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
27993	Impossible to clear an ArrayField with a forms.MultipleChoiceField	Olivier Dormond	heathervm	"While using a {{{forms.MultipleChoiceField}}} to represent an {{{ArrayField}}}, there is no way to clear the {{{ArrayField}}}. Unselecting all items from the rendred {{{<select mutiple=""multiple"">}}} correctly leads to an empty list showing up in the form's {{{cleaned_data}}} but the value is ignored. The problem is that {{{django.forms.models.construct_instance}}} ignores the value due to {{{django.forms.widgets.SelectMultiple}}} (correctly) returning {{{True}}} from {{{value_omitted_from_data(...)}}}.

The following small code example will demonstrate the issue by failing on the last assert.
{{{
from django.db import models
from django import forms
from django.contrib.postgres.fields import ArrayField

class TestModel(models.Model):
    array = ArrayField(models.CharField(max_length=10), default=list, blank=True)
    class Meta:
        app_label = 'test'

class TestForm(forms.ModelForm):
    array = forms.MultipleChoiceField(choices=(('one', 'One'), ('two', 'Two')), required=False)
    class Meta:
        model = TestModel
        fields = '__all__'

test_instance = TestModel(array=['one'])
assert test_instance.array == ['one']
test_form = TestForm(instance=test_instance)
test_form = TestForm(data=[], instance=test_instance)
assert test_form.is_valid()
assert test_form.cleaned_data == {'array': []}
updated_instance = test_form.save(commit=False)
assert updated_instance.array == []
}}}
"	Bug	closed	Forms	1.10	Normal	fixed	ArrayField postgresql MultipleChoiceField		Accepted	1	0	0	0	0	0