id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
9362	InlineAdminForm breaks content_type FK on model	Carl Meyer	Carl Meyer	"r8586 fixed ""View on Site"" links for admin inline formsets, by having {{{InlineAdminForm.__init__}}} set a temporary ""content_type_id"" attribute on the inline-edited ""original"" instance to the content type id of its model, and then using that attribute in the template to link to the redirection.

This is all fine and dandy, except when the model being edited inline already has a ""content_type"" field which is a foreign key to !ContentType (most likely because it has a generic foreign key).  In this case, !InlineAdminForm reassigns an already-existing ""content_type_id"" attribute to point to the wrong model entirely, breaking any behavior of the instance that depends on the generic foreign key.

This behavior can be seen with these test models:

{{{
from django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes import generic

class Parent(models.Model):
    name = models.CharField(max_length=50)

    def __unicode__(self):
        return self.name

class Teacher(models.Model):
    name = models.CharField(max_length=50)

    def __unicode__(self):
        return self.name

class Child(models.Model):
    name = models.CharField(max_length=50)
    teacher = models.ForeignKey(Teacher)

    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    parent = generic.GenericForeignKey()

    def __unicode__(self):
        return u'I am %s, a child of %s' % (self.name, self.parent)
}}}

With this admin configuration:

{{{
from django.contrib import admin
from models import Child, Teacher, Parent

class ChildInline(admin.TabularInline):
    model = Child
    extra = 1

class TeacherAdmin(admin.ModelAdmin):
    inlines = (ChildInline,)

admin.site.register(Teacher, TeacherAdmin)
admin.site.register(Parent)
}}}

In the admin, create a Parent named John, then create a Teacher named Sally, then add a Child named Joe using the inline formset for the Teacher.  After saving the Child, where the new Child's __unicode__ representation should be displayed as ""I am Joe, a child of John"", it will instead say ""I am Joe, a child of I am Joe, a child of John"".  This is because InlineAdminForm has changed Joe's content_type_id from Parent to Child, so Joe's ""parent"" attribute is now pointing to himself.

(The reason for the Teacher model and FK in the above examples is to make it clear that this occurs with any ordinary InlineAdmin, not only with a GenericInlineAdmin).

The easy fix is to use a more obscure attribute name for the temporary ""my content type"" attribute needed for redirection.  Technically it would still be possible to mistakenly overwrite an existing attribute, but much less likely than it is now."		closed	contrib.admin	1.0		fixed		Robin Breathe Robert	Accepted	1	0	0	0	0	0