err-code 2.0.3: err-code

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/err-code@2.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/err-code@2.0.3
Demonstrate these symbols/APIs:
  - err-code

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:sha256:3ca9d486ba3c7ec13f3c015b087c356df038fe61a2e3b2b11a238a01da74456b","contract":["errCode attaches a string error code to an Error instance under the code property","errCode attaches additional custom properties to an Error instance alongside the error code","errCode accepts an object of custom properties as the second argument when code is omitted","errCode throws TypeError when the first argument is not an Error instance"],"goal":"verify pkg:npm/err-code@2.0.3","kind":"HOW","packages":["pkg:npm/err-code@2.0.3"],"schemaVersion":1,"symbols":["err-code"]},"contractCommand":["node","test/contract.cjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/err-code@2.0.3"],"schemaVersion":1,"subject":"pkg:npm/err-code@2.0.3","symbols":["err-code"],"verifierAdapter":"node-typescript@1"}

'use strict';

const errCode = require('err-code');

function createCodedError(message, code, properties) {
  const error = new Error(message);
  return errCode(error, code, properties);
}

module.exports = {
  createCodedError,
  errCode
};

{
  "name": "sample-err-code",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-err-code",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "err-code": "2.0.3"
      }
    },
    "node_modules/err-code": {
      "version": "2.0.3",
      "resolved": "https://registry.npmjs.org/err-code/-/err-code-2.0.3.tgz",
      "integrity": "sha512-2bmlRpNKBxT/CRmPOlyISQpNj+qSeYvcym/uT0Jx2bMOlKLtSy1ZmLuVxSEKKyor/N5yhvp/ZiG1oE3DEYMSFA==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-err-code",
  "version": "1.0.0",
  "private": true,
  "description": "verify pkg:npm/err-code@2.0.3",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.cjs"
  },
  "dependencies": {
    "err-code": "2.0.3"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/err-code@2.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:npm/err-code@2.0.3"
  ],
  "symbols": [
    "err-code"
  ]
}

'use strict';

const assert = require('assert');
const errCode = require('err-code');
const { createCodedError } = require('../index.js');

// 1. errCode attaches a string error code to an Error instance under the code property
const err1 = new Error('File not found');
const res1 = errCode(err1, 'ENOENT');
assert.strictEqual(res1, err1, 'Must return the same Error instance');
assert.strictEqual(res1.code, 'ENOENT', 'Error code must be set');
assert.strictEqual(res1.message, 'File not found', 'Error message must be preserved');

// 2. errCode attaches additional custom properties to an Error instance alongside the error code
const err2 = new Error('Permission denied');
const res2 = errCode(err2, 'EACCES', { targetFile: 'config.json', retryable: false });
assert.strictEqual(res2.code, 'EACCES', 'Error code must be set');
assert.strictEqual(res2.targetFile, 'config.json', 'Custom property targetFile must be attached');
assert.strictEqual(res2.retryable, false, 'Custom property retryable must be attached');

// 3. errCode accepts an object of custom properties as the second argument when code is omitted
const err3 = new Error('Database connection failed');
const res3 = errCode(err3, { code: 'ECONNREFUSED', host: 'localhost', port: 5432 });
assert.strictEqual(res3.code, 'ECONNREFUSED', 'Code from properties object must be set');
assert.strictEqual(res3.host, 'localhost', 'Host property must be attached');
assert.strictEqual(res3.port, 5432, 'Port property must be attached');

// 4. Helper function createCodedError
const helperErr = createCodedError('Resource busy', 'EBUSY', { attempts: 3 });
assert(helperErr instanceof Error, 'Result must be an Error instance');
assert.strictEqual(helperErr.code, 'EBUSY', 'Code must be EBUSY');
assert.strictEqual(helperErr.attempts, 3, 'Attempts must be 3');

// 5. errCode throws TypeError when the first argument is not an Error instance
assert.throws(() => {
  errCode('Invalid error string', 'EINVAL');
}, (err) => {
  return err instanceof TypeError && /Please pass an Error to err-code/.test(err.message);
}, 'Must throw TypeError if first argument is not an Error');

console.log('Contract tests passed successfully.');
process.exit(0);