#18480: Inherited model fails to handle blank field properly
-------------------------------------+-------------------------------------
Reporter: yuval_a | Owner: navi7
Type: Bug | Status: assigned
Component: Database layer | Version: 1.4
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 0 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Comment (by navi7):
This is a kind of red herring.
The actual problem stems from the model coming up with the same field name
as name of the derived class itself so it can have the reference to the
base class. Model building then just overwrites our field. The simplest
test is this:
{{{
#!python
class FruitFly(models.Model):
pass
class CroatianFruitFly(FruitFly):
croatianfruitfly = models.IntegerField()
fly2 = CroatianFruitFly() # this throws wrong exception
}}}
The error thrown is:
{{{
#!python
ValueError: Cannot assign None: "CroatianFruitFly.croatianfruitfly" does
not allow null values.
}}}
And that's totally misleading.
As I'm totally new to Django, I don't know a way out of it. It seems that
using the same field name as the class can be explicitly forbidden by
throwing meaningful errors when the model is built. Then again, that could
potentially be a breaking change.
Or, the name of the reference could be mangled somehow to not use that
exact name.
Anyways, I need someone who knows the internals a bit more to look at
this.
--
Ticket URL: <https://code.djangoproject.com/ticket/18480#comment:6>
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