common-ancestor-path 1.0.1

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/common-ancestor-path@1.0.1
Kind: HOW

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

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:ef21d3213ac2ef99d0c2306c973356335615db1e5a817da0ec6aa3920f98865b","contract":["commonAncestorPath('alpha/beta/gamma', 'alpha/beta/delta', 'alpha/beta/epsilon/zeta') returns 'alpha/beta'","commonAncestorPath('alpha/beta/gamma', 'alpha/beta/gamma') returns 'alpha/beta/gamma'","commonAncestorPath('alpha/beta/gamma/../delta', 'alpha/beta/epsilon') normalizes segments and returns 'alpha/beta'","commonAncestorPath('alpha/beta', 'gamma/delta') returns '' when relative paths share no leading segment","commonAncestorPath('/alpha/beta', 'alpha/beta') returns null when paths have different roots"],"goal":"verify pkg:npm/common-ancestor-path@1.0.1","kind":"HOW","packages":["pkg:npm/common-ancestor-path@1.0.1"],"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/common-ancestor-path@1.0.1"],"schemaVersion":1,"subject":"pkg:npm/common-ancestor-path@1.0.1","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,
  "type": "module",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "common-ancestor-path": "1.0.1"
  }
}

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

import assert from 'node:assert/strict';
import commonAncestorPath from 'common-ancestor-path';

// 1. Common ancestor of multiple nested relative paths
assert.equal(
  commonAncestorPath('alpha/beta/gamma', 'alpha/beta/delta', 'alpha/beta/epsilon/zeta'),
  'alpha/beta'
);

// 2. Identical paths return the path itself
assert.equal(
  commonAncestorPath('alpha/beta/gamma', 'alpha/beta/gamma'),
  'alpha/beta/gamma'
);

// 3. Non-normalized paths with .. segments are normalized before comparison
assert.equal(
  commonAncestorPath('alpha/beta/gamma/../delta', 'alpha/beta/epsilon'),
  'alpha/beta'
);

// 4. Relative paths without shared leading segment yield empty string
assert.equal(
  commonAncestorPath('alpha/beta', 'gamma/delta'),
  ''
);

// 5. Absolute vs relative paths have different roots and return null
assert.equal(
  commonAncestorPath('/alpha/beta', 'alpha/beta'),
  null
);