Fix handling of scalar Zarr v3 arrays with None dimension_names

[larsbuntemeyer]

Addiing tiny fix as in xarray (i peeked again :))

• Closes can not open zarr v3 datasets with scalar variables #895
• Tests added
• Tests passing
• Changes are documented in docs/releases.rst

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.31%. Comparing base (3c10c43) to head (97ecf66).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #897      +/-   ##
==========================================
+ Coverage   89.29%   89.31%   +0.02%     
==========================================
  Files          33       33              
  Lines        2036     2040       +4     
==========================================
+ Hits         1818     1822       +4     
  Misses        218      218              

Files with missing lines	Coverage Δ
virtualizarr/manifests/array.py	84.37% <100.00%> (+0.67%)	⬆️

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[larsbuntemeyer]

I'm not sure if this needs testing?

[maxrjones]

Thanks for working on this!

I'm not sure if this needs testing?

Yes, please include a test to make sure the fix isn't lost in the future.

as a suggestion:

def test_to_xarray_scalar_no_dimension_names(array_v3_metadata):
    metadata = array_v3_metadata(
        shape=(),
        chunks=(),
        dimension_names=None,
    )
    manifest = ChunkManifest(entries={"c": {"path": "/foo.nc", "offset": 0, "length": 8}})
    marr = ManifestArray(metadata=metadata, chunkmanifest=manifest)

    vv = marr.to_virtual_variable()
    assert vv.dims == ()


def test_to_xarray_nonscalar_no_dimension_names(array_v3_metadata):
    metadata = array_v3_metadata(
        shape=(5,),
        chunks=(5,),
        dimension_names=None,
    )
    manifest = ChunkManifest(entries={"0": {"path": "/foo.nc", "offset": 0, "length": 40}})
    marr = ManifestArray(metadata=metadata, chunkmanifest=manifest)

    with pytest.raises(ValueError, match="without dimension names"):
        marr.to_virtual_variable()

[maxrjones]

the failures are unrelated so I'm going to approve and merge this. thanks @larsbuntemeyer!

[larsbuntemeyer]

Thanks for the guidance!!