Validating delete on django-admin inline forms - django

Question

I am trying to perform a validation such that you cannot delete a user if he's an admin. I'd therefore like to check and raise an error if there's a user who's an admin and has been marked for deletion.
This is my inline ModelForm
class UserGroupsForm(forms.ModelForm):
class Meta:
model = UserGroups
def clean(self):
delete_checked = self.fields['DELETE'].widget.value_from_datadict(
self.data, self.files, self.add_prefix('DELETE'))
if bool(delete_checked):
#if user is admin of group x
raise forms.ValidationError('You cannot delete a user that is the group administrator')
return self.cleaned_data
The if bool(delete_checked): condition returns true and stuff inside the if block gets executed but for some reason this validation error is never raised. Could someone please explain to me why?
Better yet if there's another better way to do this please let me know

Answer 1

The solution I found was to clean in the InlineFormSet instead of the ModelForm
class UserGroupsInlineFormset(forms.models.BaseInlineFormSet):
def clean(self):
delete_checked = False
for form in self.forms:
try:
if form.cleaned_data:
if form.cleaned_data['DELETE']:
delete_checked = True
except AttributeError:
pass
if delete_checked:
raise forms.ValidationError(u'You cannot delete a user that is the group administrator')

Answer 2

Although #domino's answer may work for now, the "kinda" recommended approach is to use formset's self._should_delete_form(form) function together with self.can_delete.
There's also the issue of calling super().clean() to perform standard builtin validation. So the final code may look like:
class UserGroupsInlineFormset(forms.models.BaseInlineFormSet):
def clean(self):
super().clean()
if any(self.errors):
return # Don't bother validating the formset unless each form is valid on its own
for form in self.forms:
if self.can_delete and self._should_delete_form(form):
if <...form.instance.is_admin...>:
raise ValidationError('...')

Answer 3

Adding to domino's Answer:
In some other scenarios, Sometimes user wants to delete and add object in the same time, so in this case delete should be fine!
Optimized version of code:
class RequiredImageInlineFormset(forms.models.BaseInlineFormSet):
""" Makes inline fields required """
def clean(self):
# get forms that actually have valid data
count = 0
delete_checked = 0
for form in self.forms:
try:
if form.cleaned_data:
count += 1
if form.cleaned_data['DELETE']:
delete_checked += 1
if not form.cleaned_data['DELETE']:
delete_checked -= 1
except AttributeError:
# annoyingly, if a subform is invalid Django explicity raises
# an AttributeError for cleaned_data
pass
# Case no images uploaded
if count < 1:
raise forms.ValidationError(
'At least one image is required.')
# Case one image added and another deleted
if delete_checked > 0 and ProductImage.objects.filter(product=self.instance).count() == 1:
raise forms.ValidationError(
"At least one image is required.")