Cache not invalidated for query using Case annotation for ManyToManyF…

…ield

cachalot/tests/test_case_annotation_bug.py

@@ -0,0 +1,42 @@
+from django.contrib.auth.models import Permission
+from django.db.models import Case, When, BooleanField
+from django.test import TransactionTestCase
+
+from cachalot.tests.models import TestChild
+from cachalot.api import invalidate
+
+
+class TestAnnotationFilteringBug(TransactionTestCase):
+    databases = ["default"]
+    def get_child_permissions(self, child):
+        # Dumb query which returns all Permission objects in a ManyToMany relationship
+        perms = child.permissions.all().values_list("pk", flat=True)
+        return Permission.objects.annotate(
+            is_related=Case(When(pk__in=perms, then=True), default=False,
+                            output_field=BooleanField())
+        ).filter(is_related=True)
+
+    def test_result_is_incorrectly_cached(self):
+        child = TestChild.objects.create()
+        permission_A, permission_B = Permission.objects.all()[:2]
+        child.permissions.add(permission_A)
+        self.assertEqual(len(self.get_child_permissions(child)), 1)
+        self.assertSequenceEqual(self.get_child_permissions(child), [permission_A])
+        child.permissions.add(permission_B)
+        self.assertEqual(len(self.get_child_permissions(child)), 2)  # Fails
+        self.assertSequenceEqual(
+            self.get_child_permissions(child), [permission_A, permission_B]
+        )
+
+    def test_result_is_correct_if_cache_cleared(self):
+        child = TestChild.objects.create()
+        permission_A, permission_B = Permission.objects.all()[:2]
+        child.permissions.add(permission_A)
+        self.assertEqual(len(self.get_child_permissions(child)), 1)
+        self.assertSequenceEqual(self.get_child_permissions(child), [permission_A])
+        child.permissions.add(permission_B)
+        invalidate(db_alias="default")
+        self.assertEqual(len(self.get_child_permissions(child)), 2)  # Passes
+        self.assertSequenceEqual(
+            self.get_child_permissions(child), [permission_A, permission_B]
+        )