On Wed, Feb 9, 2011 at 1:43 AM, Stephen Burrows
<stephen.r.burr...@gmail.com> wrote:
> Hi! I was going to submit this as a ticket, but I glanced over the patch
> submission guidelines once more and this seems to fall under the category of
> a "non-trivial change" that would require a design decision. The code
> samples/tracebacks can be viewed nicely formatted on github. [1]
> Assume the following models in `app`:
> from django.db import models
>
> class Orange(models.Model):
> pass
>
> class BaseClass(models.Model):
> field = models.ForeignKey(Orange)
> class Meta:
> abstract = True
>
> class Parent1(BaseClass):
> class Meta:
> abstract=True
>
> class Parent2(BaseClass):
> class Meta:
> abstract=True
>
> class Child(Parent1, Parent2):
> pass
> Currently, this definition will raise the following errors during model
> validation:
>
> Unhandled exception in thread started by <bound method Command.inner_run of
> <django.core.management.commands.runserver.Command object at 0x101470490>>
> Traceback (most recent call last):
> File "..../django/core/management/commands/runserver.py", line 88, in
> inner_run
> self.validate(display_num_errors=True)
> File "..../django/core/management/base.py", line 253, in validate
> raise CommandError("One or more models did not validate:\n%s" %
> error_text)
> django.core.management.base.CommandError: One or more models did not
> validate:
> app.child: Accessor for field 'field' clashes with related field
> 'Orange.child_set'. Add a related_name argument to the definition for
> 'field'.
> app.child: Accessor for field 'field' clashes with related field
> 'Orange.child_set'. Add a related_name argument to the definition for
> 'field'.
> Using the %(app_label)s_%(class)s_related syntax only makes things worse:
>
> Unhandled exception in thread started by <bound method Command.inner_run of
> <django.core.management.commands.runserver.Command object at 0x10146e4d0>>
> Traceback (most recent call last):
> File "..../django/core/management/commands/runserver.py", line 88, in
> inner_run
> self.validate(display_num_errors=True)
> File "..../django/core/management/base.py", line 253, in validate
> raise CommandError("One or more models did not validate:\n%s" %
> error_text)
> django.core.management.base.CommandError: One or more models did not
> validate:
> app.child: Accessor for field 'field' clashes with related field
> 'Orange.app_child_related'. Add a related_name argument to the definition
> for 'field'.
> app.child: Reverse query name for field 'field' clashes with related field
> 'Orange.app_child_related'. Add a related_name argument to the definition
> for 'field'.
> app.child: Accessor for field 'field' clashes with related field
> 'Orange.app_child_related'. Add a related_name argument to the definition
> for 'field'.
> app.child: Reverse query name for field 'field' clashes with related field
> 'Orange.app_child_related'. Add a related_name argument to the definition
> for 'field'.
>
> Instead of causing errors, it seems like the field should only be inherited
> once from BaseClass.
I don't think this is very controversial at all -- I can't see any
reason why BaseClass.field should be represented twice in Child's
field list.
> My patch [1] handles this as follows: On each field
> instance, track the class it was originally declared for and the first
> non-abstract class that it shows up in. Then, when a field is being added to
> a class, check to make sure that it only gets added if it isn't a
> "duplicate". (The patch would incidentally also need to move the
> get_FIELD_display method declaration [2] into cls._meta.add_field.) If this
> is an acceptable idea, I would be happy to add tests and docs. If the
> general idea is acceptable, but the implementation is flawed, I would be
> happy to write patches using other methods that people may suggest; this was
> just what made sense to me.
Thanks for the patch; if you want to make sure this isn't forgotten,
please open a ticket and attach your patch there.
While you're in the ticket system, you might also want to take a look
at #14705. I haven't checked myself to be sure, but it's possible that
that patch might address this problem -- at the very least, it's
somewhat related.
Yours,
Russ Magee %-)
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