Fixed #29172 -- Fixed crash with Window expression in a subquery.

django/db/models/expressions.py

@@ -315,8 +315,10 @@ class BaseExpression:
 
     def relabeled_clone(self, change_map):
         clone = self.copy()
-        clone.set_source_expressions(
-            [e.relabeled_clone(change_map) for e in self.get_source_expressions()])
+        clone.set_source_expressions([
+            e.relabeled_clone(change_map) if e is not None else None
+            for e in self.get_source_expressions()
+        ])
         return clone
 
     def copy(self):

docs/releases/2.0.3.txt

@@ -25,3 +25,6 @@ Bugfixes
 
 * Fixed a regression where a ``When()`` expression with a list argument crashes
   (:ticket:`29166`).
+
+* Fixed crash when using a ``Window()`` expression in a subquery
+  (:ticket:`29172`).

tests/expressions_window/tests.py

@@ -650,6 +650,19 @@ class WindowFunctionTests(TestCase):
                 salary=Window(expression=Sum(Value(10000), order_by=F('pk').asc())),
             )
 
+    def test_window_expression_within_subquery(self):
+        subquery_qs = Employee.objects.annotate(
+            highest=Window(FirstValue('id'), partition_by=F('department'), order_by=F('salary').desc())
+        ).values('highest')
+        highest_salary = Employee.objects.filter(pk__in=subquery_qs)
+        self.assertSequenceEqual(highest_salary.values('department', 'salary'), [
+            {'department': 'Accounting', 'salary': 50000},
+            {'department': 'Sales', 'salary': 55000},
+            {'department': 'Marketing', 'salary': 40000},
+            {'department': 'IT', 'salary': 60000},
+            {'department': 'Management', 'salary': 100000}
+        ])
+
     def test_invalid_start_value_range(self):
         msg = "start argument must be a negative integer, zero, or None, but got '3'."
         with self.assertRaisesMessage(ValueError, msg):