fix: check for non-int 0 fill values

[ilan-gold]

A bit of an "oops" from me, but hopefully this is more robust (than #3082)! It worked for my one example but testing this without using a spy object seems impossible (happy to contribute that though, or some other test).

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.rst
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.54%. Comparing base (a26926c) to head (8c3fa27).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3345   +/-   ##
=======================================
  Coverage   94.54%   94.54%           
=======================================
  Files          78       78           
  Lines        9423     9424    +1     
=======================================
+ Hits         8909     8910    +1     
  Misses        514      514           

Files with missing lines	Coverage Δ
src/zarr/core/buffer/cpu.py	100.00% <100.00%> (ø)

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[d-v-b]

to test this, could we perhaps patch np.full and np.zeros to raise exceptions, that you would then catch in the test? I'm thinking there would be 2 test functions, 1 testing the various inputs that should hit the np.full branch, and another testing the various inputs that should hit the np.zeros branch. This could also work for a single test function that internally checks which numpy routine the input scalar should trigger

[dstansby]

Looks good to me - needs a release note entry, and I left one suggestion to improve the test too.

[dstansby]

Suggested change

	@pytest.mark.parametrize("fill_value", [None, 0, 1])
	@pytest.mark.parametrize("fill_value", [None, 0, 0.0, 1])

Worth explicitly including a float here?

[ilan-gold]

I've done some digging into this topic, I'll post in a bit but I would like to hold off on merging for a bit.