[4.1.x] Fixed #33898 -- Fixed Window() expression crash with ArrayAgg().

Thanks Kia for the report.

Regression in e06dc4571e.
Backport of fd93db97c7 from main

django/db/models/expressions.py

@@ -1669,7 +1669,7 @@ class Window(SQLiteNumericMixin, Expression):
         if not connection.features.supports_over_clause:
             raise NotSupportedError("This backend does not support window expressions.")
         expr_sql, params = compiler.compile(self.source_expression)
-        window_sql, window_params = [], []
+        window_sql, window_params = [], ()
 
         if self.partition_by is not None:
             sql_expr, sql_params = self.partition_by.as_sql(
@@ -1678,24 +1678,23 @@ class Window(SQLiteNumericMixin, Expression):
                 template="PARTITION BY %(expressions)s",
             )
             window_sql.append(sql_expr)
-            window_params.extend(sql_params)
+            window_params += tuple(sql_params)
 
         if self.order_by is not None:
             order_sql, order_params = compiler.compile(self.order_by)
             window_sql.append(order_sql)
-            window_params.extend(order_params)
+            window_params += tuple(order_params)
 
         if self.frame:
             frame_sql, frame_params = compiler.compile(self.frame)
             window_sql.append(frame_sql)
-            window_params.extend(frame_params)
+            window_params += tuple(frame_params)
 
-        params.extend(window_params)
         template = template or self.template
 
         return (
             template % {"expression": expr_sql, "window": " ".join(window_sql).strip()},
-            params,
+            (*params, *window_params),
         )
 
     def as_sqlite(self, compiler, connection):

docs/releases/4.1.1.txt

@@ -22,3 +22,7 @@ Bugfixes
 * Fixed a regression in Django 4.1 that caused an incorrect redirection to the
   admin changelist view when using *"Save and continue editing"* and *"Save and
   add another"* options (:ticket:`33893`).
+
+* Fixed a regression in Django 4.1 that caused a crash of
+  :class:`~django.db.models.expressions.Window` expressions with
+  :class:`~django.contrib.postgres.aggregates.ArrayAgg` (:ticket:`33898`).

tests/postgres_tests/test_aggregates.py

@@ -8,6 +8,7 @@ from django.db.models import (
     Q,
     Subquery,
     Value,
+    Window,
 )
 from django.db.models.fields.json import KeyTextTransform, KeyTransform
 from django.db.models.functions import Cast, Concat, Substr
@@ -669,6 +670,22 @@ class TestGeneralAggregate(PostgreSQLTestCase):
             inner_qs.values_list("integer_field", flat=True),
         )
 
+    def test_window(self):
+        self.assertCountEqual(
+            AggregateTestModel.objects.annotate(
+                integers=Window(
+                    expression=ArrayAgg("char_field"),
+                    partition_by=F("integer_field"),
+                )
+            ).values("integers", "char_field"),
+            [
+                {"integers": ["Foo1", "Foo3"], "char_field": "Foo1"},
+                {"integers": ["Foo1", "Foo3"], "char_field": "Foo3"},
+                {"integers": ["Foo2"], "char_field": "Foo2"},
+                {"integers": ["Foo4"], "char_field": "Foo4"},
+            ],
+        )
+
 
 class TestAggregateDistinct(PostgreSQLTestCase):
     @classmethod