ModelMultipleChoiceField does not check all data types properly

Demo of django ticket 22808

https://code.djangoproject.com/ticket/22808

1. models.py

from django.db import models


class Color(models.Model):
    name = models.CharField(max_length=255)

    def __unicode__(self):
        return self.name


class Shirt(models.Model):
    name = models.CharField(max_length=255)
    colors = models.ManyToManyField(Color)

    def __unicode__(self):
        return self.name

2. forms.py

from django import forms

from .models import Shirt


class ShirtForm(forms.ModelForm):
    class Meta:
        model = Shirt

3. urls.py

from django.conf.urls import patterns, include, url

from . import views

urlpatterns = patterns('',
    url(r'^$', views.test),
)

4. views.py

from django.shortcuts import render

from django.http import HttpResponse

from .forms import ShirtForm


def test(request):
    def run_form(data):
        form = ShirtForm(data)
        if form.is_valid():
            print 'success'
        else:
            print dict(form.errors)

    # color id is integer (and 1 exists in database)
    run_form({'name': 'foo', 'colors': [1,]})
    # result: success

    # color id is of type string
    run_form({'name': 'foo', 'colors': ['asdf',]})
    # result: {'colors': [u'"asdf" is not a valid value for a primary key.']}

    # color id is of type list
    run_form({'name': 'foo', 'colors': [['asdf'],]})
    # expected result: {'colors': [u'["asdf"] is not a valid value for a primary key.']}
    # actual result: TypeError: int() argument must be a string or a number, not 'list'

    # color id is of type dict
    run_form({'name': 'foo', 'colors': [{'asdf': 'qwer'},]})
    # expected result: {'colors': [u'{"asdf": "qwer"} is not a valid value for a primary key.']}
    # actual result: TypeError: int() argument must be a string or a number, not 'dict'

    return HttpResponse('buzzbomb')

5. full stack trace

Traceback (most recent call last):
  File "/usr/lib/python2.7/wsgiref/handlers.py", line 85, in run
    self.result = application(self.environ, self.start_response)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/contrib/staticfiles/handlers.py", line 67, in __call__
    return self.application(environ, start_response)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/core/handlers/wsgi.py", line 206, in __call__
    response = self.get_response(request)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 194, in get_response
    response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/mattiasll01/code/tests/model_multiple_choice_field_check_type/mmcfct/stuff/views.py", line 26, in test
    run_form({'name': 'foo', 'colors': [['asdf'],]})
  File "/home/mattiasll01/code/tests/model_multiple_choice_field_check_type/mmcfct/stuff/views.py", line 12, in run_form
    if form.is_valid():
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/forms/forms.py", line 129, in is_valid
    return self.is_bound and not bool(self.errors)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/forms/forms.py", line 121, in errors
    self.full_clean()
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/forms/forms.py", line 273, in full_clean
    self._clean_fields()
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/forms/forms.py", line 288, in _clean_fields
    value = field.clean(value)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/forms/models.py", line 1186, in clean
    self.queryset.filter(**{key: pk})
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/query.py", line 593, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/query.py", line 611, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1204, in add_q
    clause = self._add_q(where_part, used_aliases)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1240, in _add_q
    current_negated=current_negated)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1131, in build_filter
    clause.add(constraint, AND)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/utils/tree.py", line 104, in add
    data = self._prepare_data(data)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/sql/where.py", line 79, in _prepare_data
    value = obj.prepare(lookup_type, value)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/sql/where.py", line 352, in prepare
    return self.field.get_prep_lookup(lookup_type, value)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 369, in get_prep_lookup
    return self.get_prep_value(value)
  File "/home/mattiasll01/.virtualenvs/test/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 613, in get_prep_value
    return int(value)
TypeError: int() argument must be a string or a number, not 'list'