Unexpected warning when adding arrays with non-matching coordinates

[David-Elias Künstle]

Describe the bug
Unexpected and wrong warning when creating an "empty" sparse array.
It happens, for example, internally, when adding two arrays without matching coordinates.

To Reproduce

import warnings
import sparse
import numpy as np

with warnings.catch_warnings():
    warnings.simplefilter("always")
    a = sparse.COO(np.array([[1], [1]]), np.array([1]), shape=(5, 5))
    b = sparse.COO(np.array([[2], [2]]), np.array([1]), shape=(5, 5))
    a + b  # triggers a warning

    # ... internally caused by ...
    sparse.COO(np.empty((4, 0)), np.array([]), shape=(5, 5))
    # see _umath.py: matched_arrays = [ ...

Output

DeprecationWarning: coords should be an ndarray. This will raise a ValueError in the future.

Expected behavior
No warning.

System

• OS and version: Ubuntu
• sparse version: 0.14.0
• NumPy version (np.__version__): 1.23.5
• Numba version (numba.__version__): 0.56.4

[Hameer Abbasi]

Thanks for the report! Could you reproduce on the development version by any chance?

[Hameer Abbasi]

This should already have been fixed by #581.

[David-Elias Künstle]

Thanks! Yes, #581 did the job.