Demonstrate bug where related_name is not working properly when using…

manage.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+import os
+import sys
+
+
+def main():
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "test_settings")
+
+    try:
+        from django.core.management import execute_from_command_line
+    except ImportError as exc:
+        raise ImportError(
+            "Couldn't import Django. Are you sure it's installed and "
+            "available on your PYTHONPATH environment variable? Did you "
+            "forget to activate a virtual environment?"
+        ) from exc
+
+    execute_from_command_line(sys.argv)
+
+
+if __name__ == "__main__":
+    main()

second_testapp/migrations/0001_initial.py

@@ -0,0 +1,40 @@
+# Generated by Django 4.2.2 on 2023-06-20 07:54
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('testapp', '0003_product_order'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='BaseReview',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('type', models.CharField(choices=[('second_testapp.orderreview', 'order review')], db_index=True, max_length=255)),
+                ('rating', models.IntegerField()),
+                ('order', models.OneToOneField(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='order_review', to='testapp.order')),
+                ('product', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='reviews', to='testapp.product')),
+            ],
+            options={
+                'abstract': False,
+            },
+        ),
+        migrations.CreateModel(
+            name='OrderReview',
+            fields=[
+            ],
+            options={
+                'proxy': True,
+                'indexes': [],
+                'constraints': [],
+            },
+            bases=('second_testapp.basereview',),
+        ),
+    ]

second_testapp/models.py

@@ -0,0 +1,12 @@
+from django.db import models
+
+from typedmodels.models import TypedModel
+
+
+class BaseReview(TypedModel):
+    rating = models.IntegerField()
+
+
+class OrderReview(BaseReview):
+    product = models.ForeignKey("testapp.Product", on_delete=models.CASCADE, related_name="reviews", null=True)
+    order = models.OneToOneField("testapp.Order", on_delete=models.CASCADE, related_name="order_review", null=True)

test_settings.py

@@ -1,6 +1,7 @@
 INSTALLED_APPS = (
     "typedmodels",
     "django.contrib.contenttypes",
+    "second_testapp",  # purposefully before testapp to test related models with lazy loading
     "testapp",
 )
 MIDDLEWARE_CLASSES = ()

testapp/migrations/0003_product_order.py

@@ -0,0 +1,29 @@
+# Generated by Django 4.2.2 on 2023-06-20 07:53
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('testapp', '0002_developer_employee_manager'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Product',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(default='Product name', max_length=255)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='Order',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('external_id', models.CharField(default='123', max_length=255)),
+                ('product', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='orders', to='testapp.product')),
+            ],
+        ),
+    ]

testapp/models.py

@@ -134,3 +134,12 @@ class Developer(Employee):
 class Manager(Employee):
     # Adds the _exact_ same field as Developer. Shouldn't error.
     name = models.CharField(max_length=255, null=True)
+
+
+class Product(models.Model):
+    name = models.CharField(max_length=255, default="Product name")
+
+
+class Order(models.Model):
+    external_id = models.CharField(max_length=255, default="123")
+    product = models.ForeignKey(Product, on_delete=models.CASCADE, related_name="orders")

typedmodels/models.py

@@ -1,13 +1,12 @@
-import inspect
 from functools import partial
-import types
 
 from django.core.exceptions import FieldDoesNotExist, FieldError
 from django.core.serializers.python import Serializer as _PythonSerializer
 from django.core.serializers.xml_serializer import Serializer as _XmlSerializer
 from django.db import models
 from django.db.models.base import ModelBase, DEFERRED
 from django.db.models.fields import Field
+from django.db.models.fields.related import RelatedField
 from django.db.models.options import make_immutable_fields_list
 from django.utils.encoding import smart_str
 
@@ -95,21 +94,12 @@ class Meta:
                         )
                     )
 
-                if isinstance(field, models.fields.related.RelatedField):
+                if isinstance(field, RelatedField):
                     # Monkey patching field instance to make do_related_class use created class instead of base_class.
                     # Actually that class doesn't exist yet, so we just monkey patch base_class for a while,
                     # changing _meta.model_name, so accessor names are generated properly.
                     # We'll do more stuff when the class is created.
-                    old_do_related_class = field.do_related_class
-
-                    def do_related_class(self, other, cls):
-                        base_class_name = base_class.__name__
-                        cls._meta.model_name = classname.lower()
-                        old_do_related_class(other, cls)
-                        cls._meta.model_name = base_class_name.lower()
-
-                    field.do_related_class = types.MethodType(do_related_class, field)
-                if isinstance(field, models.fields.related.RelatedField):
+                    field.do_related_class = _get_related_class_function(base_class, classname, field)
                     remote_field = field.remote_field
                     if (
                         isinstance(remote_field.model, TypedModel)
@@ -453,6 +443,24 @@ def _get_unique_checks(self, exclude=None, **kwargs):
         return unique_checks, date_checks
 
 
+def _get_related_class_function(base_class, classname, field):
+    """
+    Returns a function that can be used to replace a RelatedField's
+    do_related_class method. This function is used to monkey patch
+    RelatedFields on subclasses of TypedModel to use the created class
+    instead of the base class.
+    """
+    old_do_related_class = field.do_related_class
+
+    def do_related_class(self, other, cls):
+        base_class_name = base_class.__name__
+        cls._meta.model_name = classname.lower()
+        old_do_related_class(other, cls)
+        cls._meta.model_name = base_class_name.lower()
+
+    return partial(do_related_class, field)
+
+
 # Monkey patching Python and XML serializers in Django to use model name from base class.
 # This should be preferably done by changing __unicode__ method for ._meta attribute in each model,
 # but it doesn’t work.

typedmodels/tests.py

@@ -3,6 +3,8 @@
 
 import pytest
 
+from second_testapp.models import OrderReview
+
 try:
     import yaml
 
@@ -28,6 +30,8 @@
     UniqueIdentifier,
     Child2,
     Employee,
+    Product,
+    Order,
 )
 
 
@@ -444,3 +448,24 @@ class Tester2(Employee):
 
         class Tester3(Employee):
             name = models.IntegerField(null=True)
+
+
+def test_related_name_is_preserved_for_foreign_keys(db):
+    """Regression test for the following scenario:
+    A subclass of a typed model has foreign key to two models in a different app, while they are also related
+    to each other.
+    """
+    product = Product.objects.create(name="test")
+    order = Order.objects.create(product=product)
+
+    order_review = OrderReview.objects.create(
+        order=order,
+        product=product,
+        rating=5,
+    )
+    assert order_review.order == order
+    assert order_review.product == product
+
+    assert order.order_review == order_review
+    assert product.reviews.first() == order_review
+