`fs.existsSync` mock incorrectly throws `ENOTDIR` when the real `fs.existsSync` returns false

[vlukashov]

It looks like the fs.existsSync mock added in #387 is in some cases inconsistent with the actual fs.existsSync behaviour.

Example (index.js file):

import { default as mock } from "mock-fs";
import * as fs from "node:fs";
import * as path from "node:path";
import { fileURLToPath } from "node:url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

try {
  console.log(`native fs.existsSync('index.js/path'):`);
  console.log(`>`, fs.existsSync("index.js/path"));
  console.log();

  mock({ "index.js": mock.load(`${__dirname}/index.js`) });
  console.log(`mocked fs.existsSync('index.js/path'):`);
  console.log(`>`, fs.existsSync("index.js/path"));
  mock.restore();
} catch (e) {
  console.error(e);
}

Expected output

native fs.existsSync('index.js/path'):
> false

mocked fs.existsSync('index.js/path'):
> false

Actual output

native fs.existsSync('index.js/path'):
> false

mocked fs.existsSync('index.js/path'):
Error: ENOTDIR, not a directory 'index.js/path'
    at FileSystem.getItem (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/filesystem.js:128:15)
    at Binding.<anonymous> (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/binding.js:1488:31)
    at maybeCallback (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/binding.js:85:17)
    at Binding.exists (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/binding.js:1486:10)
    at Binding.existsSync (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/binding.js:1507:15)
    at Object.<anonymous> (/Users/viktor/code/sandbox/mock-fs-exists-sync-issue/node_modules/mock-fs/lib/index.js:39:39)
    at Module.existsSync (node:fs:292:18)
    at file:///Users/viktor/code/sandbox/mock-fs-exists-sync-issue/index.js:16:23
    at ModuleJob.run (node:internal/modules/esm/module_job:222:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:316:24) {
  code: 'ENOTDIR',
  errno: -20,
  path: 'index.js/path'
}

[vlukashov]

I come across a library (oclif) that uses fs.existsSync in such way in its internals. This issue makes using the latest versions of mock-fs with code using that library impossible.

Workaround: use an older version of mock-fs (pre-#387, e.g. 5.2.0) and an older version of NodeJS (e.g. 18).

[tschaub]

Thanks for the report. This should be addressed in mock-fs@5.4.1.

[vlukashov]

Awesome to see such a quick fix! 🎉
I'm looking forward to trying it out. 5.4.1 is not on npm yet, but I'll give it a try as soon as it appears there.

[tschaub]

5.4.1 is not on npm yet

Oops. That was an oversight. You should find it there now.