BUG: SparseArray.min/max skipna (#44829)

Author: jbrockmendel

pandas/core/arrays/sparse/array.py

@@ -1491,69 +1491,76 @@ def mean(self, axis=0, *args, **kwargs):
             nsparse = self.sp_index.ngaps
             return (sp_sum + self.fill_value * nsparse) / (ct + nsparse)
 
-    def max(self, axis: int = 0, *args, **kwargs) -> Scalar:
+    def max(self, *, axis: int | None = None, skipna: bool = True):
         """
-        Max of non-NA/null values
+        Max of array values, ignoring NA values if specified.
 
         Parameters
         ----------
         axis : int, default 0
             Not Used. NumPy compatibility.
-        *args, **kwargs
-            Not Used. NumPy compatibility.
+        skipna : bool, default True
+            Whether to ignore NA values.
 
         Returns
         -------
         scalar
         """
-        nv.validate_max(args, kwargs)
-        return self._min_max("max")
+        nv.validate_minmax_axis(axis, self.ndim)
+        return self._min_max("max", skipna=skipna)
 
-    def min(self, axis: int = 0, *args, **kwargs) -> Scalar:
+    def min(self, *, axis: int | None = None, skipna: bool = True):
         """
-        Min of non-NA/null values
+        Min of array values, ignoring NA values if specified.
 
         Parameters
         ----------
         axis : int, default 0
             Not Used. NumPy compatibility.
-        *args, **kwargs
-            Not Used. NumPy compatibility.
+        skipna : bool, default True
+            Whether to ignore NA values.
 
         Returns
         -------
         scalar
         """
-        nv.validate_min(args, kwargs)
-        return self._min_max("min")
+        nv.validate_minmax_axis(axis, self.ndim)
+        return self._min_max("min", skipna=skipna)
 
-    def _min_max(self, kind: Literal["min", "max"]) -> Scalar:
+    def _min_max(self, kind: Literal["min", "max"], skipna: bool) -> Scalar:
         """
         Min/max of non-NA/null values
 
         Parameters
         ----------
         kind : {"min", "max"}
+        skipna : bool
 
         Returns
         -------
         scalar
         """
         valid_vals = self._valid_sp_values
         has_nonnull_fill_vals = not self._null_fill_value and self.sp_index.ngaps > 0
+
         if len(valid_vals) > 0:
             sp_min_max = getattr(valid_vals, kind)()
 
             # If a non-null fill value is currently present, it might be the min/max
             if has_nonnull_fill_vals:
                 func = max if kind == "max" else min
                 return func(sp_min_max, self.fill_value)
-            else:
+            elif skipna:
+                return sp_min_max
+            elif self.sp_index.ngaps == 0:
+                # No NAs present
                 return sp_min_max
+            else:
+                return na_value_for_dtype(self.dtype.subtype, compat=False)
         elif has_nonnull_fill_vals:
             return self.fill_value
         else:
-            return na_value_for_dtype(self.dtype.subtype)
+            return na_value_for_dtype(self.dtype.subtype, compat=False)
 
     # ------------------------------------------------------------------------
     # Ufuncs

pandas/tests/arrays/sparse/test_array.py

@@ -1387,11 +1387,21 @@ class TestMinMax:
         ],
     )
     def test_nan_fill_value(self, raw_data, max_expected, min_expected):
-        max_result = SparseArray(raw_data).max()
-        min_result = SparseArray(raw_data).min()
+        arr = SparseArray(raw_data)
+        max_result = arr.max()
+        min_result = arr.min()
         assert max_result in max_expected
         assert min_result in min_expected
 
+        max_result = arr.max(skipna=False)
+        min_result = arr.min(skipna=False)
+        if np.isnan(raw_data).any():
+            assert np.isnan(max_result)
+            assert np.isnan(min_result)
+        else:
+            assert max_result in max_expected
+            assert min_result in min_expected
+
     @pytest.mark.parametrize(
         "fill_value,max_expected,min_expected",
         [
@@ -1409,6 +1419,16 @@ def test_fill_value(self, fill_value, max_expected, min_expected):
         min_result = arr.min()
         assert min_result == min_expected
 
+    def test_only_fill_value(self):
+        fv = 100
+        arr = SparseArray(np.array([fv, fv, fv]), dtype=SparseDtype("int", fv))
+        assert len(arr._valid_sp_values) == 0
+
+        assert arr.max() == fv
+        assert arr.min() == fv
+        assert arr.max(skipna=False) == fv
+        assert arr.min(skipna=False) == fv
+
     @pytest.mark.parametrize("func", ["min", "max"])
     @pytest.mark.parametrize("data", [np.array([]), np.array([np.nan, np.nan])])
     @pytest.mark.parametrize(
@@ -1423,7 +1443,8 @@ def test_fill_value(self, fill_value, max_expected, min_expected):
     def test_na_value_if_no_valid_values(self, func, data, dtype, expected):
         arr = SparseArray(data, dtype=dtype)
         result = getattr(arr, func)()
-        if expected == pd.NaT:
-            assert result == pd.NaT
+        if expected is pd.NaT:
+            # TODO: pin down whether we wrap datetime64("NaT")
+            assert result is pd.NaT or np.isnat(result)
         else:
             assert np.isnan(result)