Fixed #26320 -- Deprecated implicit OneToOnField parent_link.

django/db/models/options.py

@@ -255,6 +255,11 @@ class Options(object):
                     field = already_created[0]
                 field.primary_key = True
                 self.setup_pk(field)
+                if not field.remote_field.parent_link:
+                    warnings.warn(
+                        'Add parent_link=True to %s as an implicit link is '
+                        'deprecated.' % field, RemovedInDjango20Warning
+                    )
             else:
                 auto = AutoField(verbose_name='ID', primary_key=True, auto_created=True)
                 model.add_to_class('id', auto)

docs/internals/deprecation.txt

@@ -160,6 +160,9 @@ details on these changes.
 
 * The ``django.contrib.gis.utils.precision_wkt()`` function will be removed.
 
+* In multi-table inheritance, implicit promotion of a ``OneToOneField`` to a
+  ``parent_link`` will be removed.
+
 .. _deprecation-removed-in-1.10:
 
 1.10

docs/releases/1.10.txt

@@ -980,6 +980,9 @@ Miscellaneous
   favor of class-based views :class:`~django.views.i18n.JavaScriptCatalog`
   and :class:`~django.views.i18n.JSONCatalog`.
 
+* In multi-table inheritance, implicit promotion of a ``OneToOneField`` to a
+  ``parent_link`` is deprecated. Add ``parent_link=True`` to such fields.
+
 .. _removed-features-1.10:
 
 Features removed in 1.10

tests/invalid_models_tests/test_models.py

@@ -2,6 +2,7 @@
 from __future__ import unicode_literals
 
 import unittest
+import warnings
 
 from django.conf import settings
 from django.core.checks import Error
@@ -739,3 +740,24 @@ class OtherModelTests(SimpleTestCase):
             )
         ]
         self.assertEqual(errors, expected)
+
+    def test_missing_parent_link(self):
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.simplefilter('always')
+
+            class Place(models.Model):
+                pass
+
+            class ParkingLot(Place):
+                # In lieu of any other connector, an existing OneToOneField will be
+                # promoted to the primary key.
+                parent = models.OneToOneField(Place, models.CASCADE)
+
+        self.assertEqual(len(warns), 1)
+        msg = str(warns[0].message)
+        self.assertEqual(
+            msg,
+            'Add parent_link=True to invalid_models_tests.ParkingLot.parent '
+            'as an implicit link is deprecated.'
+        )
+        self.assertEqual(ParkingLot._meta.pk.name, 'parent')

tests/migrations/test_operations.py

@@ -123,6 +123,7 @@ class OperationTestBase(MigrationTestBase):
                         'Pony',
                         models.CASCADE,
                         auto_created=True,
+                        parent_link=True,
                         primary_key=True,
                         to_field='id',
                         serialize=False,

tests/model_inheritance_regress/models.py

@@ -45,12 +45,6 @@ class ParkingLot(Place):
         return "%s the parking lot" % self.name
 
 
-class ParkingLot2(Place):
-    # In lieu of any other connector, an existing OneToOneField will be
-    # promoted to the primary key.
-    parent = models.OneToOneField(Place, models.CASCADE)
-
-
 class ParkingLot3(Place):
     # The parent_link connector need not be the pk on the model.
     primary_key = models.AutoField(primary_key=True)

tests/model_inheritance_regress/tests.py

@@ -13,10 +13,9 @@ from django.test import TestCase
 from .models import (
     ArticleWithAuthor, BachelorParty, BirthdayParty, BusStation, Child,
     DerivedM, InternalCertificationAudit, ItalianRestaurant, M2MChild,
-    MessyBachelorParty, ParkingLot, ParkingLot2, ParkingLot3, ParkingLot4A,
-    ParkingLot4B, Person, Place, Profile, QualityControl, Restaurant,
-    SelfRefChild, SelfRefParent, Senator, Supplier, TrainStation, User,
-    Wholesaler,
+    MessyBachelorParty, ParkingLot, ParkingLot3, ParkingLot4A, ParkingLot4B,
+    Person, Place, Profile, QualityControl, Restaurant, SelfRefChild,
+    SelfRefParent, Senator, Supplier, TrainStation, User, Wholesaler,
 )
 
 
@@ -293,20 +292,11 @@ class ModelInheritanceTest(TestCase):
 
     def test_use_explicit_o2o_to_parent_as_pk(self):
         """
-        Regression tests for #10406
-        If there's a one-to-one link between a child model and the parent and
-        no explicit pk declared, we can use the one-to-one link as the pk on
-        the child.
+        The connector from child to parent need not be the pk on the child.
         """
-        self.assertEqual(ParkingLot2._meta.pk.name, "parent")
-
-        # However, the connector from child to parent need not be the pk on
-        # the child at all.
         self.assertEqual(ParkingLot3._meta.pk.name, "primary_key")
         # the child->parent link
-        self.assertEqual(
-            ParkingLot3._meta.get_ancestor_link(Place).name,
-            "parent")
+        self.assertEqual(ParkingLot3._meta.get_ancestor_link(Place).name, "parent")
 
     def test_use_explicit_o2o_to_parent_from_abstract_model(self):
         self.assertEqual(ParkingLot4A._meta.pk.name, "parent")

tests/serializers/models/data.py

@@ -301,7 +301,7 @@ class InheritBaseModel(BaseModel):
 
 
 class ExplicitInheritBaseModel(BaseModel):
-    parent = models.OneToOneField(BaseModel, models.CASCADE)
+    parent = models.OneToOneField(BaseModel, models.CASCADE, parent_link=True)
     child_data = models.IntegerField()