save_new_objects in ModelFromsets do not handle intitial data

[Johannes Maron]

If you create a ModelFormSet and pass initial data for some forms, the forms are evaluated as has_changed False.
All in all that is true, but it has the the side effect that the forms in the formset don't get saved, tho they contain data.

The error is here:
​https://github.com/django/django/blob/master/django/forms/models.py#L777-L778

It should not only be checked for has_changed but also for initial data.

[Tim Graham]

You should use initial forms instead of extra forms if you require those populated forms to be submitted. Changing the behavior to validate and save unchanged extra forms would be backwards incompatible. Feel free to reopen if I missed something.

[Johannes Maron]

That does not work for ModelFormSets as the pop initial to initial_extra and only except existing objects using the Queryset.
There currently is no way to create objects using a ModelFormSet with initial data.

I get your point, about compatibility, but you should decide if this odd behavior is a bug or a feature. Personally it feels like a bug. Especially as Model and regular form sets handle initial data so differently. There is no consistent behavior nor any documentation about this.

[Tim Graham]

I had no trouble with this view:

from django.forms.models import modelformset_factory

def test_view(request):
    qs = Poll.objects.none()
    PollFormSet = modelformset_factory(Poll, fields='__all__')
    if request.method == 'POST':
        formset = PollFormSet(request.POST, queryset=qs)
        if formset.is_valid():
            formset.save()
    else:
        formset = PollFormSet(queryset=qs, initial=[
            {'question': 'initial', 'pub_date': timezone.now()}])
    return render(request, 'polls/manage.html', {'formset': formset})

Can you provide a snippet that demonstrates your problem?

[Johannes Maron]

As I said:
It does not work if your submitted are not yet created and you can't pass a queryset.

from django.forms.models import modelformset_factory

def test_view(request):
    qs = Poll.objects.none()
    PollFormSet = modelformset_factory(Poll, fields='__all__')
    if request.method == 'POST':
        formset = PollFormSet(request.POST, initial=[{'question': 'Foo'}, {'question': 'Bar'}])
        if formset.is_valid():
            obj_list = formset.save()
            assert len(obj_list) == 2
    else:
        formset = PollFormSet(queryset=qs, initial=[
            {'question': 'initial', 'pub_date': timezone.now()}])
    return render(request, 'polls/manage.html', {'formset': formset})

This will fail.