Fixed #36404 -- Fixed Aggregate.filter using OuterRef.

Regression in a76035e925ff4e6d8676c65cb135c74b993b1039.
Thank you to Simon Charette for the review.

co-authored-by: Simon Charette <charette.s@gmail.com>

django/db/models/aggregates.py

@@ -95,7 +95,7 @@ class Aggregate(Func):
             raise TypeError(f"{self.__class__.__name__} does not allow default.")
 
         self.distinct = distinct
-        self.filter = filter and AggregateFilter(filter)
+        self.filter = None if filter is None else AggregateFilter(filter)
         self.default = default
         self.order_by = AggregateOrderBy.from_param(
             f"{self.__class__.__name__}.order_by", order_by
@@ -120,11 +120,6 @@ class Aggregate(Func):
     ):
         # Aggregates are not allowed in UPDATE queries, so ignore for_save
         c = super().resolve_expression(query, allow_joins, reuse, summarize)
-        c.filter = (
-            c.filter.resolve_expression(query, allow_joins, reuse, summarize)
-            if c.filter
-            else None
-        )
         c.order_by = (
             c.order_by.resolve_expression(query, allow_joins, reuse, summarize)
             if c.order_by

docs/releases/5.2.2.txt

@@ -22,3 +22,6 @@ Bugfixes
 * Fixed a regression in Django 5.2 where subclasses of ``RemoteUserMiddleware``
   that had overridden ``process_request()`` were no longer supported
   (:ticket:`36390`).
+
+* Fixed a regression in Django 5.2 that caused a crash when using ``OuterRef``
+  in the ``filter`` argument of an ``Aggregate`` expression (:ticket:`36404`).

tests/aggregation/test_filter_argument.py

@@ -84,6 +84,10 @@ class FilteredAggregateTests(TestCase):
                     Author.objects.aggregate(age=agg)["age"], expected_result
                 )
 
+    def test_empty_filtered_aggregates(self):
+        agg = Count("pk", filter=Q())
+        self.assertEqual(Author.objects.aggregate(count=agg)["count"], 3)
+
     def test_double_filtered_aggregates(self):
         agg = Sum("age", filter=Q(Q(name="test2") & ~Q(name="test")))
         self.assertEqual(Author.objects.aggregate(age=agg)["age"], 60)
@@ -182,6 +186,23 @@ class FilteredAggregateTests(TestCase):
         )
         self.assertEqual(aggregate, {"max_rating": 4.5})
 
+    def test_filtered_aggregrate_ref_in_subquery_annotation(self):
+        aggs = (
+            Author.objects.annotate(
+                count=Subquery(
+                    Book.objects.annotate(
+                        weird_count=Count(
+                            "pk",
+                            filter=Q(pages=OuterRef("age")),
+                        )
+                    ).values("weird_count")[:1]
+                ),
+            )
+            .order_by("pk")
+            .aggregate(sum=Sum("count"))
+        )
+        self.assertEqual(aggs["sum"], 0)
+
     def test_filtered_aggregate_on_exists(self):
         aggregate = Book.objects.values("publisher").aggregate(
             max_rating=Max(