Added ismount function.

[malmaud]

Equivalent functionality of Python's os.path.ismount function:

os.path.ismount(path)
Return True if pathname path is a mount point: a point in a file system where a different file system has been mounted. The function checks whether path‘s parent, path/.., is on a different device than path, or whether path/.. and path point to the same i-node on the same device — this should detect mount points for all Unix and POSIX variants.

[tkelman]

Seems harmless enough to have, non-exported. Could use a test though.

[jiahao]

+1

[malmaud]

OK, I'll add one.

[nalimilan]

Should probably be exported (see exports.jl) and have some docs (see doc/stdlib/).

[tkelman]

Docs wouldn't hurt, but is this widely used enough to export right away?

[vtjnash]

on linux, this is not necessarily the same as the parent directory.

[nalimilan]

Docs wouldn't hurt, but is this widely used enough to export right away?

If we add it so that people can use it outside of Base, better assume it by exporting the function IMHO. Else this is just pushing people into relying on unofficial APIs. And since Python has it, it's probably worth having too (though it will probably have to move to a separate module when Base is refactored).

[tkelman]

since Python has it, it's probably worth having too (though it will probably have to move to a separate module when Base is refactored).

Sounds good for now, on both counts. We should probably move a bunch of things to an FS module at some point. Doesn't need to be done now unless someone's feeling ambitious.

[malmaud]

@vtjnash Good points. I'll look up the Python implementation and modify mine to be semantically identical.

[ivarne]

I think it is a bad idea to add unexported functions to Base (unless they are an implementation detail of other functions).

I'm also negative to introducing a new function that we expect to move, so if we want a FS module, we should agree on the right name for the module and export it from there.

(sorry for closing, it was not intentional)

[dpsanders]

FS is not a good name for a module - we should respect the package naming rules. Better FileSystem

[tknopp]

I am with @ivarne here. If things in Base are not important enough to be exported, then they should simply not be part of Base.

[tkelman]

FS is not a good name for a module - we should respect the package naming rules. Better FileSystem

Good point. Base.FS happens to already exist, so FS would be the lazy choice. FileSystem would be much better.

I'm also negative to introducing a new function that we expect to move

There's a point there too, but I'm not sure if the onus should be on @malmaud who wants to add one function that has plenty of precedent in other languages, to undertake a major reorganization first. Anyone want to volunteer? I'll add it to my to-do list but might not get to it before 0.4.0.

[malmaud]

Just for reference, this is the Python implementation:

def ismount(path):
    """Test whether a path is a mount point"""
    try:
        s1 = os.lstat(path)
    except OSError:
        # It doesn't exist -- so not a mount point. :-)
        return False
    else:
        # A symlink can never be a mount point
        if stat.S_ISLNK(s1.st_mode):
            return False

    if isinstance(path, bytes):
        parent = join(path, b'..')
    else:
        parent = join(path, '..')
    try:
        s2 = os.lstat(parent)
    except OSError:
        return False

    dev1 = s1.st_dev
    dev2 = s2.st_dev
    if dev1 != dev2:
        return True     # path/.. on a different device as path
    ino1 = s1.st_ino
    ino2 = s2.st_ino
    if ino1 == ino2:
        return True     # path/.. is the same i-node as path
    return False

[malmaud]

Alright, I added docs and make it compatible with the Python definition of a mount point. Not sure how to add a test unless a test can be a fixture that actually mounts a volume. Is that possible in Julia's testing framework?

[StefanKarpinski]

Let's merge this since it seems like reasonable and useful functionality and open a separate issue for figuring out how to test it.