Try bisecting to find the commit in Django where the behavior changed:
https://docs.djangoproject.com/en/dev/internals/contributing/triaging-tickets/#bisecting-a-regression
On Saturday, October 29, 2016 at 9:57:53 AM UTC-4, in...@lucasvandijk.nl
wrote:
>
> Hi all,
>
> I have a simple model whichs acts as custom many-to-many association table
> with additional data.
>
> ```
> class NetworkLinkAssociation(models.Model):
> """
> We use our own many-to-many association table, because we want to keep
> track which links are added, and which links are deleted/disabled in
> comparison to the parent network.
> """
>
> network = models.ForeignKey('Network', related_name='links_assoc',
> on_delete=models.CASCADE)
> link = models.ForeignKey('Link', related_name='networks_assoc',
> on_delete=models.CASCADE)
>
> type = enum.EnumField(AssociationType,
> default=AssociationType.UNCHANGED,
> null=True)
>
> class Meta:
> unique_together = ('network', 'link')
>
> @property
> def link_disabled(self):
> return self.type == AssociationType.REMOVED
> ```
>
> When trying to simply create a new object django raises an error:
>
> ```
> link_assoc = NetworkLinkAssociation()
> link_assoc.link = link
> link_assoc.network = network
> link_assoc.save()
> ```
>
> "ValueError: Cannot force an update in save() with no primary key.".
>
> I'm 100% sure the `link` and `network` objects exist, so what else could
> the problem be? This used to work fine Django 1.9.
>
> Possibly related bug on Github:
> https://github.com/jpwatts/django-positions/issues/49
>
> Thanks in advance,
> Lucas
>
>
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