REF: avoid monkeypatch in arrow tests (#54361)

* REF: avoid monkeypatch in arrow tests

* cleanup

Author: jbrockmendel

pandas/tests/extension/test_arrow.py

@@ -863,17 +863,22 @@ def get_op_from_name(self, op_name):
         short_opname = op_name.strip("_")
         if short_opname == "rtruediv":
             # use the numpy version that won't raise on division by zero
-            return lambda x, y: np.divide(y, x)
+
+            def rtruediv(x, y):
+                return np.divide(y, x)
+
+            return rtruediv
         elif short_opname == "rfloordiv":
             return lambda x, y: np.floor_divide(y, x)
 
         return tm.get_op_from_name(op_name)
 
-    def _patch_combine(self, obj, other, op):
+    def _combine(self, obj, other, op):
         # BaseOpsUtil._combine can upcast expected dtype
         # (because it generates expected on python scalars)
         # while ArrowExtensionArray maintains original type
         expected = base.BaseArithmeticOpsTests._combine(self, obj, other, op)
+
         was_frame = False
         if isinstance(expected, pd.DataFrame):
             was_frame = True
@@ -883,10 +888,37 @@ def _patch_combine(self, obj, other, op):
             expected_data = expected
             original_dtype = obj.dtype
 
+        orig_pa_type = original_dtype.pyarrow_dtype
+        if not was_frame and isinstance(other, pd.Series):
+            # i.e. test_arith_series_with_array
+            if not (
+                pa.types.is_floating(orig_pa_type)
+                or (
+                    pa.types.is_integer(orig_pa_type)
+                    and op.__name__ not in ["truediv", "rtruediv"]
+                )
+                or pa.types.is_duration(orig_pa_type)
+                or pa.types.is_timestamp(orig_pa_type)
+                or pa.types.is_date(orig_pa_type)
+                or pa.types.is_decimal(orig_pa_type)
+            ):
+                # base class _combine always returns int64, while
+                #  ArrowExtensionArray does not upcast
+                return expected
+        elif not (
+            (op is operator.floordiv and pa.types.is_integer(orig_pa_type))
+            or pa.types.is_duration(orig_pa_type)
+            or pa.types.is_timestamp(orig_pa_type)
+            or pa.types.is_date(orig_pa_type)
+            or pa.types.is_decimal(orig_pa_type)
+        ):
+            # base class _combine always returns int64, while
+            #  ArrowExtensionArray does not upcast
+            return expected
+
         pa_expected = pa.array(expected_data._values)
 
         if pa.types.is_duration(pa_expected.type):
-            orig_pa_type = original_dtype.pyarrow_dtype
             if pa.types.is_date(orig_pa_type):
                 if pa.types.is_date64(orig_pa_type):
                     # TODO: why is this different vs date32?
@@ -907,7 +939,7 @@ def _patch_combine(self, obj, other, op):
             pa_expected = pa_expected.cast(f"duration[{unit}]")
 
         elif pa.types.is_decimal(pa_expected.type) and pa.types.is_decimal(
-            original_dtype.pyarrow_dtype
+            orig_pa_type
         ):
             # decimal precision can resize in the result type depending on data
             # just compare the float values
@@ -929,7 +961,7 @@ def _patch_combine(self, obj, other, op):
             return expected.astype(alt_dtype)
 
         else:
-            pa_expected = pa_expected.cast(original_dtype.pyarrow_dtype)
+            pa_expected = pa_expected.cast(orig_pa_type)
 
         pd_expected = type(expected_data._values)(pa_expected)
         if was_frame:
@@ -1043,9 +1075,7 @@ def _get_arith_xfail_marker(self, opname, pa_dtype):
 
         return mark
 
-    def test_arith_series_with_scalar(
-        self, data, all_arithmetic_operators, request, monkeypatch
-    ):
+    def test_arith_series_with_scalar(self, data, all_arithmetic_operators, request):
         pa_dtype = data.dtype.pyarrow_dtype
 
         if all_arithmetic_operators == "__rmod__" and (
@@ -1061,24 +1091,9 @@ def test_arith_series_with_scalar(
         if mark is not None:
             request.node.add_marker(mark)
 
-        if (
-            (
-                all_arithmetic_operators == "__floordiv__"
-                and pa.types.is_integer(pa_dtype)
-            )
-            or pa.types.is_duration(pa_dtype)
-            or pa.types.is_timestamp(pa_dtype)
-            or pa.types.is_date(pa_dtype)
-            or pa.types.is_decimal(pa_dtype)
-        ):
-            # BaseOpsUtil._combine always returns int64, while ArrowExtensionArray does
-            # not upcast
-            monkeypatch.setattr(TestBaseArithmeticOps, "_combine", self._patch_combine)
         super().test_arith_series_with_scalar(data, all_arithmetic_operators)
 
-    def test_arith_frame_with_scalar(
-        self, data, all_arithmetic_operators, request, monkeypatch
-    ):
+    def test_arith_frame_with_scalar(self, data, all_arithmetic_operators, request):
         pa_dtype = data.dtype.pyarrow_dtype
 
         if all_arithmetic_operators == "__rmod__" and (
@@ -1094,24 +1109,9 @@ def test_arith_frame_with_scalar(
         if mark is not None:
             request.node.add_marker(mark)
 
-        if (
-            (
-                all_arithmetic_operators == "__floordiv__"
-                and pa.types.is_integer(pa_dtype)
-            )
-            or pa.types.is_duration(pa_dtype)
-            or pa.types.is_timestamp(pa_dtype)
-            or pa.types.is_date(pa_dtype)
-            or pa.types.is_decimal(pa_dtype)
-        ):
-            # BaseOpsUtil._combine always returns int64, while ArrowExtensionArray does
-            # not upcast
-            monkeypatch.setattr(TestBaseArithmeticOps, "_combine", self._patch_combine)
         super().test_arith_frame_with_scalar(data, all_arithmetic_operators)
 
-    def test_arith_series_with_array(
-        self, data, all_arithmetic_operators, request, monkeypatch
-    ):
+    def test_arith_series_with_array(self, data, all_arithmetic_operators, request):
         pa_dtype = data.dtype.pyarrow_dtype
 
         self.series_array_exc = self._get_scalar_exception(
@@ -1147,18 +1147,6 @@ def test_arith_series_with_array(
         # since ser.iloc[0] is a python scalar
         other = pd.Series(pd.array([ser.iloc[0]] * len(ser), dtype=data.dtype))
 
-        if (
-            pa.types.is_floating(pa_dtype)
-            or (
-                pa.types.is_integer(pa_dtype)
-                and all_arithmetic_operators not in ["__truediv__", "__rtruediv__"]
-            )
-            or pa.types.is_duration(pa_dtype)
-            or pa.types.is_timestamp(pa_dtype)
-            or pa.types.is_date(pa_dtype)
-            or pa.types.is_decimal(pa_dtype)
-        ):
-            monkeypatch.setattr(TestBaseArithmeticOps, "_combine", self._patch_combine)
         self.check_opname(ser, op_name, other, exc=self.series_array_exc)
 
     def test_add_series_with_extension_array(self, data, request):