Hello Gert, that seems a bit surprising to me and was likely not a desired change.
Could you bisect the exact commit that caused the regression[0]? That would certainly help determining the action to take here. Thanks, Simon [0] https://docs.djangoproject.com/en/3.1/internals/contributing/triaging-tickets/#bisecting-a-regression Le mardi 4 août 2020 à 08:10:00 UTC-4, gertb...@gmail.com a écrit : > (initially posted to > https://forum.djangoproject.com/t/fk-field-caching-behavior-change-between-1-11-x-and-2-x/3151 > > on 26 June but this mailing list might be more appropriate) > > Hi > > Whilst upgrading a codebase from 1.11.x to 2.0/2.2 I noticed a weird > change in behavior of FK fields when copying model instances. > > At the bottom of the post there is a testcase that succeeds on 1.11.x and > fails on 2.x > I think the commit that changed the behavior is > bfb746f983aa741afa3709794e70f1e0ab6040b5 > > So my question is two fold: > > 1. Is the behavior in >=2.0 correct? It seems quite unexpected. > 2. What is the recommended way to clone a model instance? To date we > have been using copy() in a similar fashion to the test without issue. > deepcopy seems to work fine in >=2.0 but we haven’t done too much > testing yet. > > Test (placed in tests/model_fields/test_field_caching_change.py): > > ---------------------code-------------------------- > > import copy > from django.test import TestCase > > from .models import Bar, Foo > > > class ForeignKeyCachingBehaviorTest(TestCase): > def test_copy(self): > foo1 = Foo.objects.create(a='foo1', d=1) > foo2 = Foo.objects.create(a='foo2', d=2) > bar1 = Bar.objects.create(a=foo1, b='bar1') > > bar2 = copy.copy(bar1) > > bar2.pk = None > bar2.a = foo2 > > # bar2 points to foo2 > self.assertEqual(bar2.a, foo2) > self.assertEqual(bar2.a.id, bar2.a_id) > > # bar1 is unchanged and must still point to foo1 > # These fail on Django >= 2.0 > self.assertEqual(bar1.a, foo1) > self.assertEqual(bar1.a.id, bar1.a_id) > > ---------------------code-------------------------- > > and executed that via: > > python3.6 tests/runtests.py --parallel 1 model_fields > > Regards > Gert Burger > -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/c284e35e-ae02-44e5-b44d-4994eff9b248n%40googlegroups.com.
