#26633: OneToOneField's non-existence behaviour is inelegant
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Reporter: skorokithakis | Owner: nobody
Type: Uncategorized | Status: new
Component: Database layer (models, ORM) | Version: 1.9
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Currently, if you have a model A with a nullable OneToOneField `b_field`
to model B, and try to do:
{{{
a = A.objects.all()[0] # Get a random object.
a.b_field
RelatedObjectDoesNotExist: Number has no allocation.
}}}
It is very inelegant to raise an exception in such a frequent use case as
this, and doubly so when returning `None` is completely unambiguous. It
makes writing elegant functional code very hard, as you have to break out
of the string of functions to check whether this raised an exception.
Right now, if you want to check that the object's relation exists, you can
do `hasattr(a, "b_field")`, which is rather unclean and, from what I
understand, only works because hasattr swallows the exception, which is
not the case in Python 3.2+.
I propose that the lookup has a try/except block internally and catches
the `RelatedObjectDoesNotExist` exception there, returning `None`. I don't
believe there will be any negative side-effects from this change, but code
that expects an exception to be raised will need to be changed...
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Ticket URL: <https://code.djangoproject.com/ticket/26633>
Django <https://code.djangoproject.com/>
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