fix: detect Zarr v3 format from store files#27
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Thanks for fixing this! I decided to make the next radklim version as zarr3 too, and I just used your branch with: uvx --from "git+https://github.com/mlcast-community/mlcast-dataset-validator@fix/detect-zarr-v3-format" mlcast.validate_dataset source_data radar_precipitation data/dst/hourly/zarr/2001_2024.zarrand the validator now passes 🥳 |
leifdenby
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Looks great! Just need a CHANGELOG update now
The previous approach used `getattr(ds, "zarr_format", 2)` which always defaulted to v2 because xarray does not expose `zarr_format` as a dataset attribute. This caused v3 stores to be misidentified as v2, incorrectly triggering the consolidated metadata check (which does not apply to Zarr v3). The new `_detect_zarr_format()` helper inspects the store on disk: Zarr v3 stores have a `zarr.json` at the root, while v2 stores have `.zgroup`. This works for both local and remote stores via fsspec.
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Summary
getattr(ds, "zarr_format", 2), which always defaulted to v2 because xarray does not exposezarr_formatas a dataset attribute_detect_zarr_format()that inspects the store on disk: v3 stores havezarr.jsonat root, v2 stores have.zgroup. Works for both local and remote stores via fsspecConsiderations
I tested this on a zarr v3 and it works correctly. There is still the question if we want to enforce the presence of consolidated metadata also for zarr v3 altough it is currently an experimental feature and subject to change:
https://zarr.readthedocs.io/en/latest/user-guide/consolidated_metadata/