TST: fix tm.to_array nullable handling (#44884)

Author: jbrockmendel

pandas/_testing/__init__.py

@@ -28,17 +28,12 @@
 from pandas._typing import Dtype
 
 from pandas.core.dtypes.common import (
-    is_datetime64_dtype,
-    is_datetime64tz_dtype,
     is_float_dtype,
     is_integer_dtype,
-    is_period_dtype,
     is_sequence,
-    is_timedelta64_dtype,
     is_unsigned_integer_dtype,
     pandas_dtype,
 )
-from pandas.core.dtypes.dtypes import IntervalDtype
 
 import pandas as pd
 from pandas import (
@@ -112,14 +107,11 @@
 )
 from pandas.core.arrays import (
     BaseMaskedArray,
-    DatetimeArray,
     ExtensionArray,
     PandasArray,
-    PeriodArray,
-    TimedeltaArray,
-    period_array,
 )
 from pandas.core.arrays._mixins import NDArrayBackedExtensionArray
+from pandas.core.construction import extract_array
 
 if TYPE_CHECKING:
     from pandas import (
@@ -268,13 +260,6 @@ def box_expected(expected, box_cls, transpose=True):
             #  single-row special cases in datetime arithmetic
             expected = expected.T
             expected = pd.concat([expected] * 2, ignore_index=True)
-    elif box_cls is PeriodArray:
-        # the PeriodArray constructor is not as flexible as period_array
-        expected = period_array(expected)
-    elif box_cls is DatetimeArray:
-        expected = DatetimeArray(expected)
-    elif box_cls is TimedeltaArray:
-        expected = TimedeltaArray(expected)
     elif box_cls is np.ndarray or box_cls is np.array:
         expected = np.array(expected)
     elif box_cls is to_array:
@@ -285,21 +270,16 @@ def box_expected(expected, box_cls, transpose=True):
 
 
 def to_array(obj):
+    """
+    Similar to pd.array, but does not cast numpy dtypes to nullable dtypes.
+    """
     # temporary implementation until we get pd.array in place
     dtype = getattr(obj, "dtype", None)
 
-    if is_period_dtype(dtype):
-        return period_array(obj)
-    elif is_datetime64_dtype(dtype) or is_datetime64tz_dtype(dtype):
-        return DatetimeArray._from_sequence(obj)
-    elif is_timedelta64_dtype(dtype):
-        return TimedeltaArray._from_sequence(obj)
-    elif isinstance(obj, pd.core.arrays.BooleanArray):
-        return obj
-    elif isinstance(dtype, IntervalDtype):
-        return pd.core.arrays.IntervalArray(obj)
-    else:
-        return np.array(obj)
+    if dtype is None:
+        return np.asarray(obj)
+
+    return extract_array(obj, extract_numpy=True)
 
 
 # -----------------------------------------------------------------------------

pandas/tests/arithmetic/test_numeric.py

@@ -1400,11 +1400,15 @@ def test_integer_array_add_list_like(
     if Series == box_pandas_1d_array:
         expected = Series(expected_data, dtype="Int64")
     elif Series == box_1d_array:
-        expected = Series(expected_data, dtype="object")
+        if box_pandas_1d_array is tm.to_array:
+            expected = Series(expected_data, dtype="Int64")
+        else:
+            expected = Series(expected_data, dtype="object")
     elif Index in (box_pandas_1d_array, box_1d_array):
         expected = Int64Index(expected_data)
     else:
-        expected = np.array(expected_data, dtype="object")
+        # box_pandas_1d_array is tm.to_array; preserves IntegerArray
+        expected = array(expected_data, dtype="Int64")
 
     tm.assert_equal(left, expected)
     tm.assert_equal(right, expected)