dvc.fs.Path.parts wrong results

[jonburdo]

EDIT: This issue will just be for this first problem of handling a sep at the end of a path. I made the windows-style path problem a separate issue #7233

When a path ends with the path sep, the parts function doesn't split. It returns a tuple with a single item:

from dvc.fs.path import Path
Path('/').parts('/a/b/c/')

('/a/b/c',)

A second problem occurs when using windows style paths. We get the sep between the drive and the rest of the path:

Path('\\').parts('c:\\a')

('c:', '\\', 'a')

The first problem could be solved by simply stripping the final sep:

        drive, path = self.flavour.splitdrive(path.rstrip(self.flavour.sep))

but the second problem would still exist.

We should really get these results:

Path('/').parts('/a/b/c/')

('/', 'a', 'b', 'c')

and

Path('\\').parts('c:\\a')

('c:', 'a')

Note the second case is still a little different from pathlib, which would include the sep with the drive:

from pathlib import PureWindowsPath
PureWindowsPath('c:\\a').parts

('c:\\', 'a')

but this is probably more in-line with fsspec, which basically treats the drive letter as the first element of a relative path:

fsspec.AbstractFileSystem._parent('c:/a')

'c:'

version info:

DVC version: 2.9.4.dev28+gd90fe54d.d20220106 
---------------------------------
Platform: Python 3.10.1 on Linux-5.15.11-arch2-1-x86_64-with-glibc2.33
Supports:
	azure (adlfs = 2021.10.0, knack = 0.9.0, azure-identity = 1.7.1),
	gdrive (pydrive2 = 1.10.0),
	gs (gcsfs = 2021.11.1),
	hdfs (fsspec = 2021.11.1, pyarrow = 6.0.1),
	webhdfs (fsspec = 2021.11.1),
	http (aiohttp = 3.8.1, aiohttp-retry = 2.4.6),
	https (aiohttp = 3.8.1, aiohttp-retry = 2.4.6),
	s3 (s3fs = 2021.11.1, boto3 = 1.19.8),
	ssh (sshfs = 2021.11.2),
	oss (ossfs = 2021.8.0),
	webdav (webdav4 = 0.9.3),
	webdavs (webdav4 = 0.9.3)
Cache types: <https://error.dvc.org/no-dvc-cache>
Caches: local
Remotes: https
Workspace directory: btrfs on /dev/mapper/nvme0n1p3_crypt
Repo: dvc, git