ModelMultipleChoiceField + show_hidden_initial + has_changed = TypeError

[dibrovsd@…]

hi

def test(request):
    u""" for debug and test's """

    from django import forms
    from django.http import HttpResponse
    from django.template import RequestContext, Template

    user = models.User.objects.get(pk=1)
    changed = None

    class TestForm(forms.Form):
        users = forms.ModelMultipleChoiceField(show_hidden_initial=True, queryset=models.User.objects.all())

    if request.method == 'POST':
        form = TestForm(data=request.POST)
        form.is_valid()

        ### next line raised: TypeError int() argument must be a string or a number, not 'list' ###
        ### django/db/models/fields/__init__.py in get_prep_value, line 613 ###
        changed = form.has_changed() 
    else:
        form = TestForm(initial={'users': [user]})
    
    c = RequestContext(request, {'form': form, 'changed': changed})
    
    t = Template("""
        <form method=POST>
            {% csrf_token %}
            {{form}}
            <input type=submit>
        </form>

        {{changed}}
        """) 

    return HttpResponse(t.render(c))

if change to:
users = forms.ModelMultipleChoiceField(queryset=models.User.objects.all())
and
form = TestForm(data=request.POST, initial={'users': [user]})

This works, but may lead to loss of the changes made by other users

[Claude Paroz]

I'll investigate...

[Aymeric Augustin]

Can you provide a full traceback please? If you're seeing Django's error debug page, there's a button to show a copy-pasteable backtrace. Please add it in a comment.

[Claude Paroz]

The base issue is that ModelMultipleChoiceField has currently no to_python method. Previously (1.5), has_changed did not call to_python on values coming from hidden initial widgets, so this issue remained unnoticed. Hence, this is also a regression.

[anonymous]

Replying to aaugustin:

Can you provide a full traceback please? If you're seeing Django's error debug page, there's a button to show a copy-pasteable backtrace. Please add it in a comment.

traceback still needed?

[Claude Paroz]

Generally, traceback is appreciated, yes. But now that we have a patch to fix the issue, it's not useful any more. Please check if the following patch solves your issue.

​https://github.com/django/django/pull/2040

[dibrovsd@…]

It works. Thank you!

[Claude Paroz <claude@…>]

In 8a9c8bb90736451e6bdea82723cbb23a695146fb:

Fixed #21568 -- Added missing ModelMultipleChoiceField to_python method

Thanks dibrovsd at gmail.com for the report and Simon Charette
for the review.

[Claude Paroz <claude@…>]

In 34c4b93c84e86665d66d0b31da8e30fd581d5b5f:

[1.6.x] Fixed #21568 -- Added missing ModelMultipleChoiceField to_python method

Thanks dibrovsd at gmail.com for the report and Simon Charette
for the review.
Backport of 8a9c8bb90 from master.