  });

  console.log('All contract assertions passed.');
} finally {
  await new Promise((resolve) => server.close(resolve));
}