Hello,

Your ValidateModelMixin and ManagerMixin look perfectly reasonable. You wanted 
to customize two aspects of Django's behavior. You managed to do so in four 
lines and three lines respectively. (I'm leaving out `id_generator` which is 
another concern.)

Preventing database writes without model validation would require further 
changes. You'd have to disable `update`, `bulk_update`, `raw` and perhaps 
others. Even then it would still be possible to use `django.db.connection` to 
make arbitrary queries, etc.

What I'm saying here is — I'm not sure there's a useful line that Django can 
draw and that would work for most projects. I wouldn't use the same constraints 
if I was selling theater tickets or managing access control for health records.

Generally speaking, developers write code that makes (hopefully correct) 
changes to the database. Each team devises best practices to guarantee a 
suitable level of quality. Models and managers mixins are a good technique for 
that.

Best regards,

-- 
Aymeric.



> On 5 Jan 2019, at 22:14, ⁨אורי⁩ <⁨u...@speedy.net⁩> wrote:
> 
> Hi,
> 
> I added this new ticket today and I would like to know what is your feedback 
> or comments?
> 
> https://code.djangoproject.com/ticket/30080 
> <https://code.djangoproject.com/ticket/30080>
> 
> We are using Django for Speedy Net and Speedy Match 
> <https://github.com/speedy-net/speedy-net> (currently Django 1.11.18, we 
> can't upgrade to a newer version of Django because of one of our 
> requirements, django-modeltranslation). I want to validate each model before 
> saving it to the database, so I'm using class ValidateModelMixin as the base 
> of each model.
> 
> For this reason, I want to disable bulk_create in all managers in all of our 
> models. So I added this code:
> 
> class ValidateModelMixin(object):
>     def save(self, *args, **kwargs):
>         """Call `full_clean` before saving."""
>         self.full_clean()
>         return super().save(*args, **kwargs)
> 
> 
> class ManagerMixin(object):
>     def bulk_create(self, *args, **kwargs):
>         raise NotImplementedError("bulk_create is not implemented.")
> 
> 
> class BaseModel(ValidateModelMixin, models.Model):
>     def save(self, *args, **kwargs):
>         try:
>             field = self._meta.get_field('id')
>             if ((not (self.id)) and (hasattr(field, 'id_generator'))):
>                 self.id = field.id_generator()
>                 while (self._meta.model.objects.filter(id=self.id).exists()):
>                     self.id = field.id_generator()
>         except FieldDoesNotExist:
>             pass
>         return super().save(*args, **kwargs)
> 
>     class Meta:
>         abstract = True
> 
> 
> class TimeStampedModel(BaseModel):
>     date_created = models.DateTimeField(auto_now_add=True, db_index=True)
>     date_updated = models.DateTimeField(auto_now=True, db_index=True)
> 
>     class Meta:
>         abstract = True
> 
> 
> class BaseManager(ManagerMixin, models.Manager):
>     pass
> 
> 
> class BaseUserManager(ManagerMixin, DjangoBaseUserManager):
>     pass
> 
> 
> I thought maybe it's good to add these settings - disable bulk_create in all 
> managers and call self.full_clean() before saving the models - as an optional 
> settings both in the project and also in each model (maybe in class Meta) so 
> it will be possible to override Django's default both per-project and also 
> for any specific model. I understand that the default is not to call 
> self.full_clean() before saving the models and to allow bulk_create in the 
> managers, but I suspect this may lead to invalid data in the database of the 
> projects.
> 
> The current code in the master is on 
> https://github.com/speedy-net/speedy-net/blob/master/speedy/core/base/models.py
>  
> <https://github.com/speedy-net/speedy-net/blob/master/speedy/core/base/models.py>,
>  and the code in the branch I'm currently working on is on 
> https://github.com/speedy-net/speedy-net/blob/uri_merge_with_master_2019-01-05_a/speedy/core/base/models.py
>  
> <https://github.com/speedy-net/speedy-net/blob/uri_merge_with_master_2019-01-05_a/speedy/core/base/models.py>.
> 
> Thanks,
> אורי (Uri)
> u...@speedy.net <mailto:u...@speedy.net>
> 
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