#25148: Add a warning for `CASCADE`ing foreign keys on custom User models.
-------------------------------+--------------------------------------
Reporter: fcurella | Owner: nobody
Type: Uncategorized | Status: new
Component: contrib.auth | Version: 1.8
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by fcurella):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> Assume a custom user models is created as such:
>
> {{{
> class Taco(models.Model):
> flavor = models.CharField(max_length=64, unique=True)
>
> class User(AbstractBaseUser):
> USERNAME_FIELD = 'username'
>
> username = models.CharField(max_length=64, unique=True)
> favorite_taco = models.ForeignKey(Taco, null=True)
> }}}
>
> When deleting the related objects, the user will also be deleted because
> is cascading:
>
> {{{
> taco = Taco.objects.create(flavor="vegetarian")
> user = User.objects.create_user(
> username='taco fan',
> favorite_taco=taco
> )
> User.objects.count() # 1
> taco.delete()
> User.objects.count() # 0
> }}}
>
> This is intended behavior, but it's still pretty dangerous and a common
> trap for beginners.
>
> I'd like to leverage the system check framework to add a Warning whenever
> a FK with `on_delete=CASCADE` is added to a User model. Something along
> the lines of:
>
> {{{
> class AbstractUser():
> @classmethod
> def check(cls, **kwargs):
> errors = super(AbstractUser, cls).check(**kwargs)
> for field in cls._meta.fields:
> if isinstance(field, models.ForeignKey):
> if field.rel.on_delete == models.CASCADE:
> errors.append(checks.Warning(
> "Field {0} is set to CASCADE on delete. You might
> lose users".format(field.name),
> hint="Explicitly set {0}.on_delete to something
> else than `models.CASCADE".format(field.name),
> obj=field,
> id="{0}.W001".format(cls._meta.app_label)
> ))
> return errors
> }}}
New description:
Assume a custom user models is created as such:
{{{
class Taco(models.Model):
flavor = models.CharField(max_length=64, unique=True)
class User(AbstractBaseUser):
USERNAME_FIELD = 'username'
username = models.CharField(max_length=64, unique=True)
favorite_taco = models.ForeignKey(Taco, null=True)
}}}
When deleting the related object, the user will also be deleted because of
cascading:
{{{
taco = Taco.objects.create(flavor="vegetarian")
user = User.objects.create_user(
username='taco fan',
favorite_taco=taco
)
User.objects.count() # 1
taco.delete()
User.objects.count() # 0
}}}
This is intended behavior, but it's still pretty dangerous and a common
trap for beginners.
I'd like to leverage the system check framework to add a Warning whenever
a FK with `on_delete=CASCADE` is added to a User model. Something along
the lines of:
{{{
class AbstractUser():
@classmethod
def check(cls, **kwargs):
errors = super(AbstractUser, cls).check(**kwargs)
for field in cls._meta.fields:
if isinstance(field, models.ForeignKey):
if field.rel.on_delete == models.CASCADE:
errors.append(checks.Warning(
"Field {0} is set to CASCADE on delete. You might
lose users".format(field.name),
hint="Explicitly set {0}.on_delete to something
else than `models.CASCADE".format(field.name),
obj=field,
id="{0}.W001".format(cls._meta.app_label)
))
return errors
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/25148#comment:1>
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