fs.mkdtempDisposableSync() / fsPromises.mkdtempDisposable() throw and leak the directory when the path is a Buffer

[gengjiawen]

Version

v27.0.0-nightly20261007aa1bf2cc37 (main at 6d5e309)

Platform

Linux x64

Subsystem

fs

What steps will reproduce the bug?

const fs = require('node:fs');
const os = require('node:os');
const path = require('node:path');

const base = fs.mkdtempSync(path.join(os.tmpdir(), 'repro-'));
const prefix = path.join(base, 'x-');

for (const args of [[Buffer.from(prefix)], [prefix, { encoding: 'buffer' }]]) {
  try {
    fs.mkdtempDisposableSync(...args);
  } catch (err) {
    console.log(err.message);
    console.log('left behind:', fs.readdirSync(base));
  }
}

fs.promises.mkdtempDisposable() behaves the same way.

How often does it reproduce? Is there a required condition?

Always, whenever the created path is a Buffer: the prefix is a Buffer, or encoding is 'buffer'.

What is the expected behavior? Why is that the expected behavior?

Both calls return the disposable object with a Buffer path, and remove() deletes the directory. The docs list path as {string|Buffer}, and since #64397 a Buffer prefix defaults encoding to 'buffer'.

What do you see instead?

The "paths[1]" argument must be of type string. Received an instance of Buffer
left behind: [ 'x-Kx8KEG' ]
The "paths[1]" argument must be of type string. Received an instance of Buffer
left behind: [ 'x-Kx8KEG', 'x-gV98fq' ]

The ERR_INVALID_ARG_TYPE is thrown after the directory has been created. The caller never gets the disposable object, so nothing removes the directory.

Additional information

After binding.mkdtemp() creates the directory, both functions stash its absolute path for remove() with pathModule.resolve(cwd, path), and path.resolve() only accepts strings. The { encoding: 'buffer' } form has failed this way since mkdtempDisposable() was added in #58516; #64397 made every Buffer prefix take the same path.

I have a fix and will open a PR.