vary 1.1.2

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/vary@1.1.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/vary@1.1.2

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:sha256:916edf5792a7a04cfd078ccd24ec0006e491cd746316bca53dfda326fc37a8b1","contract":["vary(res, field) sets the Vary header on response object","vary(res, field) appends field to existing Vary header without duplicating","vary(res, field) accepts an array of header field names","vary(res, field) sets Vary header to * when field is *","vary.append(header, field) returns updated header string without modifying existing headers","vary.append(header, field) returns * if header or field contains *","vary.append(header, field) throws TypeError when header or field argument is invalid","vary(res, field) throws TypeError when res argument is invalid or missing methods"],"goal":"verify pkg:npm/vary@1.1.2","kind":"HOW","packages":["pkg:npm/vary@1.1.2"],"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/vary@1.1.2"],"schemaVersion":1,"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-vary",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-vary",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "vary": "1.1.2"
      }
    },
    "node_modules/vary": {
      "version": "1.1.2",
      "resolved": "https://registry.npmjs.org/vary/-/vary-1.1.2.tgz",
      "integrity": "sha512-BNGbWLfd0eUPabhkXUVm0j8uuvREyTh5ovRa/dyow/BqAbZJyC+5fU+IzQOzmAKzYqYRAISoRhdQr3eIZ/PXqg==",
      "license": "MIT",
      "engines": {
        "node": ">= 0.8"
      }
    }
  }
}

{
  "name": "sample-vary",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "vary": "1.1.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/vary@1.1.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/vary@1.1.2"
  ]
}

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

const require = createRequire(import.meta.url);
const vary = require('vary');

// 1. Module export verification
assert.equal(typeof vary, 'function', 'vary must be a function');
assert.equal(typeof vary.append, 'function', 'vary.append must be a function');

// Helper to create mock response object
function createMockRes(initialHeaders = {}) {
  const headers = { ...initialHeaders };
  return {
    headers,
    getHeader(name) {
      return this.headers[name.toLowerCase()] || this.headers[name];
    },
    setHeader(name, value) {
      this.headers[name.toLowerCase()] = value;
    }
  };
}

// 2. vary(res, field) sets the Vary header on response object
const res1 = createMockRes();
vary(res1, 'Accept-Encoding');
assert.equal(res1.getHeader('Vary'), 'Accept-Encoding');

// 3. vary(res, field) appends field to existing Vary header without duplicating
const res2 = createMockRes({ vary: 'Accept' });
vary(res2, 'Accept-Encoding');
assert.equal(res2.getHeader('Vary'), 'Accept, Accept-Encoding');

// Case-insensitive duplicate check should not re-add
vary(res2, 'accept-encoding');
assert.equal(res2.getHeader('Vary'), 'Accept, Accept-Encoding');

// 4. vary(res, field) accepts an array of header field names
const res3 = createMockRes();
vary(res3, ['Accept', 'User-Agent', 'Origin']);
assert.equal(res3.getHeader('Vary'), 'Accept, User-Agent, Origin');

// 5. vary(res, field) sets Vary header to * when field is *
const res4 = createMockRes({ vary: 'Accept, Accept-Language' });
vary(res4, '*');
assert.equal(res4.getHeader('Vary'), '*');

// 6. vary.append(header, field) returns updated header string without modifying existing headers
const header1 = 'Accept-Encoding';
const appended1 = vary.append(header1, 'Origin');
assert.equal(appended1, 'Accept-Encoding, Origin');
assert.equal(header1, 'Accept-Encoding'); // unchanged original string

const appendedArray = vary.append('Accept', ['Accept-Language', 'User-Agent']);
assert.equal(appendedArray, 'Accept, Accept-Language, User-Agent');

// 7. vary.append(header, field) returns * if header or field contains *
assert.equal(vary.append('*', 'Accept'), '*');
assert.equal(vary.append('Accept', '*'), '*');
assert.equal(vary.append('Accept', ['Accept-Encoding', '*']), '*');

// 8. vary.append(header, field) throws TypeError when header or field argument is invalid
assert.throws(
  () => vary.append(null, 'Accept'),
  (err) => err instanceof TypeError && err.message === 'header argument is required'
);
assert.throws(
  () => vary.append('Accept', null),
  (err) => err instanceof TypeError && err.message === 'field argument is required'
);
assert.throws(
  () => vary.append('Accept', 'invalid header with space'),
  (err) => err instanceof TypeError && err.message === 'field argument contains an invalid header name'
);

// 9. vary(res, field) throws TypeError when res argument is invalid or missing methods
assert.throws(
  () => vary(null, 'Accept'),
  (err) => err instanceof TypeError && err.message === 'res argument is required'
);
assert.throws(
  () => vary({}, 'Accept'),
  (err) => err instanceof TypeError && err.message === 'res argument is required'
);
assert.throws(
  () => vary({ getHeader: () => {} }, 'Accept'),
  (err) => err instanceof TypeError && err.message === 'res argument is required'
);

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