Ticket #17615: 17615.diff

django/db/models/base.py

@@ -719 +719 @@
 
             # Exclude the current object from the query if we are editing an
             # instance (as opposed to creating a new one)
-            if not self._state.adding and self.pk is not None:
-                qs = qs.exclude(pk=self.pk)
-
+            # Note that we need to use the pk as defined by model_class, not
+            # self.pk. These can be different fields because model inheritance
+            # allows single model to have effectively multiple primary keys.
+            # Refs #17615.
+            model_class_pk = self._get_pk_val(model_class._meta)
+            if not self._state.adding and model_class_pk is not None:
+                qs = qs.exclude(pk=model_class_pk)
             if qs.exists():
                 if len(unique_check) == 1:
                     key = unique_check[0]

tests/regressiontests/model_inheritance_regress/models.py

@@ -163 +163 @@
 
 class TrainStation(Station):
     zone = models.IntegerField()
+
+class User(models.Model):
+    username = models.CharField(max_length=30, unique=True)
+
+class Profile(User):
+    profile_id = models.AutoField(primary_key=True)
+    extra = models.CharField(max_length=30, blank=True)

tests/regressiontests/model_inheritance_regress/tests.py

@@ -6 +6 @@
 
 import datetime
 from operator import attrgetter
+from django import forms
 
 from django.test import TestCase
 
@@ -13 +14 @@
     ParkingLot2, ParkingLot3, Supplier, Wholesaler, Child, SelfRefParent,
     SelfRefChild, ArticleWithAuthor, M2MChild, QualityControl, DerivedM,
     Person, BirthdayParty, BachelorParty, MessyBachelorParty,
-    InternalCertificationAudit, BusStation, TrainStation)
+    InternalCertificationAudit, BusStation, TrainStation, User, Profile)
+
+
+class ProfileForm(forms.ModelForm):
+    class Meta:
+        model = Profile
 
 
 class ModelInheritanceTest(TestCase):
@@ -408 +414 @@
         )
         self.assertIs(BusStation._meta.pk.model, BusStation)
         self.assertIs(TrainStation._meta.pk.model, TrainStation)
+
+    def test_inherited_unique_field_with_form(self):
+        User.objects.create(username="user_only")
+        p = Profile.objects.create(username="user_with_profile")
+        form = ProfileForm({'username': "user_with_profile", 'extra': "hello"}, instance=p)
+        self.assertTrue(form.is_valid())