fix Subquery annotation detection in dnfs() for Django 6.0+

cacheops/tree.py

@@ -159,9 +159,14 @@ def table_for(alias):
 
     # Add any subqueries used for annotation
     if qs.query.annotations:
-        subqueries = (query_dnf(getattr(q, 'query', None))
-                      for q in qs.query.annotations.values() if isinstance(q, Subquery))
-        dnfs_.update(join_with(lcat, subqueries))
+        sub_dnfs = []
+        for q in qs.query.annotations.values():
+            if isinstance(q, Subquery):
+                sub_dnfs.append(query_dnf(getattr(q, 'query', None)))
+            elif isinstance(q, Query):
+                sub_dnfs.append(query_dnf(q))
+        if sub_dnfs:
+            dnfs_.update(join_with(lcat, sub_dnfs))
 
     return dnfs_
 

tests/tests.py

@@ -643,6 +643,30 @@ def test_365(self):
         categories = Category.objects.cache().annotate(newest_post=Subquery(newest_post[:1]))
         self.assertEqual(categories[0].newest_post, post.pk)
 
+    def test_366(self):
+        """
+        Check that dnfs() detects table dependencies from
+        Subquery annotations.
+
+        Django 6.0+ resolves Subquery into raw Query objects
+        in qs.query.annotations, so this verifies detection
+        works regardless of how the annotation is stored.
+        """
+        from cacheops.tree import dnfs
+
+        newest_post = Post.objects.filter(
+            category=OuterRef('pk')
+        ).order_by('-pk').values('pk')
+        qs = Category.objects.cache().annotate(
+            newest_post=Subquery(newest_post[:1])
+        )
+        result = dnfs(qs)
+
+        self.assertEqual(result, {
+            Category._meta.db_table: [{}],
+            Post._meta.db_table: [{}],
+        })
+
     @unittest.skipIf(platform.python_implementation() == "PyPy", "dill doesn't do that in PyPy")
     def test_385(self):
         Client.objects.create(name='Client Name')