stackback 0.0.2

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/stackback@0.0.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/stackback@0.0.2

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:sha256:53ba639d9347aa4a0a40b25cc3e71757e272280933a589a1a53863bbbe85ce3b","contract":["assert stackback returns an array of V8 CallSite objects from an unformatted error","assert CallSite objects provide standard getFileName, getLineNumber, and getFunctionName methods","assert error stack string formatting is preserved after capturing CallSites","assert repeated calls on the same error return cached CallSites","assert stackback returns an empty array when error stack was already accessed beforehand"],"goal":"verify pkg:npm/stackback@0.0.2","kind":"HOW","packages":["pkg:npm/stackback@0.0.2"],"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","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/stackback@0.0.2"],"schemaVersion":1,"subject":"pkg:npm/stackback@0.0.2","verifierAdapter":"node-typescript@1"}

const stackback = require('stackback');

/**
 * Capture CallSite objects from an error instance using stackback.
 *
 * @param {Error} err - Error instance whose stack trace to capture.
 * @returns {Array<object>} Array of V8 CallSite objects.
 */
function getCallSites(err) {
  return stackback(err);
}

module.exports = {
  getCallSites,
  stackback,
};

{
  "name": "sample-stackback-verify",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-stackback-verify",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "stackback": "0.0.2"
      }
    },
    "node_modules/stackback": {
      "version": "0.0.2",
      "resolved": "https://registry.npmjs.org/stackback/-/stackback-0.0.2.tgz",
      "integrity": "sha512-1XMJE5fQo1jGH6Y/7ebnwPOBEkIEnT4QF32d5R1+VXdXveM0IBMJt8zfaxX1P3QhVwrYe+576+jkANtSS2mBbw==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-stackback-verify",
  "version": "1.0.0",
  "description": "Clean-room sample verifying pkg:npm/stackback@0.0.2",
  "main": "index.js",
  "license": "MIT-0",
  "dependencies": {
    "stackback": "0.0.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/stackback@0.0.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/stackback@0.0.2"
  ]
}

import assert from 'node:assert';
import stackback from 'stackback';
import { getCallSites } from '../index.js';

// 1. Returns an array of V8 CallSite objects for a newly created Error
function sampleFunction() {
  return new Error('test error');
}

const err1 = sampleFunction();
const callsites = getCallSites(err1);

assert(Array.isArray(callsites), 'stackback must return an array');
assert(callsites.length > 0, 'stackback must return at least one CallSite');

// 2. CallSite objects have standard V8 methods
const topFrame = callsites[0];
assert.strictEqual(typeof topFrame.getFileName, 'function', 'CallSite must have getFileName method');
assert.strictEqual(typeof topFrame.getLineNumber, 'function', 'CallSite must have getLineNumber method');
assert.strictEqual(typeof topFrame.getColumnNumber, 'function', 'CallSite must have getColumnNumber method');
assert.strictEqual(typeof topFrame.getFunctionName, 'function', 'CallSite must have getFunctionName method');

assert.strictEqual(topFrame.getFunctionName(), 'sampleFunction', 'Top CallSite function name must match caller function');
assert.strictEqual(typeof topFrame.getLineNumber(), 'number', 'Line number must be a number');

// 3. Error stack property remains a string and formatting is preserved
assert.strictEqual(typeof err1.stack, 'string', 'Error.stack must be a string');
assert(err1.stack.includes('test error'), 'Error.stack must contain error message');

// 4. Repeated calls on the same error return cached CallSites
const repeatedCallsites = stackback(err1);
assert.strictEqual(repeatedCallsites, callsites, 'Repeated stackback calls on same error must return cached callsites');

// 5. If error stack was already accessed prior to stackback capture, returns empty array
const err2 = new Error('already formatted');
const formattedStack = err2.stack;
assert.strictEqual(typeof formattedStack, 'string');
const emptyCallsites = stackback(err2);
assert(Array.isArray(emptyCallsites) && emptyCallsites.length === 0, 'stackback must return empty array if stack was accessed beforehand');

console.log('All contract assertions passed.');