Fixing check_zero_fill_value

sparse/numba_backend/_utils.py

@@ -588,6 +588,8 @@ def check_zero_fill_value(*args, loose=True):
     ValueError: This operation requires zero fill values, but argument 1 had a fill value of 0.5.
     """
     for i, arg in enumerate(args):
+        if arg.size == 0:
+            continue
         if hasattr(arg, "fill_value") and not equivalent(arg.fill_value, _zero_of_dtype(arg.dtype), loose=loose):
             raise ValueError(
                 f"This operation requires zero fill values, but argument {i:d} had a fill value of {arg.fill_value!s}."

sparse/numba_backend/tests/test_coo.py

@@ -6,7 +6,7 @@
 import sparse
 from sparse import COO, DOK
 from sparse.numba_backend._settings import NEP18_ENABLED
-from sparse.numba_backend._utils import assert_eq, html_table, random_value_array
+from sparse.numba_backend._utils import assert_eq, check_zero_fill_value, html_table, random_value_array
 
 import pytest
 
@@ -1918,6 +1918,16 @@ def test_to_invalid_device():
         s.to_device("invalid_device")
 
 
+# regression test for gh-877
+def test_check_zero_fill_value():
+    a = sparse.zeros((1, 0))
+    b = a - sparse.mean(a, axis=1)
+    b @ b.T  # should not raise an error
+    with pytest.raises(ValueError, match="This operation requires zero fill values"):
+        s1 = sparse.random((10,), density=0.5, fill_value=1.0)
+        check_zero_fill_value(s1)
+
+
 # regression test for gh-869
 def test_xH_x():
     Y = np.array([[0, -1j], [+1j, 0]])