Backport PR #44356 on branch 1.3.x (Fixed regression in Series.duplicated for categorical dtype with bool categories)

doc/source/whatsnew/v1.3.5.rst

@@ -16,6 +16,7 @@ Fixed regressions
 ~~~~~~~~~~~~~~~~~
 - Fixed regression in :meth:`Series.equals` when comparing floats with dtype object to None (:issue:`44190`)
 - Fixed performance regression in :func:`read_csv` (:issue:`44106`)
+- Fixed regression in :meth:`Series.duplicated` and :meth:`Series.drop_duplicates` when Series has :class:`Categorical` dtype with boolean categories (:issue:`44351`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/algorithms.py

@@ -139,7 +139,7 @@ def _ensure_data(values: ArrayLike) -> tuple[np.ndarray, DtypeObj]:
             # i.e. all-bool Categorical, BooleanArray
             try:
                 return np.asarray(values).astype("uint8", copy=False), values.dtype
-            except TypeError:
+            except (TypeError, ValueError):
                 # GH#42107 we have pd.NAs present
                 return np.asarray(values), values.dtype
 

pandas/tests/series/methods/test_drop_duplicates.py

@@ -2,6 +2,7 @@
 import pytest
 
 from pandas import (
+    NA,
     Categorical,
     Series,
 )
@@ -224,6 +225,20 @@ def test_drop_duplicates_categorical_bool(self, ordered):
         assert return_value is None
         tm.assert_series_equal(sc, tc[~expected])
 
+    def test_drop_duplicates_categorical_bool_na(self):
+        # GH#44351
+        ser = Series(
+            Categorical(
+                [True, False, True, False, NA], categories=[True, False], ordered=True
+            )
+        )
+        result = ser.drop_duplicates()
+        expected = Series(
+            Categorical([True, False, np.nan], categories=[True, False], ordered=True),
+            index=[0, 1, 4],
+        )
+        tm.assert_series_equal(result, expected)
+
 
 def test_drop_duplicates_pos_args_deprecation():
     # GH#41485

pandas/tests/series/methods/test_duplicated.py

@@ -1,7 +1,11 @@
 import numpy as np
 import pytest
 
-from pandas import Series
+from pandas import (
+    NA,
+    Categorical,
+    Series,
+)
 import pandas._testing as tm
 
 
@@ -33,3 +37,15 @@ def test_duplicated_nan_none(keep, expected):
 
     result = ser.duplicated(keep=keep)
     tm.assert_series_equal(result, expected)
+
+
+def test_duplicated_categorical_bool_na():
+    # GH#44351
+    ser = Series(
+        Categorical(
+            [True, False, True, False, NA], categories=[True, False], ordered=True
+        )
+    )
+    result = ser.duplicated()
+    expected = Series([False, False, True, True, False])
+    tm.assert_series_equal(result, expected)