Model instances without primary key value are unhashable in admin panel

I have implemented a “backup” functionality when a user wants to keep a revision of his object along with all the related ones. I have implemented the admin integration and registered all the “follows” correctly. When the user presses the “create new backup” button, then the following code is executed:

    with reversion.create_revision():
        main_object.save()

        reversion.set_user(request.user)
        reversion.set_comment(comment)

and a revision is created for the object and all the related ones.

The problem appears when I create a new object that has a relationship to the main_object. When the new object is created, if the user presses “Create new Backup”, then a revision is successfully created for the main_object and all the related ones BUT the previous revisions show this message on the admin panel: "Model instances without primary key value are unhashable".

The traceback that appears is:

File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  132.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/django/utils/decorators.py" in _wrapped_view
  110.                     response = view_func(request, *args, **kwargs)
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  57.         response = view_func(request, *args, **kwargs)
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/django/contrib/admin/sites.py" in inner
  233.             return view(request, *args, **kwargs)
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/reversion/admin.py" in revision_view
  238.             context,
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/reversion/admin.py" in _reversion_revisionform_view
  184.                 version.revision.revert(delete=True)
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/reversion/models.py" in revert
  89.                         if item not in old_revision:
File "/Users/platico/PycharmProjects/news-service/src/lib/python2.7/site-packages/django/db/models/base.py" in __hash__
  521.             raise TypeError("Model instances without primary key value are unhashable")

with an Exception Type of TypeError and an Exception Value of Model instances without primary key value are unhashable

[etianen]

Cool, I’ll aim for a release sometime next week! Thanks for your help!

On 20 November 2017 at 09:13, Roman Karpovich [e-mail] wrote:

@etianen https://github.com/etianen seems that fix working. thanks alot.

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[roman-karpovich]

Same problem for me. Multi-table inheritance.

import reversion
from django.db import models


@reversion.register(follow=('diaryevent_set', ))
class Diary(models.Model):
    pass


@reversion.register(follow=('specialdiaryevent', ))
class DiaryEvent(models.Model):
    diary = models.ForeignKey(Diary)


@reversion.register(follow=('diaryevent_ptr', ))
class SpecialDiaryEvent(DiaryEvent):
    pass

diary = Diary.objects.create()

with reversion.create_revision():
    reversion.add_to_revision(diary)

SpecialDiaryEvent.objects.create(diary=diary)

with reversion.create_revision():
    reversion.add_to_revision(diary)

reversion.models.Version.objects.get_for_object(diary)[1].revision.revert(delete=True)