fixup impl errors

Author: TrevorBergeron

bigframes/core/groupby/dataframe_group_by.py

@@ -748,22 +748,22 @@ def _apply_window_op(
         window_spec = window or window_specs.cumulative_rows(
             grouping_keys=tuple(self._by_col_ids)
         )
-        columns, _ = self._aggregated_columns(numeric_only=numeric_only)
+        columns, labels = self._aggregated_columns(numeric_only=numeric_only)
         block, result_ids = self._block.multi_apply_window_op(
             columns,
             op,
             window_spec=window_spec,
         )
-        block = self._block.project_exprs(
+        block = block.project_exprs(
             tuple(
                 bigframes.operations.where_op.as_expr(
-                    bigframes.operations.notnull_op.as_expr(og_col),
                     r_col,
+                    bigframes.operations.notnull_op.as_expr(og_col),
                     ex.const(None),
                 )
                 for og_col, r_col in zip(columns, result_ids)
             ),
-            labels=block.column_labels,
+            labels=labels,
             drop=True,
         )
 

bigframes/core/groupby/series_group_by.py

@@ -440,10 +440,10 @@ def _apply_window_op(
             window_spec=window_spec,
         )
         if op.skips_nulls:
-            block, result_id = self._block.project_expr(
+            block, result_id = block.project_expr(
                 bigframes.operations.where_op.as_expr(
-                    bigframes.operations.notnull_op.as_expr(self._value_column),
                     result_id,
+                    bigframes.operations.notnull_op.as_expr(self._value_column),
                     ex.const(None),
                 ),
                 label,

bigframes/dataframe.py

@@ -4160,16 +4160,16 @@ def _apply_window_op(
             window_spec=window_spec,
         )
         if op.skips_nulls:
-            block = self._block.project_exprs(
+            block = block.project_exprs(
                 tuple(
                     bigframes.operations.where_op.as_expr(
-                        bigframes.operations.notnull_op.as_expr(og_col),
                         r_col,
+                        bigframes.operations.notnull_op.as_expr(og_col),
                         ex.const(None),
                     )
                     for og_col, r_col in zip(self._block.value_columns, result_ids)
                 ),
-                labels=block.column_labels,
+                labels=self._block.column_labels,
                 drop=True,
             )
         else: