#32597: generic inline formsets: object has no attribute 'fk'
-------------------------------------+-------------------------------------
               Reporter:  etanter    |          Owner:  nobody
                   Type:  Bug        |         Status:  new
              Component:  Forms      |        Version:  2.2
               Severity:  Normal     |       Keywords:  generic field,
           Triage Stage:             |  inline formset
  Unreviewed                         |      Has patch:  0
    Needs documentation:  0          |    Needs tests:  0
Patch needs improvement:  0          |  Easy pickings:  0
                  UI/UX:  0          |
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 Hi,

 I think I'm facing a zombie-bug reminiscent of ticket #9498:
 https://code.djangoproject.com/ticket/9498
 From 12 years ago and marked as solved.


 The setting is simple: I have a model with a generic field (with non-
 standard names). The corresponding inline class declares the `ct_field`
 and `ct_fk_field` as required.

 If I don't try to customize the formset, then all works fine. However, as
 soon as I declare a formset attribute for the inline (even if I use
 `formset=BaseInlineFormSet`), it crashes with an error:

 `type object 'DocumentFormSet' has no attribute 'fk'`

 With the debugger I traced the problem down to the execution of this
 method in BaseInlineFormSet (during the initialization process of the
 formsets):

   {{{#!python
 @classmethod
 def get_default_prefix(cls):
    return
 cls.fk.remote_field.get_accessor_name(model=cls.model).replace('+', '')
   }}}

 Problem is: `cls` has no field `fk` (it has `ct_fk_field` and `ct_field`
 properly set, though).

 In fact, the instance of `BaseInlineFormSet` has a field `fk`, used in
 many instance methods, but the class itself does not :-(

 I've done the following "fix":

 1. redefine the get_default_prefix method to use `ct_field` instead of
 `fk`

   {{{#!python
     @classmethod
     def get_default_prefix(cls):
         return
 cls.ct_field.remote_field.get_accessor_name(model=cls.model).replace('+',
 '')
   }}}


 2. at the instance methods level, I then had the same errors (`no
 attribute 'fk'`), so I defined:

   {{{#!python
     @property
     def fk(self):
         return self.ct_field
 }}}
 And it works (I tried defining an `empty_form` property to set an initial
 value of my inlines, and it behaves as expected.

 Is that a known bug of 2.2? is it fixed upstream? Or am I missing
 something and there's some documentation somewhere explaining what to do
 in that case? (my fix is clearly not intended for users to do, I believe).

 Thanks

 Éric

-- 
Ticket URL: <https://code.djangoproject.com/ticket/32597>
Django <https://code.djangoproject.com/>
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