ModelForm has_changed on ChoiceFields reports always True if an initial argument is given

[s3h10r]

example model + form:

class Host(models.Model):
    DM=0
    PP=1
    KIND_CHOICES = (
        (DM, 'native mpio'),
        (PP, 'PowerPath'),
    )
    mpio = models.IntegerField(choices=KIND_CHOICES, default=DM)

class HostForm(ModelForm):
    DM=0
    PP=1
    KIND_CHOICES = (
        (DM, 'native mpio'),
        (PP, 'PowerPath'),
    )

    mpio = forms.ChoiceField(choices=KIND_CHOICES, label="Multipathing Software", required=True, initial=DM)

    class Meta:
        model = Host

testcase:

from formprob16.models import Host
from formprob16.forms import HostForm


fm = HostForm() # unbound
fm = HostForm({'mpio' : 0 }) # bound 

print "has_changed:", fm.has_changed()
print "changed_data:", fm.changed_data

output in Django 1.5.5 (and 1.4) is as expected:

>>> has_changed: False
>>> changed_data: []

output in Django 1.6.2 says the form-content was changed:

>>> has_changed: True
>>> changed_data: ['mpio']

If the initial argument is not used / the Form is just derived from the model like in the following example:

class HostForm(ModelForm):

    class Meta:
        model = Host

it works fine in 1.6.2 too, but i think that's not the expected behaviour (or: at least not expected by me ;).

[Claude Paroz]

I can reproduce what you describe. However, the proper field to use here should be a TypedChoiceField(..., coerce=int). I'll keep the ticket open to see if another core developer has another opinion on the matter, or if something should be added in the documentation.

[s3h10r]

@claudep: Thanks! I wasn't aware of this / just stumbled into the pitfall of changed behaviour (could not find much about .has_changed() in the docs). TypedChoiceField works fine.

[Tim Graham]

#21792 is for documenting ModelForm.has_changed().