error-ex 1.3.4

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/error-ex@1.3.4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/error-ex@1.3.4

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:sha256:42dabfce4ae6e58ec0d6e2f02e690f3dcb25b2acc975f9852e10ba7ec0af35f4","contract":["errorEx creates a custom Error subclass that can be instantiated with or without new","errorEx unwraps message when instantiated with an existing Error instance","errorEx defaults error name to Error when name parameter is omitted or not a string","errorEx.append modifier appends formatted property values to error message","errorEx.line modifier inserts custom formatted line into error stack trace","errorEx instances support message setter and stack setter override"],"goal":"verify pkg:npm/error-ex@1.3.4","kind":"HOW","packages":["pkg:npm/error-ex@1.3.4"],"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/error-ex@1.3.4"],"schemaVersion":1,"subject":"pkg:npm/error-ex@1.3.4","verifierAdapter":"node-typescript@1"}

{
  "name": "sample-error-ex",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-error-ex",
      "version": "1.0.0",
      "dependencies": {
        "error-ex": "1.3.4"
      }
    },
    "node_modules/error-ex": {
      "version": "1.3.4",
      "resolved": "https://registry.npmjs.org/error-ex/-/error-ex-1.3.4.tgz",
      "integrity": "sha512-sqQamAnR14VgCr1A618A3sGrygcpK+HEbenA/HiEAkkUwcZIIB/tgWqHFxWgOyDh4nB4JCRimh79dR5Ywc9MDQ==",
      "license": "MIT",
      "dependencies": {
        "is-arrayish": "^0.2.1"
      }
    },
    "node_modules/is-arrayish": {
      "version": "0.2.1",
      "resolved": "https://registry.npmjs.org/is-arrayish/-/is-arrayish-0.2.1.tgz",
      "integrity": "sha512-zz06S8t0ozoDXMG+ube26zeCTNXcKIPJZJi8hBrF4idCLms4CG9QtK7qBl1boi5ODzFpjswb5JPmHCbMpjaYzg==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-error-ex",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "error-ex": "1.3.4"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/error-ex@1.3.4",
  "kind": "HOW",
  "packages": [
    "pkg:npm/error-ex@1.3.4"
  ]
}

import assert from 'node:assert/strict';
import errorEx from 'error-ex';

// 1. errorEx creates a custom Error subclass that can be instantiated with or without new
{
  const CustomError = errorEx('CustomError');
  const errWithNew = new CustomError('something failed');
  const errWithoutNew = CustomError('call without new');

  assert.ok(errWithNew instanceof Error);
  assert.ok(errWithNew instanceof CustomError);
  assert.equal(errWithNew.name, 'CustomError');
  assert.equal(errWithNew.message, 'something failed');
  assert.ok(errWithNew.stack.includes('CustomError: something failed'));

  assert.ok(errWithoutNew instanceof Error);
  assert.ok(errWithoutNew instanceof CustomError);
  assert.equal(errWithoutNew.name, 'CustomError');
  assert.equal(errWithoutNew.message, 'call without new');
}

// 2. errorEx unwraps message when instantiated with an existing Error instance
{
  const CustomError = errorEx('CustomError');
  const original = new Error('original message');
  const wrapped = new CustomError(original);

  assert.equal(wrapped.message, 'original message');
  assert.ok(wrapped instanceof CustomError);
  assert.ok(wrapped instanceof Error);
}

// 3. errorEx defaults error name to Error when name parameter is omitted or not a string
{
  const DefaultError = errorEx();
  const err = new DefaultError('default name test');

  assert.equal(err.name, 'Error');
  assert.equal(err.message, 'default name test');
  assert.ok(err instanceof Error);
}

// 4. errorEx.append modifier appends formatted property values to error message
{
  const JSONError = errorEx('JSONError', {
    fileName: errorEx.append('in %s'),
  });

  const err = new JSONError('Unexpected token');
  assert.equal(err.message, 'Unexpected token');

  err.fileName = 'package.json';
  assert.equal(err.message, 'Unexpected token in package.json');
}

// 5. errorEx.line modifier inserts custom formatted line into error stack trace
{
  const FileError = errorEx('FileError', {
    location: errorEx.line('at %s'),
  });

  const err = new FileError('read error');
  err.location = 'line 42, column 5';

  const stack = err.stack;
  const stackLines = stack.split('\n');
  assert.equal(stackLines[0], 'FileError: read error');
  assert.equal(stackLines[1], '    at line 42, column 5');
}

// 6. errorEx instances support message setter and stack setter override
{
  const CustomError = errorEx('CustomError');
  const err = new CustomError('initial message');

  err.message = 'updated message';
  assert.equal(err.message, 'updated message');

  err.stack = 'CustomError: manual stack\n    at test';
  assert.equal(err.stack, 'CustomError: manual stack\n    at test');
}