What happened?

I'm using an anemoi-training fork that does not use supporting arrays when calling save_metadata and I get the following error:

[rank0]:   File ".../anemoi-training-downscaling/src/anemoi/training/diagnostics/callbacks/callbacks.py", line 1202, in _save_checkpoint
[rank0]:     save_metadata(inference_checkpoint_filepath, metadata)
[rank0]:   File ".../anemoi-utils/src/anemoi/utils/checkpoints.py", line 235, in save_metadata
[rank0]:     _write_array_to_bytes(supporting_arrays, "", metadata["supporting_arrays_paths"], zipf)
[rank0]:   File ".../anemoi-utils/src/anemoi/utils/checkpoints.py", line 179, in _write_array_to_bytes
[rank0]:     entry["path"],
[rank0]:     ~~~~~^^^^^^^^
[rank0]: KeyError: 'path'

This bug was introduced in #229, in src/anemoi/utils/checkpoints.py:

-       for name, entry in metadata["supporting_arrays_paths"].items():
-           value = supporting_arrays[name]
-           LOG.info(
-               "Saving supporting array `%s` to %s (shape=%s, dtype=%s)",
-               name,
-               entry["path"],
-               entry["shape"],
-               entry["dtype"],
-           )
-           zipf.writestr(entry["path"], value.tobytes())
+       _write_array_to_bytes(supporting_arrays, "", metadata["supporting_arrays_paths"], zipf)

In the old version, if metadata["supporting_arrays_paths"] is empty, entry["path"] is not called.
That's not true anymore in the updated version.

What are the steps to reproduce the bug?

Calling save_metadata with the default supporting_arrays = None argument

Version

commit 9dacd62

Platform (OS and architecture)

Linux uan01 5.14.21-150500.55.49_13.0.56-cray_shasta_c #1 SMP Mon Mar 4 14:19:49 UTC 2024 (9d8355b) x86_64 x86_64 x86_64 GNU/Linux

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Organisation

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