Bug in iloc.setitem orienting IntegerArray into the wrong direction (#41288)

Author: phofl

pandas/core/indexers.py

@@ -164,7 +164,7 @@ def check_setitem_lengths(indexer, value, values) -> bool:
         #  a) not necessarily 1-D indexers, e.g. tuple
         #  b) boolean indexers e.g. BoolArray
         if is_list_like(value):
-            if len(indexer) != len(value):
+            if len(indexer) != len(value) and values.ndim == 1:
                 # boolean with truth values == len of the value is ok too
                 if not (
                     isinstance(indexer, np.ndarray)

pandas/core/internals/blocks.py

@@ -970,12 +970,7 @@ def setitem(self, indexer, value):
             values[indexer] = value
 
         elif is_ea_value:
-            # GH#38952
-            if values.ndim == 1:
-                values[indexer] = value
-            else:
-                # TODO(EA2D): special case not needed with 2D EA
-                values[indexer] = value.to_numpy(values.dtype).reshape(-1, 1)
+            values[indexer] = value
 
         else:
             # error: Argument 1 to "setitem_datetimelike_compat" has incompatible type

pandas/tests/frame/indexing/test_setitem.py

@@ -18,6 +18,7 @@
     PeriodDtype,
 )
 
+import pandas as pd
 from pandas import (
     Categorical,
     DataFrame,
@@ -792,22 +793,29 @@ def test_setitem_slice_position(self):
         tm.assert_frame_equal(df, expected)
 
     @pytest.mark.parametrize("indexer", [tm.setitem, tm.iloc])
-    @pytest.mark.parametrize("box", [Series, np.array, list])
+    @pytest.mark.parametrize("box", [Series, np.array, list, pd.array])
     @pytest.mark.parametrize("n", [1, 2, 3])
-    def test_setitem_broadcasting_rhs(self, n, box, indexer):
+    def test_setitem_slice_indexer_broadcasting_rhs(self, n, box, indexer):
         # GH#40440
-        # TODO: Add pandas array as box after GH#40933 is fixed
         df = DataFrame([[1, 3, 5]] + [[2, 4, 6]] * n, columns=["a", "b", "c"])
         indexer(df)[1:] = box([10, 11, 12])
         expected = DataFrame([[1, 3, 5]] + [[10, 11, 12]] * n, columns=["a", "b", "c"])
         tm.assert_frame_equal(df, expected)
 
+    @pytest.mark.parametrize("box", [Series, np.array, list, pd.array])
+    @pytest.mark.parametrize("n", [1, 2, 3])
+    def test_setitem_list_indexer_broadcasting_rhs(self, n, box):
+        # GH#40440
+        df = DataFrame([[1, 3, 5]] + [[2, 4, 6]] * n, columns=["a", "b", "c"])
+        df.iloc[list(range(1, n + 1))] = box([10, 11, 12])
+        expected = DataFrame([[1, 3, 5]] + [[10, 11, 12]] * n, columns=["a", "b", "c"])
+        tm.assert_frame_equal(df, expected)
+
     @pytest.mark.parametrize("indexer", [tm.setitem, tm.iloc])
-    @pytest.mark.parametrize("box", [Series, np.array, list])
+    @pytest.mark.parametrize("box", [Series, np.array, list, pd.array])
     @pytest.mark.parametrize("n", [1, 2, 3])
-    def test_setitem_broadcasting_rhs_mixed_dtypes(self, n, box, indexer):
+    def test_setitem_slice_broadcasting_rhs_mixed_dtypes(self, n, box, indexer):
         # GH#40440
-        # TODO: Add pandas array as box after GH#40933 is fixed
         df = DataFrame(
             [[1, 3, 5], ["x", "y", "z"]] + [[2, 4, 6]] * n, columns=["a", "b", "c"]
         )

pandas/tests/indexing/test_iloc.py

@@ -122,7 +122,11 @@ def test_iloc_setitem_ea_inplace(self, frame_or_series, box, using_array_manager
         else:
             values = obj[0].values
 
-        obj.iloc[:2] = box(arr[2:])
+        if frame_or_series is Series:
+            obj.iloc[:2] = box(arr[2:])
+        else:
+            obj.iloc[:2, 0] = box(arr[2:])
+
         expected = frame_or_series(np.array([3, 4, 3, 4], dtype="i8"))
         tm.assert_equal(obj, expected)