Zarr ZipStore versus DirectoryStore: ZipStore requires .close()

I was saving my dataset into a ZipStore -- apparently succesfully -- but then I couldn't reopen them.

The issue appears to be that a regular DirectoryStore behaves a little differently: it doesn't need to be closed, while a ZipStore.

(I'm not sure how this relates to #2586, the remarks there don't appear to be applicable anymore.)

MCVE Code Sample

This errors:

import xarray as xr
import zarr

# works as expected 
ds = xr.Dataset({'foo': [2,3,4], 'bar': ('x', [1, 2]), 'baz': 3.14})
ds.to_zarr(zarr.DirectoryStore("test.zarr"))
print(xr.open_zarr(zarr.DirectoryStore("test.zarr")))

# error with ValueError "group not found at path ''
ds.to_zarr(zarr.ZipStore("test.zip"))
print(xr.open_zarr(zarr.ZipStore("test.zip")))

Calling close, or using with does the trick:

store = zarr.ZipStore("test2.zip")
ds.to_zarr(store)
store.close()
print(xr.open_zarr(zarr.ZipStore("test2.zip")))

with zarr.ZipStore("test3.zip") as store:
     ds.to_zarr(store)
print(xr.open_zarr(zarr.ZipStore("test3.zip")))

Expected Output

I think it would be preferable to close the ZipStore in this case. But I might be missing something?

Problem Description

Because to_zarr works in this situation with a DirectoryStore, it's easy to assume a ZipStore will work similarly. However, I couldn't get it to read my data back in this case.

Versions

Start by running the MCVE comparing DirectoryStore and ZipStore, focusing on ds.to_zarr(), xr.open_zarr(), and ZipStore.close(). Trace the store lifecycle used by these entry points and add or update a regression test for reopening the saved dataset. Done means the intended close behavior is covered and the ZipStore example works consistently.