subsumes fails in case insensitive file systems

[salva]

On Windows, where file systems are usually case insensitive, Tiny::Path::subsumes doesn't take that fact into account.

 path('C:\\WINDOWS')->subsumes('C:\\Windows\\system32')    --> fail
 path('C:\\windows')->subsumes('c:\\windows\\system32')    --> ok (note "C:" Vs "c:")

A workaround could be to use realpath, but it doesn't adjust the case accordingly with the file system. For instance:

path('c:\\windows')->realpath eq path('c:\\WINDOWS')->realpath --> fail

It this behavior is not fixed, at least if should be documented.

[salva]

I have found that relative handles case insensitiveness correctly:

path("c:\\WiNdOwS\\System32")->relative("C:\\windows\\")    ---> 'System32'

[xdg]

Does this patch fix subsumes: https://gist.github.com/xdg/55fcb8ded88bce5073e1888c55cf4d3c

[salva]

That fixes the issue for most cases including the one affecting me, but note that case-sensitiveness is not a property of the operating system but of the file system. So, there is a very edge case where subsume would report a false positive once that patch is applied.

For instance, a case sensitive file system for Windows I use almost daily is the VirtualBox shared folders one which I use to mount file systems from my main host Linux machine into guest Windows virtual machines.

Anyway, I am not saying you should fix that, just want to make you aware that case exists!

[xdg]

It's a hard to problem to address efficiently in general.

E.g. given a directory you don't have write access to, how do you tell if it's on a case-sensitive filesystem or not?

Maybe some general documentation about it would be a good idea.

[salva]

E.g. given a directory you don't have write access to, how do you tell if it's on a case-sensitive filesystem or not?

There is a different approach for that: you can use Win32::GetLongPathName($path) to get the canonical file name as stored in the file system. Though, that only works for file/directories that already exist on the file system.

IMO, a good compromise would be to leave subsumes as it is and make realpath call GetLongPathName under the hood. subsumes is already documented to be dumb, not resolving symbolic links or relative paths so, case sensitiveness could also be added to that list. And it makes perfect sense to have realpath return the name as stored in the file system.

Other alternative that occurs to me, is to add shortpath and longpath methods into Path::Tiny (which would do nothing on non-windows systems), and let the user decide when to call them.

[xdg]

There's something appealing in that solution -- but since relative handles case insensitivity (albeit crudely), I sort of feel like subsumes ought to do the same.

Another approach -- possibly for both subsumes and relative -- might be to default to case insensitivity on Win32, but provide a force_case_sensitive option that users can pass for special cases.