> For example, if we've opened an HSM reparse point, we must reopen to let
> the file-system filter driver implement its semantics to replace the
> reparse point with the real file from auxiliary storage and complete the
> request. That is the stat() result I want when I say stat(filename,
> follow_symlinks=False) or lstat(filename), because this file is not a
> symlink. It's implicitly just the file to end users -- despite whatever
> backend tricks are being played in the kernel to implement other
> behavior such as HSM. Conflating this with a symlink is not right. Lies
> catch up with us. We can't copy it as link via os.symlink and
> os.readlink, and it doesn't get treated like a symlink in API functions.

Okay, I get it now. So we _do_ want to "upgrade" lstat() to stat() when it's not a symlink.

> If you want to add an "open reparse point" parameter ...

I don't want to add any parameters - I want to have predictable and reasonable default behaviour. os.readlink() already exists for "open reparse point" behaviour.

The discussion is only about what os.lstat() returns when you pass in a path to a junction.

> As to mount points, yes, I do think we should always traverse them.
> Please see my extended comment and the follow-up example on GitHub.

I'm still not convinced that this is what we want to do. I don't have a true Linux machine handy to try it out (Python 3.6 and 3.7 on WSL behave exactly like the semantics I'm proposing, but that may just be because it's the Windows kernel below it).

> A mount point is not a link. ismount() and islink() can never both be
> true. Also, a POSIX symlink can never be a directory, which is why we
> make stat() pretend directory symlinks aren't directories. If the user
> wants a link, they can use a symlink that's created by os.symlink,
> mklink, new-item -type SymbolicLink, etc.

ismount() is currently not true for junctions. And I can't find any reference that says that POSIX symlinks can't point to directories, nor any evidence that we suppress symlink-to-directory creation or resolution in Python (also tested on WSL)..