BUG: fix Sparse reduction (#27890)

* BUG: fix Sparse reduction

Author: jbrockmendel

doc/source/whatsnew/v0.25.1.rst

@@ -133,7 +133,7 @@ Reshaping
 
 Sparse
 ^^^^^^
-
+- Bug in reductions for :class:`Series` with Sparse dtypes (:issue:`27080`)
 -
 -
 -

pandas/core/arrays/sparse.py

@@ -1693,6 +1693,9 @@ def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
                     for sp_value, fv in zip(sp_values, fill_value)
                 )
                 return arrays
+            elif is_scalar(sp_values):
+                # e.g. reductions
+                return sp_values
 
             return self._simple_new(
                 sp_values, self.sp_index, SparseDtype(sp_values.dtype, fill_value)

pandas/tests/series/test_ufunc.py

@@ -252,10 +252,7 @@ def __add__(self, other):
     "values",
     [
         pd.array([1, 3, 2]),
-        pytest.param(
-            pd.array([1, 10, 0], dtype="Sparse[int]"),
-            marks=pytest.mark.xfail(resason="GH-27080. Bug in SparseArray"),
-        ),
+        pd.array([1, 10, 0], dtype="Sparse[int]"),
         pd.to_datetime(["2000", "2010", "2001"]),
         pd.to_datetime(["2000", "2010", "2001"]).tz_localize("CET"),
         pd.to_datetime(["2000", "2010", "2001"]).to_period(freq="D"),