fs.realpath 1.0.0: fs.realpath

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 fs.realpath in pkg:npm/fs.realpath@1.0.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/fs.realpath@1.0.0
Demonstrate these symbols/APIs:
  - fs.realpath
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:abb7746e6f62c510c497d15e3976bb2299474f4c3a5b4f0106a2e503072d0869","constraints":{"executionContext":"node"},"contract":["Resolving a canonical file path with realpathSync returns the resolved absolute path","Resolving a symlink with realpathSync resolves the symlink target path","Resolving a symlink asynchronously with realpath passes the resolved path to the callback","Resolving a non-existent path with realpathSync throws an ENOENT error","Resolving a non-existent path with realpath passes an ENOENT error to the callback","Calling monkeypatch replaces fs.realpath and fs.realpathSync with package implementations, and unmonkeypatch restores them"],"goal":"verify fs.realpath in pkg:npm/fs.realpath@1.0.0","kind":"HOW","packages":["pkg:npm/fs.realpath@1.0.0"],"schemaVersion":1,"symbols":["fs.realpath"]},"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/fs.realpath@1.0.0"],"schemaVersion":1,"subject":"pkg:npm/fs.realpath@1.0.0","symbols":["fs.realpath"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-fs-realpath",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-fs-realpath",
      "version": "1.0.0",
      "dependencies": {
        "fs.realpath": "1.0.0"
      }
    },
    "node_modules/fs.realpath": {
      "version": "1.0.0",
      "resolved": "https://registry.npmjs.org/fs.realpath/-/fs.realpath-1.0.0.tgz",
      "integrity": "sha512-OO0pH2lK6a0hZnAdau5ItzHPI6pUlvI7jMVnxUQRtw4owF2wk8lOSabtGDCTP4Ggrg2MbGnWO9X8K1t4+fGMDw==",
      "license": "ISC"
    }
  }
}

{
  "name": "sample-fs-realpath",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "fs.realpath": "1.0.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify fs.realpath in pkg:npm/fs.realpath@1.0.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/fs.realpath@1.0.0"
  ],
  "symbols": [
    "fs.realpath"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import realpathPkg from 'fs.realpath';

const { realpath, realpathSync, sync, monkeypatch, unmonkeypatch } = realpathPkg;

const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'csx-fs-realpath-'));

try {
	const targetFile = path.join(tmpDir, 'target.txt');
	fs.writeFileSync(targetFile, 'content');
	const linkFile = path.join(tmpDir, 'link.txt');
	fs.symlinkSync(targetFile, linkFile);

	// 1. Resolving a canonical file path with realpathSync returns the resolved absolute path
	{
		const resolved = realpathSync(targetFile);
		assert.equal(typeof resolved, 'string');
		assert.equal(resolved, fs.realpathSync(targetFile));
		// Also verify alias sync()
		assert.equal(sync(targetFile), resolved);
	}

	// 2. Resolving a symlink with realpathSync resolves the symlink target path
	{
		const resolvedLink = realpathSync(linkFile);
		const resolvedTarget = realpathSync(targetFile);
		assert.equal(resolvedLink, resolvedTarget);
	}

	// 3. Resolving a symlink asynchronously with realpath passes the resolved path to the callback
	{
		await new Promise((resolve, reject) => {
			realpath(linkFile, (err, res) => {
				if (err) return reject(err);
				try {
					assert.equal(res, realpathSync(targetFile));
					resolve();
				} catch (e) {
					reject(e);
				}
			});
		});
	}

	// 4. Resolving a non-existent path with realpathSync throws an ENOENT error
	{
		const nonExistent = path.join(tmpDir, 'does-not-exist.txt');
		assert.throws(
			() => {
				realpathSync(nonExistent);
			},
			(err) => {
				return err && err.code === 'ENOENT';
			}
		);
	}

	// 5. Resolving a non-existent path with realpath passes an ENOENT error to the callback
	{
		const nonExistent = path.join(tmpDir, 'does-not-exist-async.txt');
		await new Promise((resolve, reject) => {
			realpath(nonExistent, (err, res) => {
				try {
					assert.ok(err, 'Expected error for non-existent path');
					assert.equal(err.code, 'ENOENT');
					assert.equal(res, undefined);
					resolve();
				} catch (e) {
					reject(e);
				}
			});
		});
	}

	// 6. Calling monkeypatch replaces fs.realpath and fs.realpathSync with package implementations, and unmonkeypatch restores them
	{
		const origFsRealpath = fs.realpath;
		const origFsRealpathSync = fs.realpathSync;

		monkeypatch();
		assert.equal(fs.realpath, realpath);
		assert.equal(fs.realpathSync, realpathSync);

		unmonkeypatch();
		assert.equal(fs.realpath, origFsRealpath);
		assert.equal(fs.realpathSync, origFsRealpathSync);
	}
} finally {
	fs.rmSync(tmpDir, { recursive: true, force: true });
}