A bit more coverage and better error messages

python/cudf/cudf/core/column_accessor.py

@@ -373,12 +373,16 @@ def get_labels_by_index(self, index: Any) -> tuple:
             return self.names[start:stop:step]
         elif pd.api.types.is_integer(index):
             return (self.names[index],)
-        elif index and all(map(is_bool, index)):
-            if len(index) != len(self.names):
-                raise IndexError("Invalid boolean mask for column selection")
+        elif (bn := len(index)) > 0 and all(map(is_bool, index)):
+            if bn != (n := len(self.names)):
+                raise IndexError(
+                    f"Boolean mask has wrong length: {bn} not {n}"
+                )
             if isinstance(index, (pd.Series, cudf.Series)):
                 # Don't allow iloc indexing with series
-                raise IndexError("Cannot use Series object for iloc indexing")
+                raise NotImplementedError(
+                    "Cannot use Series object for mask iloc indexing"
+                )
             # TODO: Doesn't handle on-device columns
             return tuple(n for n, keep in zip(self.names, index) if keep)
         else:
@@ -476,7 +480,11 @@ def _select_by_label_list_like(self, key: Any) -> ColumnAccessor:
         # Might be a generator
         key = tuple(key)
         # Special-casing for boolean mask
-        if key and all(map(is_bool, key)):
+        if (bn := len(key)) > 0 and all(map(is_bool, key)):
+            if bn != (n := len(self.names)):
+                raise IndexError(
+                    f"Boolean mask has wrong length: {bn} not {n}"
+                )
             data = dict(
                 item
                 for item, keep in zip(self._grouped_data.items(), key)

python/cudf/cudf/core/indexed_frame.py

@@ -2905,7 +2905,7 @@ def _apply_boolean_mask(self, boolean_mask):
         if not is_bool_dtype(boolean_mask.dtype):
             raise ValueError("boolean_mask is not boolean type.")
         if (bn := len(boolean_mask)) != (n := len(self)):
-            raise IndexError(f"Boolean index has wrong length: {bn} not {n}")
+            raise IndexError(f"Boolean mask has wrong length: {bn} not {n}")
         return self._from_columns_like_self(
             libcudf.stream_compaction.apply_boolean_mask(
                 list(self._index._columns + self._columns), boolean_mask

python/cudf/cudf/core/single_column_frame.py

@@ -405,7 +405,7 @@ def _get_elements_from_column(self, arg) -> Union[ScalarLike, ColumnBase]:
             if is_bool_dtype(arg.dtype):
                 if (bn := len(arg)) != (n := len(self)):
                     raise IndexError(
-                        f"Boolean index has wrong length: {bn} not {n}"
+                        f"Boolean mask has wrong length: {bn} not {n}"
                     )
                 return self._column.apply_boolean_mask(arg)
             raise NotImplementedError(f"Unknown indexer {type(arg)}")

python/cudf/cudf/tests/test_indexing.py

@@ -1708,8 +1708,36 @@ def test_boolean_mask_wrong_length(indexer, mask):
 def test_boolean_mask_columns(indexer):
     df = pd.DataFrame(np.zeros((3, 3)))
     cdf = cudf.from_pandas(df)
-
-    expect = getattr(df, indexer)[:, [True, False, True]]
-    got = getattr(cdf, indexer)[:, [True, False, True]]
+    mask = [True, False, True]
+    expect = getattr(df, indexer)[:, mask]
+    got = getattr(cdf, indexer)[:, mask]
 
     assert_eq(expect, got)
+
+
+@pytest.mark.parametrize("indexer", ["loc", "iloc"])
+@pytest.mark.parametrize(
+    "mask",
+    [[False, True], [False, False, True, True, True]],
+    ids=["too-short", "too-long"],
+)
+def test_boolean_mask_columns_wrong_length(indexer, mask):
+    df = pd.DataFrame(np.zeros((3, 3)))
+    cdf = cudf.from_pandas(df)
+
+    with pytest.raises(IndexError):
+        getattr(df, indexer)[:, mask]
+    with pytest.raises(IndexError):
+        getattr(cdf, indexer)[:, mask]
+
+
+def test_boolean_mask_columns_iloc_series():
+    df = pd.DataFrame(np.zeros((3, 3)))
+    cdf = cudf.from_pandas(df)
+
+    mask = pd.Series([True, False, True], dtype=bool)
+    with pytest.raises(NotImplementedError):
+        df.iloc[:, mask]
+
+    with pytest.raises(NotImplementedError):
+        cdf.iloc[:, mask]