Encoding of coordinate variables fails

[forman]

Encoding of coordinate variables fails when writing datasets to e.g. S3. This error occurs only after with xcube 0.6.1 that introduced the zarr >=2.6.1 requirement. (Which fixed xcube-dev/xcube#360.)

Root cause is obviously that the SH chunk store creates coordinate variables as static values. In this case, both compressor and filters of the array's encoding in .zarray are set to None. This is because we use uncompressed, bytified, static numpy arrays to represent the values for keys that point to coordinate variuables.

A workaround is to use a compressor (although not needed), then that error doesn't appear anymore.

I will file a Zarr issue too...

[AliceBalfanz]

https://github.com/dcs4cop/xcube-sh/blob/master/test/test_reprod_27.py Test failing with xarray=0.19.0