Merge pull request #679 from jazzband/test-fk-abstract

Make related polymorphic object manager selection more robust to multiple inheritance scenarios.

Author: bckohan

docs/changelog.rst

@@ -3,6 +3,8 @@ Changelog
 
 v4.3.0 (202X-XX-XX)
 -------------------
+
+* Fixed `Foreign key resolves to parent class when using abstract models <https://github.com/jazzband/django-polymorphic/issues/437>`_
 * Fixed `Support Q expressions that contain subquery expressions <https://github.com/jazzband/django-polymorphic/pull/572>`_
 
 v4.2.0 (2025-12-04)

src/polymorphic/base.py

@@ -60,6 +60,13 @@ def __new__(self, model_name, bases, attrs, **kwargs):
         # create new model
         new_class = self.call_superclass_new_method(model_name, bases, attrs, **kwargs)
 
+        if new_class._meta.base_manager_name is None:
+            # by default, use polymorphic manager as the base manager - i.e. for
+            # related fields etc. This could happen in multi-inheritance scenarios
+            # where one parent is polymorphic and the other not and the non poly parent
+            # is higher in the MRO
+            new_class._meta.base_manager_name = "objects"
+
         # check if the model fields are all allowed
         self.validate_model_fields(new_class)
 

src/polymorphic/tests/migrations/0001_initial.py

@@ -1,4 +1,4 @@
-# Generated by Django 4.2.26 on 2025-12-04 12:57
+# Generated by Django 4.2.26 on 2025-12-05 02:34
 
 from django.db import migrations, models
 import django.db.models.deletion
@@ -256,7 +256,6 @@ class Migration(migrations.Migration):
             ],
             options={
                 'abstract': False,
-                'base_manager_name': 'objects',
             },
             bases=(polymorphic.showfields.ShowFieldTypeAndContent, models.Model),
         ),
@@ -586,7 +585,6 @@ class Migration(migrations.Migration):
             ],
             options={
                 'abstract': False,
-                'base_manager_name': 'objects',
             },
             bases=('tests.relationbase',),
         ),
@@ -598,7 +596,6 @@ class Migration(migrations.Migration):
             ],
             options={
                 'abstract': False,
-                'base_manager_name': 'objects',
             },
             bases=('tests.relationbase',),
         ),
@@ -1060,7 +1057,6 @@ class Migration(migrations.Migration):
             ],
             options={
                 'abstract': False,
-                'base_manager_name': 'objects',
             },
             bases=('tests.relationb',),
         ),

src/polymorphic/tests/models.py

@@ -109,7 +109,12 @@ class Enhance_Inherit(Enhance_Base, Enhance_Plain):
     field_i = models.CharField(max_length=30)
 
 
-class RelationBase(ShowFieldTypeAndContent, PolymorphicModel):
+class RelationAbstractModel(models.Model):
+    class Meta:
+        abstract = True
+
+
+class RelationBase(RelationAbstractModel, ShowFieldTypeAndContent, PolymorphicModel):
     field_base = models.CharField(max_length=30)
     fk = models.ForeignKey(
         "self", on_delete=models.CASCADE, null=True, related_name="relationbase_set"

src/polymorphic/tests/test_orm.py

@@ -696,7 +696,7 @@ def test_relation_base(self):
         oa.m2m.add(oa)
         oa.m2m.add(ob)
 
-        objects = RelationBase.objects.all()
+        objects = RelationBase.objects.order_by("pk").all()
         assert (
             repr(objects[0])
             == '<RelationBase: id 1, field_base (CharField) "base", fk (ForeignKey) None, m2m (ManyToManyField) 0>'