Extend refspec support to [path] entries (without offset/length)

[maresb]

I'm trying to open a Zarr v2. I couldn't find a good obvious way to do this, so my attempt was:

from kerchunk.zarr import ZarrToZarr
from virtualizarr.xarray import dataset_from_kerchunk_refs

ref = ZarrToZarr(url).translate()
ds = dataset_from_kerchunk_refs(ref)

This fails here in unpacking because kerchunk produces reference entries of the form [path] instead of [path, length, offset].

I was wondering if I could work around this by stating the chunks, and sure enough it worked! (See my second commit.)

I'd love to get some feedback on this, including if there's a better way to open v2 zarrs.

In preparation for my second commit I needed to clean up some types. To make things more precise and clean, I tell a minor lie: that the [path, offset, length] lists are tuples. This was done in the spirit of duck typing, and I'd argue is more semantically accurate. (Not to mention that tuples serialize to lists in JSON.)

• [ ] Closes #xxxx
• [ ] Tests added
• [ ] Tests passing
• [ ] Full type hint coverage
• [ ] Changes are documented in docs/releases.rst
• [ ] New functions/methods are listed in api.rst
• [ ] New functionality has documentation

[maresb]

@TomNicholas, I think I'm ready for another round of review, whenever you are.

[TomNicholas]

Sorry for the slow review @maresb ! Just some very small comments here.

[maresb]

Sorry for the slow review @maresb ! Just some very small comments here.

No worries, no rush, and thanks so much for maintaining!!!

[maresb]

I think I'm all caught up with your comments.

I don't think you're asking for a change regarding the NotImplementedError on inlined data, but I'm not certain about this.

Please let me know if you'd like any further changes, or if you'd like me to rebase.

Thanks @TomNicholas!

[TomNicholas]

I think this looks good, thank you @maresb !