Discrepancy between `fs.rmSync` and `fs/promises.rm` behavior with `.` and `..` in paths

Version

v25.6.1

Platform

Darwin moxy.lan 25.3.0 Darwin Kernel Version 25.3.0: Wed Jan 28 20:47:03 PST 2026; root:xnu-12377.81.4~5/RELEASE_ARM64_T6031 arm64

Subsystem

lib/internal/fs/rimraf.js

What steps will reproduce the bug?

Create a nested folder:

mkdir -p a/b/c/d

Attempt to delete with this weirdly constructed path:

Welcome to Node.js v25.6.1.
Type ".help" for more information.
> await require('fs/promises').rm('a/b/../.', { recursive: true, force: true })
Uncaught [Error: EINVAL: invalid argument, rmdir 'a/b/../.'] {
  errno: -22,
  code: 'EINVAL',
  syscall: 'rmdir',
  path: 'a/b/../.'
}

Verify that nothing was removed:

$ tree
./
└── a/
    └── b/
        └── c/
            └── d/

Attempt to delete synchronously:

> require('fs').rmSync('a/b/../.', { recursive: true, force: true })
undefined

It was (mostly?) removed:

$ tree
./
└── a/

The weird thing is that a/b/../. should resolve to just a, so it's weird that it only deletes up to b. It's almost as if the rmSync method is coalescing /../. into just /.

Also, if the . is not the last item, then it seems to be fine? a/b/.././b deletes the b folder, and a/b/.. deletes just b, but not a.

At least, it seems like the sync and asynchronous methods should either both fail, or both succeed, with the same error.

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

every time, see repro steps above

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

sync and asynchronous rm methods should fail and succeed in the same way on the same input.

What do you see instead?

Some cases where rmSync succeeds, and fs/promises.rm fails.

Additional information

I have a fix that I could land in the upstream rimraf library, and I'd of course be happy to send a PR to node to bring it back into alignment, since there have also been some improvements in performance and Windows reliability.

But it'd be good to know what the intended behavior is, so that the errors can be made consistent with Node's intended design first.

Start with lib/internal/fs/rimraf.js and run the reported a/b/../. reproduction for both fs/promises.rm and fs.rmSync. Compare how each path is handled and determine the intended consistent behavior before checking the surrounding filesystem tests. Done means the two APIs agree for these dot-path cases and regression coverage protects that behavior.