#27629: Inconsistent check of allow_relation in
ForwardManyToOneDescriptor.__set__
-------------------------------------+-------------------------------------
Reporter: Sven | Owner: nobody
Coenye |
Type: Bug | Status: new
Component: Database | Version: 1.10
layer (models, ORM) | Keywords: allow_relation
Severity: Normal | ForwardManyToOneDescriptor
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
The method in django/db/models/fields/related_descriptors.py currently
contains the following code:
{{{
if instance._state.db is None:
instance._state.db = router.db_for_write(instance.__class__,
instance=value)
elif value._state.db is None:
value._state.db = router.db_for_write(value.__class__,
instance=instance)
elif value._state.db is not None and instance._state.db is not None:
if not router.allow_relation(value, instance):
raise ValueError('Cannot assign "%r": the current database router
prevents this relation.' % value)
}}}
When using an application containing the following model
{{{
from otherapp.models import AdProgram
class Order(models.Model):
first_name = models.CharField(max_length = 15)
last_name = models.CharField(max_length = 20)
program = models.ForeignKey(AdProgram, db_constraint=False) #
No cross database FK constraints under MSSQL
}}}
where the imported model belongs to a legacy database different from the
application's own database, the code in question does not flag an
inappropriate relationship. E.g. when submitting a ModelForm containing
these three fields, the value for program will be saved to the
application's database even if allow_relation would return False.
When the model definition is changed to
{{{
from otherapp.models import AdProgram, AdTerm
class Order(models.Model):
first_name = models.CharField(max_length = 15)
last_name = models.CharField(max_length = 20)
program = models.ForeignKey(AdProgram, db_constraint=False) #
No cross database FK constraints under MSSQL
term = models.ForeignKey(AdTerm, db_constraint=False)
}}}
"program" again gets a free pass, but "term" triggers the ValueError
exception.
The reason is that instance._state.db is None for the "program" field but
contains the value retrieved for "program" for any subsequent fields.
I believe those "elif" statements should be plain "if" statements so the
uninitialized value on the first pass does not fall through?
--
Ticket URL: <https://code.djangoproject.com/ticket/27629>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/050.da54449307169e4bb0449e58d9152b37%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
