Don't overwrite codec config values when set.

[dcherian]

A codec doesn't know where it is in the codec pipeline, so it cannot know whether array_spec.dtype should match codec.dtype or not. So I don't think it's appropriate to overwrite or even raise a warning or error.

TODO:

• xref Zarr overwrites codec configuration when creating and opening Arrays zarr-python#2800
• Unit tests and/or doctests in docstrings
• Tests pass locally
• Docstrings and API docs for any new/modified user-facing classes and functions
• Changes documented in docs/release.rst
• Docs build locally
• GitHub Actions CI passes
• Test coverage to 100% (Codecov passes)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.74%. Comparing base (8a0bd3b) to head (56bc88d).
Report is 1 commits behind head on main.

❌ Your project status has failed because the head coverage (99.74%) is below the target coverage (100.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #700      +/-   ##
==========================================
- Coverage   99.78%   99.74%   -0.04%     
==========================================
  Files          63       63              
  Lines        2754     2753       -1     
==========================================
- Hits         2748     2746       -2     
- Misses          6        7       +1     

Files with missing lines	Coverage Δ
numcodecs/tests/test_zarr3.py	100.00% <ø> (ø)
numcodecs/zarr3.py	99.50% <100.00%> (-0.50%)	⬇️

[dstansby]

I requested Norman for a review, since he originally wrote this code. Would be good to add some release notes too to explain what's fixed/changed for users.

[normanrz]

Looks good to me! Thanks!

[dcherian]

Sweet can we release to unbreak Zar?

[d-v-b]

i have no idea how to do a release but we should absolutely do one

[d-v-b]

@dcherian I cut a release with this fix