Potentially unexpected behavior on FsspecStore list method

[moradology]

Zarr version

3.0.1

Numcodecs version

0.15.0

Python Version

3.12

Operating System

Mac

Installation

pip

Description

Looks as though this line will have some unexpected results (wiping out all separators) if the empty string is passed as the path during store initialization. The empty string will otherwise work as a way of specifying the current working directory, so this may be undesirable. A couple of resolutions make sense here:

1. guard against empty string path arguments in init
2. modify this line to avoid wholesale replace of self.path + "/" with "":

   zarr-python/src/zarr/storage/_fsspec.py

   Line 344 in e602aa1

   for onefile in (a.replace(self.path + "/", "") for a in allfiles):

Steps to reproduce

Simplest path to reproduction is just to simulate values. These come from a grib in the kerchunk tests:

allfiles = ['.zattrs', '.zgroup', 'refc/.zattrs', 'refc/.zgroup', 'refc/instant.zattrs', 'refc/instant.zgroup', 'refc/instant/atmosphere/.zattrs', 'refc/instant/atmosphere/.zgroup', 'refc/instant/atmosphere/atmosphere/.zarray']
path = ""

# following the logic here https://github.com/zarr-developers/zarr-python/blob/e602aa1d19f26bb06669994231e524c55bcecbeb/src/zarr/storage/_fsspec.py#L344:
for onefile in (a.replace(path + "/", "") for a in allfiles):
    print(onefile)

Additional output

No response

[d-v-b]

yikes. given the number of bugs in stores relating to improper string -> path conversion, I wonder if we need something a bit more robust to guard against this kind of thing.

for example, in this case I think a.replace(path + "/", "") is an attempt to make a relative to path. Besides the obvious solution of using removeprefix instead of replace, we could have a stand-alone make_relative_path(a,b) function that's well tested.

[moradology]

I'll throw together the simpler of the two solutions; if there's an appetite for it, I'll also (or in lieu of this PR) cut a new issue for a reusable make_relative_path function