Fix invalidate_m2o for polymorphic models (#430)

* Fix `invalidate_m2o` for polymorphic models

* Fix `invalidate_m2o` for polymorphic models

Co-authored-by: Andrey Alekseev <andrey.alekseev@satitasa.com>

Author: aletor123

cacheops/query.py

@@ -529,8 +529,13 @@ def invalidate_m2o(sender, instance, using=DEFAULT_DB_ALIAS):
     """Invoke invalidation for m2o and m2m queries to a deleted instance"""
     all_fields = sender._meta.get_fields(include_hidden=True, include_parents=True)
     m2o_fields = [f for f in all_fields if isinstance(f, models.ManyToOneRel)]
+    fk_fields_names_map = {
+        f.name: f.attname
+        for f in all_fields if isinstance(f, models.ForeignKey)
+    }
     for f in m2o_fields:
-        value = getattr(instance, f.field_name)
+        attr = fk_fields_names_map.get(f.field_name, f.field_name)
+        value = getattr(instance, attr)
         rmodel, rfield = f.related_model, f.remote_field.attname
         invalidate_dict(rmodel, {rfield: value}, using=using)
 

tests/models.py

@@ -151,14 +151,34 @@ class Meta:
         proxy = True
 
 
+class MediaType(models.Model):
+    name = models.CharField(max_length=50)
+
 # Multi-table inheritance
 class Media(models.Model):
     name = models.CharField(max_length=128)
+    media_type = models.ForeignKey(
+        MediaType,
+        on_delete=models.CASCADE,
+    )
+
+    def __str__(self):
+        return str(self.media_type)
+
 
 class Movie(Media):
     year = models.IntegerField()
 
 
+class Scene(models.Model):
+    """Model with FK to submodel."""
+    name = models.CharField(max_length=50)
+    movie = models.ForeignKey(
+        Movie,
+        on_delete=models.CASCADE,
+        related_name="scenes",
+    )
+
 # M2M models
 class Label(models.Model):
     text = models.CharField(max_length=127, blank=True, default='')

tests/tests.py

@@ -14,8 +14,9 @@
 from django.db.models.expressions import RawSQL
 
 from cacheops import invalidate_model, invalidate_obj, \
-                     cached, cached_view, cached_as, cached_view_as
+    cached, cached_view, cached_as, cached_view_as
 from cacheops import invalidate_fragment
+from cacheops.query import invalidate_m2o
 from cacheops.templatetags.cacheops import register
 
 decorator_tag = register.decorator_tag
@@ -681,6 +682,40 @@ def test_407_reverse(self):
         with self.assertNumQueries(1):
             self.assertEqual(len(Brand.objects.filter(labels=1).cache()), 0)
 
+    @mock.patch('cacheops.query.invalidate_dict')
+    def test_430(self, mock_invalidate_dict):
+        media_type = MediaType.objects.create(
+            name="some type"
+        )
+        movie = Movie.objects.create(
+            year=2022,
+            media_type=media_type,
+        )
+        Scene.objects.create(
+            name="first scene",
+            movie=movie,
+        )
+        invalidate_m2o(Movie, movie)
+
+        obj_movie_dict = mock_invalidate_dict.call_args[0][1]
+        self.assertFalse(isinstance(obj_movie_dict['movie_id'], Media))
+        self.assertTrue(isinstance(obj_movie_dict['movie_id'], int))
+
+    def test_430_no_error_raises(self):
+        media_type = MediaType.objects.create(
+            name="some type"
+        )
+        movie = Movie.objects.create(
+            year=2022,
+            media_type=media_type,
+        )
+        Scene.objects.create(
+            name="first scene",
+            movie=movie,
+        )
+        # no error raises on delete
+        media_type.delete()
+
 
 class RelatedTests(BaseTestCase):
     fixtures = ['basic']