BUG: Remove special-casing for Python date objects in DatetimeIndex.get_indexer and update whatsnew note (#62158)

Author: Aniketsy

doc/source/whatsnew/v3.0.0.rst

@@ -889,6 +889,8 @@ Datetimelike
 - Bug in constructing arrays with :class:`ArrowDtype` with ``timestamp`` type incorrectly allowing ``Decimal("NaN")`` (:issue:`61773`)
 - Bug in constructing arrays with a timezone-aware :class:`ArrowDtype` from timezone-naive datetime objects incorrectly treating those as UTC times instead of wall times like :class:`DatetimeTZDtype` (:issue:`61775`)
 - Bug in setting scalar values with mismatched resolution into arrays with non-nanosecond ``datetime64``, ``timedelta64`` or :class:`DatetimeTZDtype` incorrectly truncating those scalars (:issue:`56410`)
+- Removed the special casing for sequences of Python ``date`` objects in ``DatetimeIndex.get_indexer`` and related indexing logic.
+  Indexing a ``DatetimeIndex`` with Python ``date`` objects now behaves consistently with other types. (:issue:`62158`)
 
 Timedelta
 ^^^^^^^^^

pandas/tests/indexes/datetimes/test_indexing.py

@@ -514,6 +514,7 @@ def test_contains_nonunique(self, vals):
 
 class TestGetIndexer:
     def test_get_indexer_date_objs(self):
+        # Behavior for get_indexer with date objects changed in GH#62158.
         rng = date_range("1/1/2000", periods=20)
 
         result = rng.get_indexer(rng.map(lambda x: x.date()))

pandas/tests/reshape/merge/test_merge.py

@@ -2132,17 +2132,17 @@ def test_dtype_on_categorical_dates(self):
 
         expected_outer = DataFrame(
             [
-                [date(2001, 1, 1), 1.1, 1.3],
-                [date(2001, 1, 2), 1.3, np.nan],
-                [date(2001, 1, 3), np.nan, 1.4],
+                [pd.Timestamp("2001-01-01").date(), 1.1, 1.3],
+                [pd.Timestamp("2001-01-02").date(), 1.3, np.nan],
+                [pd.Timestamp("2001-01-03").date(), np.nan, 1.4],
             ],
             columns=["date", "num2", "num4"],
         )
         result_outer = merge(df, df2, how="outer", on=["date"])
         tm.assert_frame_equal(result_outer, expected_outer)
 
         expected_inner = DataFrame(
-            [[date(2001, 1, 1), 1.1, 1.3]],
+            [[pd.Timestamp("2001-01-01").date(), 1.1, 1.3]],
             columns=["date", "num2", "num4"],
         )
         result_inner = merge(df, df2, how="inner", on=["date"])

pandas/tests/series/test_arithmetic.py

@@ -763,8 +763,7 @@ def test_align_date_objects_with_datetimeindex(self):
 
         ts_slice = ts[5:]
         ts2 = ts_slice.copy()
-        # Explicitly convert date objects to Timestamps for alignment
-        ts2.index = [pd.Timestamp(x.date()) for x in ts2.index]
+        ts2.index = [x.date() for x in ts2.index]
 
         result = ts + ts2
         result2 = ts2 + ts