Add Zarr 3 support

[rschmunk]

Versions impacted by the bug

5.10 snapshot

What went wrong?

Following the commit of #1447 earlier today adding support for the blosc filter (fixing #1103), I tried opening a Zarr data product that uses it and the result was good and bad.

• I grabbed a fresh ZIP download of the 5.10 SNAPSHOT code (2025-01-16).
• Modified the build.gradle.kts file so that the netcdfAll build includes netcdfAll(project(":libblosc2-native")) in addition to netcdfAll(project(":cdm-zarr"))
• Built a netcdfAll jar.
• Built Panoply with that jar.

I downloaded a fresh copy of the Zarr data product from my office website and tried opening it. Panoply did so, but said that the Zarr data store had no content. I took a look inside and found that there were no .zattrs, .zgroup, or .zmetadata metadata files, but there were zarr.json metadata files. So that's the bad news.

I poked about in my sample_data directory and found that I still had a copy of that data product from late 2023 and I tried opening that data store. Success! Got a nice clean plot of the data.

Closer examination indicates that the "problem" data store is using Zarr 3, while the one that I was able to plot used Zarr 2. If I understand things correctly, Zarr 3 was released Jan 2025, or at least Python tools for reading it were released then.

Sample Zarr 3 store that I could not read is here (31 MB).

Relevant stack trace

Relevant log messages

No response

If you have an example file that you can share, please attach it to this issue.

If so, may we include it in our test datasets to help ensure the bug does not return once fixed?
Note: the test datasets are publicly accessible without restriction.

N/A

Code of Conduct

• I agree to follow the UCAR/Unidata Code of Conduct

[lesserwhirls]

Yep, at this point we only support Zarr v2 (and not with the consolidated metadata addition). Consolidated metadata for v2 is on the todo list, and not sure what it would take to get v3 support at this point.