Ticket #10811: 10811.patch

django/db/models/fields/related.py

@@ -331 +331 @@
                 if not router.allow_relation(value, instance):
                     raise ValueError('Cannot assign "%r": the current database router prevents this relation.' % value)
 
+            pk = tuple(getattr(value, field.attname, None) for _, field in self.field.related_fields)
+            if None in pk and self.field.null is False:
+                raise ValueError('Cannot assign "%r": "%s" instance isn\'t saved in the database.' %
+                                    (value, self.field.rel.to._meta.object_name))
+
         # If we're setting the value of a OneToOneField to None, we need to clear
         # out the cache on any old related object. Otherwise, deleting the
         # previously-related object will also cause this object to be deleted,
@@ -352 +357 @@
 
         # Set the value of the related field
         for lh_field, rh_field in self.field.related_fields:
-            try:
-                setattr(instance, lh_field.attname, getattr(value, rh_field.attname))
-            except AttributeError:
-                setattr(instance, lh_field.attname, None)
+            setattr(instance, lh_field.attname, getattr(value, rh_field.attname, None))
 
         # Since we already know what the related object is, seed the related
         # object caches now, too. This avoids another db hit if you get the

tests/model_regress/tests.py

@@ -6 +6 @@
 import unittest
 
 from django.core.exceptions import ValidationError
-from django.test import TestCase, skipUnlessDBFeature
-from django.utils import six
-from django.utils import tzinfo
 from django.db import connection, router
 from django.db.models.sql import InsertQuery
+from django.test import TestCase, skipUnlessDBFeature
+from django.utils import six, tzinfo
 
 from .models import (Worker, Article, Party, Event, Department,
     BrokenUnicodeMethod, NonAutoPK, Model1, Model2, Model3)
@@ -214 +213 @@
         m3 = Model3.objects.get(model2=1000)
         m3.model2
 
+    def test_assign_unsaved_instance_to_fk(self):
+        """
+        Regression for #10811: Can't assign an unsaved instance to a FK
+        """
+        w = Worker(name="Joe")
+        d = Department(name="Accounting")       # not saved in the database
+        with six.assertRaisesRegex(self, ValueError,
+                'Cannot assign "<Department: Accounting>": '
+                '"Department" instance isn\'t saved in the database.'):
+            w.department = d
+
 
 class ModelValidationTest(TestCase):
     def test_pk_validation(self):