Rephrase whatsnew entry, move tests

Author: MarcoGorelli

doc/source/whatsnew/v1.0.0.rst

@@ -288,6 +288,10 @@ Categorical
 - :meth:`Categorical.searchsorted` and :meth:`CategoricalIndex.searchsorted` now work on unordered categoricals also (:issue:`21667`)
 - Added test to assert roundtripping to parquet with :func:`DataFrame.to_parquet` or :func:`read_parquet` will preserve Categorical dtypes for string types (:issue:`27955`)
 - Changed the error message in :meth:`Categorical.remove_categories` to always show the invalid removals as a set (:issue:`28669`)
+- Using date accessors on a categorical dtyped series of datetimes was not returning a Series (or DataFrame) of the
+  same type as if one used the .str. / .dt. on a Series of that type, e.g. when accessing :meth:`Series.dt.tz_localize` on a
+  :class:`Categorical` with duplicate entries, the accessor was skipping duplicates (:issue: `27952`)
+-
 
 
 Datetimelike

pandas/tests/indexes/test_category.py

@@ -1125,36 +1125,3 @@ def test_engine_type(self, dtype, engine_type):
             ci.values._codes = ci.values._codes.astype("int64")
         assert np.issubdtype(ci.codes.dtype, dtype)
         assert isinstance(ci._engine, engine_type)
-
-    def test_dt_tz_localize(self, tz_aware_fixture):
-        # GH 27952
-        tz = tz_aware_fixture
-        datetimes = pd.Series(
-            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns]"
-        )
-        categorical = datetimes.astype("category")
-        result = categorical.dt.tz_localize(tz)
-        expected = datetimes.dt.tz_localize(tz)
-        tm.assert_series_equal(result, expected)
-
-    def test_dt_tz_convert(self, tz_aware_fixture):
-        # GH 27952
-        tz = tz_aware_fixture
-        datetimes = pd.Series(
-            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns, MET]"
-        )
-        categorical = datetimes.astype("category")
-        result = categorical.dt.tz_convert(tz)
-        expected = datetimes.dt.tz_convert(tz)
-        tm.assert_series_equal(result, expected)
-
-    @pytest.mark.parametrize("accessor", ["year", "month", "day"])
-    def test_dt_other_accessors(self, accessor):
-        # GH 27952
-        datetimes = pd.Series(
-            ["2018-01-01", "2018-01-01", "2019-01-02"], dtype="datetime64[ns]"
-        )
-        categorical = datetimes.astype("category")
-        result = getattr(categorical.dt, accessor)
-        expected = getattr(datetimes.dt, accessor)
-        tm.assert_series_equal(result, expected)

pandas/tests/series/test_datetime_values.py

@@ -344,6 +344,72 @@ def test_dt_namespace_accessor_categorical(self):
         expected = Series([2017, 2017, 2018, 2018], name="foo")
         tm.assert_series_equal(result, expected)
 
+    def test_dt_tz_localize(self, tz_aware_fixture):
+        # GH 27952
+        tz = tz_aware_fixture
+        datetimes = pd.Series(
+            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns]"
+        )
+        categorical = datetimes.astype("category")
+        result = categorical.dt.tz_localize(tz)
+        expected = datetimes.dt.tz_localize(tz)
+        tm.assert_series_equal(result, expected)
+
+    def test_dt_tz_convert(self, tz_aware_fixture):
+        # GH 27952
+        tz = tz_aware_fixture
+        datetimes = pd.Series(
+            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns, MET]"
+        )
+        categorical = datetimes.astype("category")
+        result = categorical.dt.tz_convert(tz)
+        expected = datetimes.dt.tz_convert(tz)
+        tm.assert_series_equal(result, expected)
+
+    @pytest.mark.parametrize("accessor", ["year", "month", "day"])
+    def test_dt_other_accessors(self, accessor):
+        # GH 27952
+        datetimes = pd.Series(
+            ["2018-01-01", "2018-01-01", "2019-01-02"], dtype="datetime64[ns]"
+        )
+        categorical = datetimes.astype("category")
+        result = getattr(categorical.dt, accessor)
+        expected = getattr(datetimes.dt, accessor)
+        tm.assert_series_equal(result, expected)
+
+    def test_dt_tz_localize(self, tz_aware_fixture):
+        # GH 27952
+        tz = tz_aware_fixture
+        datetimes = pd.Series(
+            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns]"
+        )
+        categorical = datetimes.astype("category")
+        result = categorical.dt.tz_localize(tz)
+        expected = datetimes.dt.tz_localize(tz)
+        tm.assert_series_equal(result, expected)
+
+    def test_dt_tz_convert(self, tz_aware_fixture):
+        # GH 27952
+        tz = tz_aware_fixture
+        datetimes = pd.Series(
+            ["2019-01-01", "2019-01-01", "2019-01-02"], dtype="datetime64[ns, MET]"
+        )
+        categorical = datetimes.astype("category")
+        result = categorical.dt.tz_convert(tz)
+        expected = datetimes.dt.tz_convert(tz)
+        tm.assert_series_equal(result, expected)
+
+    @pytest.mark.parametrize("accessor", ["year", "month", "day"])
+    def test_dt_other_accessors(self, accessor):
+        # GH 27952
+        datetimes = pd.Series(
+            ["2018-01-01", "2018-01-01", "2019-01-02"], dtype="datetime64[ns]"
+        )
+        categorical = datetimes.astype("category")
+        result = getattr(categorical.dt, accessor)
+        expected = getattr(datetimes.dt, accessor)
+        tm.assert_series_equal(result, expected)
+
     def test_dt_accessor_no_new_attributes(self):
         # https://github.com/pandas-dev/pandas/issues/10673
         s = Series(date_range("20130101", periods=5, freq="D"))