Fixed #27629 -- Added router.allow_relation() calls for assignments between unsaved model instances.

1 files changed, 6 insertions, 8 deletions

diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index f9b770fade..850ea99fa1 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/django/db/models/fields/related_descriptors.py
@@ -205,11 +205,10 @@ class ForwardManyToOneDescriptor:
         elif value is not None:
             if instance._state.db is None:
                 instance._state.db = router.db_for_write(instance.__class__, instance=value)
-            elif value._state.db is None:
+            if value._state.db is None:
                 value._state.db = router.db_for_write(value.__class__, instance=instance)
-            elif value._state.db is not None and instance._state.db is not None:
-                if not router.allow_relation(value, instance):
-                    raise ValueError('Cannot assign "%r": the current database router prevents this relation.' % value)
+            if not router.allow_relation(value, instance):
+                raise ValueError('Cannot assign "%r": the current database router prevents this relation.' % value)
 
         remote_field = self.field.remote_field
         # If we're setting the value of a OneToOneField to None, we need to clear
@@ -451,11 +450,10 @@ class ReverseOneToOneDescriptor:
         else:
             if instance._state.db is None:
                 instance._state.db = router.db_for_write(instance.__class__, instance=value)
-            elif value._state.db is None:
+            if value._state.db is None:
                 value._state.db = router.db_for_write(value.__class__, instance=instance)
-            elif value._state.db is not None and instance._state.db is not None:
-                if not router.allow_relation(value, instance):
-                    raise ValueError('Cannot assign "%r": the current database router prevents this relation.' % value)
+            if not router.allow_relation(value, instance):
+                raise ValueError('Cannot assign "%r": the current database router prevents this relation.' % value)
 
             related_pk = tuple(getattr(instance, field.attname) for field in self.related.field.foreign_related_fields)
             # Set the value of the related field to the value of the related object's related field