Opened 9 years ago
Closed 9 years ago
#25148 closed Uncategorized (duplicate)
Add a warning for `CASCADE`ing foreign keys on custom User models.
Reported by: | Flavio Curella | Owned by: | Flavio Curella |
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Component: | contrib.auth | Version: | 1.8 |
Severity: | Normal | Keywords: | |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
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
Change History (5)
comment:1 by , 9 years ago
Description: | modified (diff) |
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comment:2 by , 9 years ago
Owner: | changed from | to
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Status: | new → assigned |
comment:3 by , 9 years ago
comment:5 by , 9 years ago
Resolution: | → duplicate |
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Status: | assigned → closed |
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A better use of your time may be to fix #21127 -- changing the default of
on_delete
. At that point, I don't think such a check would be needed.