#14082: modelform_factory should use the form's metaclass
-------------------------------------+-------------------------------------
Reporter: jspiros | Owner: Honza_Kral
Status: reopened | Milestone:
Component: Forms | Version: SVN
Resolution: | Keywords: ModelForm,
Triage Stage: Accepted | ModelFormMetaclass,
Needs documentation: 0 | modelform_factory
Patch needs improvement: 0 | Has patch: 1
| Needs tests: 1
-------------------------------------+-------------------------------------
Changes (by melinath):
* cc: melinath (added)
* status: closed => reopened
* resolution: worksforme =>
Comment:
I've looked into this issue and there actually is a problem here.
Essentially, the !ModelFormMetaclass will be run twice.
Suppose I define the following modelform subclass:
{{{
#!python
class MyModelFormMetaclass(ModelFormMetaclass):
run = 0
def __new__(*args, **kwargs):
return ModelFormMetaclass.__new__(*args, **kwargs)
class MyModelForm(ModelForm):
__metaclass__ = MyModelFormMetaclass
}}}
If I use modelform_factory in its current state, the following calls
occur:
1. a call to !ModelFormMetaclass.!__new!__
2. a super() call by !ModelFormMetaclass ![1]
3. a call to !MyModelFormMetaclass.!__new!__ in the course of the super
call. This is how type works, apparently.
4. a call to !ModelFormMetaclass.!__new!__ during
!MyModelFormMetaclass.!__new!__
This should be corrected not only because it's inelegant to be calling
!ModelFormMetaclass.!__new!__ twice and not only because it's odd that the
code currently doesn't call the form's actual metaclass on principle, but
also because this can cause real issues.
Just to pick an example, if I try to modify the base_fields of the form in
my custom metaclass *after* calling !ModelFormMetaclass myself, my changes
will be overridden by !ModelFormMetaclass once the stack gets back up to
it.
![1]
http://code.djangoproject.com/browser/django/trunk/django/forms/models.py#L194
--
Ticket URL: <http://code.djangoproject.com/ticket/14082#comment:6>
Django <http://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 post to this group, send email to django-updates@googlegroups.com.
To unsubscribe from this group, send email to
django-updates+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/django-updates?hl=en.
