REGR: get_loc for ExtensionEngine not returning bool indexer for na (#48411)

Author: phofl

pandas/_libs/index.pyx

@@ -1061,7 +1061,7 @@ cdef class ExtensionEngine(SharedEngine):
 
     cdef ndarray _get_bool_indexer(self, val):
         if checknull(val):
-            return self.values.isna().view("uint8")
+            return self.values.isna()
 
         try:
             return self.values == val

pandas/tests/indexes/test_indexing.py

@@ -20,6 +20,7 @@
 from pandas.errors import InvalidIndexError
 
 from pandas import (
+    NA,
     DatetimeIndex,
     Index,
     IntervalIndex,
@@ -221,6 +222,13 @@ def test_get_loc_generator(self, index):
             # MultiIndex specifically checks for generator; others for scalar
             index.get_loc(x for x in range(5))
 
+    def test_get_loc_masked_duplicated_na(self):
+        # GH#48411
+        idx = Index([1, 2, NA, NA], dtype="Int64")
+        result = idx.get_loc(NA)
+        expected = np.array([False, False, True, True])
+        tm.assert_numpy_array_equal(result, expected)
+
 
 class TestGetIndexer:
     def test_get_indexer_base(self, index):
@@ -253,6 +261,13 @@ def test_get_indexer_consistency(self, index):
         assert isinstance(indexer, np.ndarray)
         assert indexer.dtype == np.intp
 
+    def test_get_indexer_masked_duplicated_na(self):
+        # GH#48411
+        idx = Index([1, 2, NA, NA], dtype="Int64")
+        result = idx.get_indexer_for(Index([1, NA], dtype="Int64"))
+        expected = np.array([0, 2, 3], dtype=result.dtype)
+        tm.assert_numpy_array_equal(result, expected)
+
 
 class TestConvertSliceIndexer:
     def test_convert_almost_null_slice(self, index):