common-ancestor-path 1.0.1: commonAncestorPath

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 commonAncestorPath in pkg:npm/common-ancestor-path@1.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/common-ancestor-path@1.0.1
Demonstrate these symbols/APIs:
  - commonAncestorPath

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:e1aa22dfabda0e9655b9a186ee2ea116d94c34135a71dd78a817e49982314bf0","contract":["commonAncestorPath(a, b) returns the identical path when both arguments are equal","commonAncestorPath(a, b) returns the deepest shared ancestor path for two paths sharing leading segments","commonAncestorPath(...paths) reduces across three or more paths to return their shared ancestor","commonAncestorPath(a, b) normalizes dot-dot segments before comparing distinct paths","commonAncestorPath(a, b) returns an empty string when relative paths share no leading segment","commonAncestorPath(a, b) returns null when paths have different parsed roots","commonAncestorPath() throws TypeError when called with no arguments"],"goal":"verify commonAncestorPath in pkg:npm/common-ancestor-path@1.0.1","kind":"HOW","packages":["pkg:npm/common-ancestor-path@1.0.1"],"schemaVersion":1,"symbols":["commonAncestorPath"]},"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/common-ancestor-path@1.0.1"],"schemaVersion":1,"subject":"pkg:npm/common-ancestor-path@1.0.1","symbols":["commonAncestorPath"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-common-ancestor-path",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-common-ancestor-path",
      "version": "1.0.0",
      "dependencies": {
        "common-ancestor-path": "1.0.1"
      }
    },
    "node_modules/common-ancestor-path": {
      "version": "1.0.1",
      "resolved": "https://registry.npmjs.org/common-ancestor-path/-/common-ancestor-path-1.0.1.tgz",
      "integrity": "sha512-L3sHRo1pXXEqX8VU28kfgUY+YGsk09hPqZiZmLacNib6XNTCM8ubYeT7ryXQw8asB1sKgcU5lkB7ONug08aB8w==",
      "license": "ISC"
    }
  }
}

{
  "name": "sample-common-ancestor-path",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for commonAncestorPath in common-ancestor-path",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.cjs"
  },
  "dependencies": {
    "common-ancestor-path": "1.0.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify commonAncestorPath in pkg:npm/common-ancestor-path@1.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/common-ancestor-path@1.0.1"
  ],
  "symbols": [
    "commonAncestorPath"
  ]
}

const commonAncestorPath = require('common-ancestor-path');

/**
 * Find the common ancestor of two or more paths.
 * @param {...string} paths - Input file or directory paths
 * @returns {string | null} The common ancestor path, or null if roots differ
 */
function findCommonAncestor(...paths) {
  return commonAncestorPath(...paths);
}

module.exports = {
  commonAncestorPath,
  findCommonAncestor
};

const assert = require('node:assert');
const path = require('node:path');
const commonAncestorPath = require('common-ancestor-path');
const { findCommonAncestor } = require('../src/index.js');

const j = (...parts) => parts.join(path.sep);

// 1. commonAncestorPath(a, b) returns the identical path when both arguments are equal
assert.strictEqual(
  commonAncestorPath(j('alpha', 'beta', 'gamma'), j('alpha', 'beta', 'gamma')),
  j('alpha', 'beta', 'gamma')
);

// 2. commonAncestorPath(a, b) returns the deepest shared ancestor path for two paths sharing leading segments
assert.strictEqual(
  commonAncestorPath(j('alpha', 'beta', 'gamma'), j('alpha', 'beta', 'delta')),
  j('alpha', 'beta')
);
assert.strictEqual(
  findCommonAncestor(j('alpha', 'beta', 'gamma'), j('alpha', 'beta', 'delta')),
  j('alpha', 'beta')
);

// 3. commonAncestorPath(...paths) reduces across three or more paths to return their shared ancestor
assert.strictEqual(
  commonAncestorPath(
    j('alpha', 'beta', 'gamma', 'one'),
    j('alpha', 'beta', 'gamma', 'two'),
    j('alpha', 'beta', 'other')
  ),
  j('alpha', 'beta')
);

// 4. commonAncestorPath(a, b) normalizes dot-dot segments before comparing distinct paths
assert.strictEqual(
  commonAncestorPath(
    j('alpha', 'beta', 'gamma', '..', 'delta'),
    j('alpha', 'beta', 'epsilon')
  ),
  j('alpha', 'beta')
);

// 5. commonAncestorPath(a, b) returns an empty string when relative paths share no leading segment
assert.strictEqual(
  commonAncestorPath(j('alpha', 'beta'), j('gamma', 'delta')),
  ''
);

// 6. commonAncestorPath(a, b) returns null when paths have different parsed roots
const rootedPath = path.sep + j('alpha', 'beta');
const relativePath = j('alpha', 'beta');
assert.strictEqual(commonAncestorPath(rootedPath, relativePath), null);

// 7. commonAncestorPath() throws TypeError when called with no arguments
assert.throws(() => {
  commonAncestorPath();
}, TypeError);

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