Bug fix: Creating a new object instance causes a DoesNotExist exception

[hellsgate1001]

This prevents a DoesNotExists exception when creating a new instance rather than editing an existing one

[coveralls]

Coverage remained the same when pulling 48a5b0ff298e25ed89587aa7d9ff8323310a93a9 on hellsgate1001:master into 47a3e24c3fa095648a1dc447d778a13f847daa76 on karanlyons:master.

[karanlyons]

Hey @hellsgate1001, I'm not sure I fully understand the bug this solves. Could you add a test showing the behavior it fixes? Also, self.id should be self.pk to support models using custom primary keys. Thanks!

[coveralls]

Coverage remained the same when pulling 252b6f7a3db06d73d1309ae0cb4100560958fe20 on hellsgate1001:master into 47a3e24c3fa095648a1dc447d778a13f847daa76 on karanlyons:master.

[hellsgate1001]

I've made that change. Would you still like a test to be added? I have to be honest and say that I'm not sure how I'd go about adding one so if you have any hints on how I do that I'd be grateful.

[karanlyons]

Test-wise, if you can perhaps just paste some code into this issue that shows what you were doing that broke STC, I can write a proper test for it. I'm still not a huge fan of the self.pk check for previously stated reasons, so if I can get a proper test to see if there's a better way to handle this case, it'd be really awesome. Thanks!

[hellsgate1001]

It seems to be models which have a required foreign key which are tripping the error. It happens in admin with no custom forms. In the following example the error would be seen when attempting to create a new Tag:

class TagCategory(SaveTheChange, models.Model):
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name

    def get_id_and_name(self):
        return [self.id, self.name]

    class Meta:
        verbose_name_plural = 'Tag Categories'
        ordering = ['name']

class Tag(SaveTheChange, models.Model):
    name = models.CharField(max_length=100)
    category = models.ForeignKey(TagCategory, related_name='tag_category_name')

    def __unicode__(self):
        return self.name

    def get_id_and_name(self):
        return [self.id, self.name]

    class Meta:
        ordering = ['category__name','name']

I've tested this with the foreign key being optional and it works correctly in that case.

[karanlyons]

Awesome, thanks for the example Brian! I'll take a closer look at this over the weekend, and roll some fix into the next release.

[bkonkle]

Here's a test that triggers the bug: https://github.com/lincolnloop/django-save-the-change/commit/3add04c135aec4cfc31a6be26b5f7b48d4b6d0e7

I'm playing around with it to see if I can find a more ideal fix.

[karanlyons]

Superceded by #4, thanks again @hellsgate1001 & @bkonkle.