bug#46397: 27.1; Cannot delete buffer pointing to a file in a path that includes a file

[Paul Eggert]

On 3/6/21 1:36 AM, Eli Zaretskii wrote:
> I'm asking what is the difference, from the file-locking POV, between
> an inaccessible directory and a directory that doesn't exist?

In the former (EACCES) case, it's possible that the lockfile exists but 
Emacs cannot remove it because the user currently lacks permissions to 
an ancestor directory; this serious problem is worth reporting to the user.

In the latter (ENOTDIR) case the lockfile cannot possibly exist, and 
Emacs can treat ENOTDIR differently from EACCES for that reason. It 
makes sense for Emacs to treat ENOTDIR like ENOENT, since in both cases 
the lockfile cannot possibly exist and these are the only two error 
numbers with that property.

It might also make sense to treat ENOTDIR specially (neither like EACCES 
nor like ENOENT) but that's a discussion we haven't had yet, as far as I 
know.

We've spent more time on this ENOENT/ENOTDIR issue than it's worth, so 
feel free to revert my change and install whatever other change you 
like. I'm sure there are lots of ways to fix the underlying problem.