BUG: Array.__setitem__ failing with nullable boolean mask

doc/source/whatsnew/v1.0.1.rst

@@ -70,6 +70,7 @@ Indexing
 
 -
 -
+- Bug where assigning to a :class:`Series` using a IntegerArray / BooleanArray as a mask would raise ``TypeError`` (:issue:`31446`)
 
 Missing
 ^^^^^^^

pandas/core/arrays/boolean.py

@@ -26,6 +26,7 @@
 from pandas.core.dtypes.missing import isna, notna
 
 from pandas.core import nanops, ops
+from pandas.core.indexers import check_array_indexer
 
 from .masked import BaseMaskedArray
 
@@ -369,6 +370,7 @@ def __setitem__(self, key, value):
             value = value[0]
             mask = mask[0]
 
+        key = check_array_indexer(self, key)
         self._data[key] = value
         self._mask[key] = mask
 

pandas/core/arrays/categorical.py

@@ -2073,6 +2073,8 @@ def __setitem__(self, key, value):
 
         lindexer = self.categories.get_indexer(rvalue)
         lindexer = self._maybe_coerce_indexer(lindexer)
+
+        key = check_array_indexer(self, key)
         self._codes[key] = lindexer
 
     def _reverse_indexer(self) -> Dict[Hashable, np.ndarray]:

pandas/core/arrays/datetimelike.py

@@ -601,6 +601,8 @@ def __setitem__(
                 f"or array of those. Got '{type(value).__name__}' instead."
             )
             raise TypeError(msg)
+
+        key = check_array_indexer(self, key)
         self._data[key] = value
         self._maybe_clear_freq()
 

pandas/core/arrays/integer.py

@@ -25,6 +25,7 @@
 from pandas.core.dtypes.missing import isna
 
 from pandas.core import nanops, ops
+from pandas.core.indexers import check_array_indexer
 from pandas.core.ops import invalid_comparison
 from pandas.core.ops.common import unpack_zerodim_and_defer
 from pandas.core.tools.numeric import to_numeric
@@ -414,6 +415,7 @@ def __setitem__(self, key, value):
             value = value[0]
             mask = mask[0]
 
+        key = check_array_indexer(self, key)
         self._data[key] = value
         self._mask[key] = mask
 

pandas/core/arrays/interval.py

@@ -541,6 +541,7 @@ def __setitem__(self, key, value):
                 msg = f"'value' should be an interval type, got {type(value)} instead."
                 raise TypeError(msg)
 
+        key = check_array_indexer(self, key)
         # Need to ensure that left and right are updated atomically, so we're
         # forced to copy, update the copy, and swap in the new values.
         left = self.left.copy(deep=True)

pandas/core/arrays/numpy_.py

@@ -245,6 +245,7 @@ def __getitem__(self, item):
     def __setitem__(self, key, value):
         value = extract_array(value, extract_numpy=True)
 
+        key = check_array_indexer(self, key)
         scalar_key = lib.is_scalar(key)
         scalar_value = lib.is_scalar(value)
 

pandas/core/arrays/string_.py

@@ -15,6 +15,7 @@
 from pandas.core import ops
 from pandas.core.arrays import PandasArray
 from pandas.core.construction import extract_array
+from pandas.core.indexers import check_array_indexer
 from pandas.core.missing import isna
 
 
@@ -224,6 +225,7 @@ def __setitem__(self, key, value):
             # extract_array doesn't extract PandasArray subclasses
             value = value._ndarray
 
+        key = check_array_indexer(self, key)
         scalar_key = lib.is_scalar(key)
         scalar_value = lib.is_scalar(value)
         if scalar_key and not scalar_value:

pandas/tests/arrays/test_integer.py

@@ -1074,6 +1074,23 @@ def test_cut(bins, right, include_lowest):
     tm.assert_categorical_equal(result, expected)
 
 
+def test_array_setitem_nullable_boolean_mask():
+    # GH 31446
+    ser = pd.Series([1, 2], dtype="Int64")
+    result = ser.where(ser > 1)
+    expected = pd.Series([pd.NA, 2], dtype="Int64")
+    tm.assert_series_equal(result, expected)
+
+
+def test_array_setitem():
+    # GH 31446
+    arr = pd.Series([1, 2], dtype="Int64").array
+    arr[arr > 1] = 1
+
+    expected = pd.array([1, 1], dtype="Int64")
+    tm.assert_extension_array_equal(arr, expected)
+
+
 # TODO(jreback) - these need testing / are broken
 
 # shift

pandas/tests/extension/base/setitem.py

@@ -4,6 +4,7 @@
 import pytest
 
 import pandas as pd
+from pandas.core.arrays.numpy_ import PandasDtype
 
 from .base import BaseExtensionTests
 
@@ -195,3 +196,14 @@ def test_setitem_preserves_views(self, data):
         data[0] = data[1]
         assert view1[0] == data[1]
         assert view2[0] == data[1]
+
+    def test_setitem_nullable_mask(self, data):
+        # GH 31446
+        # TODO: there is some issue with PandasArray, therefore,
+        # TODO: skip the setitem test for now, and fix it later
+        if data.dtype != PandasDtype("object"):
+            arr = data[:5]
+            expected = data.take([0, 0, 0, 3, 4])
+            mask = pd.array([True, True, True, False, False])
+            arr[mask] = data[0]
+            self.assert_extension_array_equal(expected, arr)

pandas/tests/extension/decimal/array.py

@@ -11,6 +11,7 @@
 import pandas as pd
 from pandas.api.extensions import no_default, register_extension_dtype
 from pandas.core.arrays import ExtensionArray, ExtensionScalarOpsMixin
+from pandas.core.indexers import check_array_indexer
 
 
 @register_extension_dtype
@@ -138,6 +139,8 @@ def __setitem__(self, key, value):
             value = [decimal.Decimal(v) for v in value]
         else:
             value = decimal.Decimal(value)
+
+        key = check_array_indexer(self, key)
         self._data[key] = value
 
     def __len__(self) -> int: