BUG: preserve DTA/TDA+timedeltalike scalar with mismatched resos (#48923)

* BUG: Timedelta.__new__

* remove assertion

* GH refs

* API: Timedelta(td64_obj) retain resolution

* API: Timedelta constructor pytimedelta, Tick preserve reso

* STYLE: fix pylint style checks for inherit-non-class. (#48897)

* fix pylint for non-class-inherit and add pre-commit changes

* move ExtensionArraySupportsAnyAll to below ExtensionArray

* move if TYPE_CHECKING back up to line 94

* remove erroneous space

* BUG: preserve DTA/TDA+timedeltalike scalar with mismatched resos

* merge main

* remove debugging variable

Co-authored-by: Kostya Farber <73378227+kostyafarber@users.noreply.github.com>

Author: jbrockmendel

pandas/tests/arrays/test_datetimes.py

@@ -1,13 +1,17 @@
 """
 Tests for DatetimeArray
 """
+from datetime import timedelta
 import operator
 
 import numpy as np
 import pytest
 
 from pandas._libs.tslibs import tz_compare
-from pandas._libs.tslibs.dtypes import NpyDatetimeUnit
+from pandas._libs.tslibs.dtypes import (
+    NpyDatetimeUnit,
+    npy_unit_to_abbrev,
+)
 
 from pandas.core.dtypes.dtypes import DatetimeTZDtype
 
@@ -221,6 +225,35 @@ def test_add_mismatched_reso_doesnt_downcast(self):
         #  (so we _could_ downcast to unit="s"), we do not.
         assert res._unit == "us"
 
+    @pytest.mark.parametrize(
+        "scalar",
+        [
+            timedelta(hours=2),
+            pd.Timedelta(hours=2),
+            np.timedelta64(2, "h"),
+            np.timedelta64(2 * 3600 * 1000, "ms"),
+            pd.offsets.Minute(120),
+            pd.offsets.Hour(2),
+        ],
+    )
+    def test_add_timedeltalike_scalar_mismatched_reso(self, dta_dti, scalar):
+        dta, dti = dta_dti
+
+        td = pd.Timedelta(scalar)
+        exp_reso = max(dta._reso, td._reso)
+        exp_unit = npy_unit_to_abbrev(exp_reso)
+
+        expected = (dti + td)._data._as_unit(exp_unit)
+        result = dta + scalar
+        tm.assert_extension_array_equal(result, expected)
+
+        result = scalar + dta
+        tm.assert_extension_array_equal(result, expected)
+
+        expected = (dti - td)._data._as_unit(exp_unit)
+        result = dta - scalar
+        tm.assert_extension_array_equal(result, expected)
+
     def test_sub_datetimelike_scalar_mismatch(self):
         dti = pd.date_range("2016-01-01", periods=3)
         dta = dti._data._as_unit("us")