If the ValueError is raised by if not path: check, the falsy values 0 and [] will also raise the same ValueError, which is also strange. Maybe we can change the check to if path == "".

No we can not, that doesn't work for Pathlike objects nor bytes.

@serhiy-storchaka can we back port this to 3.12? It's a pure bug fix.

GH-119388 is a backport of this pull request to the 3.12 branch.

I do not think this is a bug fix. Normally you should not pass None to relpath(), so this does not affect most of applications. If for some reasons you passed an argument of wrong type without checking it, and handle the resulting ValueError, changing the exception type to TypeError is a breaking change. Even if it is right in the long run, it should not be done is the bugfix release.

Thanks, closed the pull request.