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Invalid --chunks/--shards arguments to b2nd-to-zarr deletes destination with --force

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
data

Research direction

Start by locating the b2nd-to-zarr command implementation and tracing where it removes the destination with --force relative to its call to zarr.create_array. Reproduce the failure using the shell commands in the issue, including --chunks 30 --shards 50 --force. Done means invalid arguments no longer cause the existing destination to disappear when conversion fails.

Written by the indexing model from the issue text.

Description

Describe the bug
If a user creates a .zarr file using b2nd-to-zarr, then subsequently calls b2nd-to-zarr again with arguments to --chunks and --shards that are invalid, meaning shards % chunks != 0, then b2nd-to-zarr will call shutil.rmtree(dst_path) first and then call zarr.create_array which will fail. I think ideally the converter should throw an error before reaching zarr.create_array about invalid arguments to --chunks and --shards.

To Reproduce
Steps to reproduce the behavior:

Shell commands:

  python -c "import blosc2, numpy as np; blosc2.asarray(np.arange(1000), urlpath='data.b2nd', mode='w')"
  b2nd-to-zarr data.b2nd good.zarr -q && ls good.zarr
  b2nd-to-zarr data.b2nd good.zarr --chunks 30 --shards 50 --force

Output:

Error: Chunk edge length 50 in dimension 0 is not divisible by the shard's inner chunk size 30.

Then

  ls good.zarr

produces

ls: good.zarr: No such file or directory

Expected behavior
good.zarr should still exist even if the converter fails

Desktop:

  • OS: Mac OS Tahoe
  • Version 26.7

Additional context
I think one additional option besides throwing an earlier error message could be writing to a temporary path and then renaming it after success

Dominant language
Python
Stars
211
Forks
66
Avg merge
2d 1h
Merged PRs (30d)
15

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