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
19691	Inconsistency in instantiating/validating ModelForms:  CharFields vs. with ImageField only.	pfeiffersimon@…	nobody	"Hi I found a sligth inconsistency in the instantiation/validation of the different field types. Its kinda hard to describe so here some code:

Consider the following models:
{{{
class Text(models.Model):
    """"""Just a basic model to store some text""""""
    create_date = models.DateTimeField(auto_now_add=True)
    content = models.TextField()


class Picture(models.Model):
    """"""Just a basic model to store a picture""""""    
    create_date = models.DateTimeField(auto_now_add=True)
    picture=models.ImageField(upload_to=""pics"")

}}}

And the following forms:


{{{
from django.forms import ModelForm
from notebook.models import *

class TextForm(ModelForm):
    class Meta:
        model=Text
        
class PictureForm(ModelForm):
    class Meta:
        model=Picture
}}}

When you now instantiate PictureForm and a TextForm with a bound instance, but empty request.POST / request.FILES likes this:


{{{
#get_or_none() returns a valid model instance in both cases below
#req.POST and req.FILES are both empty QueryDict instances

form_text = TextForm(req.POST,instance=get_or_none(Text,pk=primary_key))
form_pic = PictureForm(req.POST,req.FILES ,instance=get_or_none(Picture,pk=primary_key))

#The validation of form_text 
form_text.is_valid() 
# >>> FALSE
form_pic.is_valid()
# >>> True
}}}

So basically, the PictureForm ignores that it gets handed an empty req.FILES & req.POST and just uses the instance that is bound.

Whereas, the TextModel throws errors which get rendered although it has a bound a instance:

{{{
# found with pdb
>>> form_text.is_valid() 
FALSE
>>>form_text.initial
{'content': u'Some content from the database', 'id': 15}

}}}

So as you can see its just a little inconsistency. I do not even know I should have reported it. If you are wondering how I came about doing something like that:


{{{
# Compact way of writing a create/edit form
def picture_edit(req,primary_keyk=None):
    
    form = PictureForm(req.POST,req.FILES ,instance=get_or_none(Picture,pk=primary_key))
    # Works for         ^^^^^^^^^^^^^^^^req.POST={} & req.FILES={}  and instance == Model()                             
  
    if req.method == 'POST': 
        if form.is_valid():
            form.save()
            return redirect(""notebook_dashboard"")
    
    return render(req, 'notebook/picture_edit.html', {'form': form, })

def text_edit(req,pk=None):
    
    form = TextForm(req.POST,instance=get_or_none(Text,pk=pk))
    # this does not   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  when req.POST={} and instance == Model()
    if req.method == 'POST': # If the form has been submitted...
        if form.is_valid():
            form.save()
            return redirect(""notebook_dashboard"") #Redirect to dash
            #Optional else clause not explicitly used
    import pdb; pdb.set_trace()
    return render(req, 'notebook/text_edit.html', {'form': form, })


}}}"	Cleanup/optimization	closed	Forms	1.4	Normal	invalid			Unreviewed	0	0	0	0	0	0