- Fixed bug in checking the existence of custom __init__ method in an object. The __init__ wasn't called previously.

- Added unit-tests for #615
- update changelog

Co-authored-by: Bartosz Dabrowski <bartosz.dabrowski@adverity.com>
Co-authored-by: Brian Kohan <bckohan@gmail.com>

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 v4.2.0 (2025-12-04)
 -------------------
 
+* Fixed `The objects which were transmogrified aren't initialized correctly if they implement __init__ method. <https://github.com/jazzband/django-polymorphic/issues/615>`_
 * Implemented `Defer to chunk_size parameter on .iterators for fetching get_real_instances() <https://github.com/jazzband/django-polymorphic/pull/672>`_
 * Fixed `Show full admin context (breadcrumb and logout nav) in model type selection admin form <https://github.com/jazzband/django-polymorphic/pull/580>`_
 * Fixed `Issue with Autocomplete Fields in StackedPolymorphicInline.Child Inline <https://github.com/jazzband/django-polymorphic/issues/546>`_

src/polymorphic/query.py

@@ -87,7 +87,7 @@ def transmogrify(cls, obj):
     """
     Upcast a class to a different type without asking questions.
     """
-    if "__init__" not in obj.__dict__:
+    if "__init__" not in obj.__class__.__dict__:
         # Just assign __class__ to a different value.
         new = obj
         new.__class__ = cls

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

@@ -1,4 +1,4 @@
-# Generated by Django 4.2.26 on 2025-12-02 16:47
+# Generated by Django 4.2.26 on 2025-12-03 23:29
 
 from django.db import migrations, models
 import django.db.models.deletion
@@ -12,8 +12,8 @@ class Migration(migrations.Migration):
     initial = True
 
     dependencies = [
-        ('auth', '0012_alter_user_first_name_max_length'),
         ('contenttypes', '0002_remove_content_type_name'),
+        ('auth', '0012_alter_user_first_name_max_length'),
     ]
 
     operations = [
@@ -56,6 +56,18 @@ class Migration(migrations.Migration):
             },
             bases=(polymorphic.showfields.ShowFieldTypeAndContent, models.Model),
         ),
+        migrations.CreateModel(
+            name='Duck',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=30)),
+                ('polymorphic_ctype', models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_%(app_label)s.%(class)s_set+', to='contenttypes.contenttype')),
+            ],
+            options={
+                'abstract': False,
+                'base_manager_name': 'objects',
+            },
+        ),
         migrations.CreateModel(
             name='Enhance_Base',
             fields=[
@@ -315,6 +327,17 @@ class Migration(migrations.Migration):
             },
             bases=('tests.blogbase',),
         ),
+        migrations.CreateModel(
+            name='BlueHeadDuck',
+            fields=[
+                ('duck_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='tests.duck')),
+            ],
+            options={
+                'abstract': False,
+                'base_manager_name': 'objects',
+            },
+            bases=('tests.duck',),
+        ),
         migrations.CreateModel(
             name='CustomPkInherit',
             fields=[
@@ -833,18 +856,6 @@ class Migration(migrations.Migration):
                 'base_manager_name': 'objects',
             },
         ),
-        migrations.CreateModel(
-            name='Duck',
-            fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('name', models.CharField(max_length=30)),
-                ('polymorphic_ctype', models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_%(app_label)s.%(class)s_set+', to='contenttypes.contenttype')),
-            ],
-            options={
-                'abstract': False,
-                'base_manager_name': 'objects',
-            },
-        ),
         migrations.CreateModel(
             name='DateModel',
             fields=[
@@ -1108,6 +1119,17 @@ class Migration(migrations.Migration):
             },
             bases=(polymorphic.showfields.ShowFieldTypeAndContent, models.Model),
         ),
+        migrations.CreateModel(
+            name='PurpleHeadDuck',
+            fields=[
+            ],
+            options={
+                'proxy': True,
+                'indexes': [],
+                'constraints': [],
+            },
+            bases=('tests.blueheadduck', models.Model),
+        ),
         migrations.CreateModel(
             name='Model2D',
             fields=[

src/polymorphic/tests/models.py

@@ -535,3 +535,23 @@ class UserProfile(Participant):
 class Team(models.Model):
     team_name = models.CharField(max_length=100)
     user_profiles = models.ManyToManyField(UserProfile, related_name="user_teams")
+
+
+class BlueHeadDuck(Duck):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.color = "blue"
+
+
+class HomeDuck(models.Model):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.home = "Duckburg"
+
+    class Meta:
+        abstract = True
+
+
+class PurpleHeadDuck(HomeDuck, BlueHeadDuck):
+    class Meta:
+        proxy = True

src/polymorphic/tests/test_orm.py

@@ -23,7 +23,6 @@ from polymorphic.tests.models import (
     ChildModelWithManager,
     CustomPkBase,
     CustomPkInherit,
-    Duck,
     Enhance_Base,
     Enhance_Inherit,
     InitTestModelSubclass,
@@ -90,6 +89,8 @@ from polymorphic.tests.models import (
     UUIDPlainC,
     UUIDProject,
     UUIDResearchProject,
+    Duck,
+    PurpleHeadDuck,
 )
 
 
@@ -1411,3 +1412,13 @@ class PolymorphicTests(TransactionTestCase):
                 # known deletion issue with oracle
                 # https://github.com/jazzband/django-polymorphic/issues/673
                 pass
+
+    def test_transmogrify_with_init(self):
+        pur = PurpleHeadDuck.objects.create()
+        assert pur.color == "blue"
+        assert pur.home == "Duckburg"
+
+        pur = Duck.objects.get(id=pur.id)
+        assert pur.color == "blue"
+        # issues/615 fixes following line:
+        assert pur.home == "Duckburg"