Re: Question re django.forms.models.BaseModelFormSet.save_existing_objects()

On 21/12/2015 6:10 PM, James Schneider wrote:
> I have just been digging into django.forms.models.py
> <http://django.forms.models.py> to debug my own code and found
> something which confuses me in both 1.8 and 1.9
>
> django.forms.models.BaseModelFormSet.save_existing_objects() puts
> objects (child model instances) into the
> BaseModelFormSet.deleted_objects list whether they are deleted or not.
>
> Here is the 1.9 code (no need to show 1.8 because they are both more
> or less the same)
>
> 741 def save_existing_objects(self, commit=True):
> 742 self.changed_objects = []
> 743 self.deleted_objects = []
> 744 if not self.initial_forms:
> 745 return []
> 746
> 747 saved_instances = []
> 748 forms_to_delete = self.deleted_forms
> 749 for form in self.initial_forms:
> 750 obj = form.instance
> 751 if form in forms_to_delete:
> 752 # If the pk is None, it means that the
> object can't be
> 753 # deleted again. Possible reason for this
> is that the
> 754 # object was already deleted from the DB.
> Refs #14877.
> 755 if obj.pk <http://obj.pk> is None:
> 756 continue
> 757 self.deleted_objects.append(obj)
> 758 self.delete_existing(obj, commit=commit)
> 759 elif form.has_changed():
> 760 self.changed_objects.append((obj,
> form.changed_data))
> 761
> saved_instances.append(self.save_existing(form, obj, commit=commit))
> 762 if not commit:
> 763 self.saved_forms.append(form)
> 764 return saved_instances
>
> Line 758 will fail and the object will not be deleted if commit ==
> False but line 757 has already added the object to a list.
>
> Is this intended?
>
>
> Wouldn't L757 only get executed if L751 has already determined that the
> particular object/form is supposed to be deleted, meaning that
> self.deleted_objects would only contain objects/forms that were supposed
> to be deleted?

That is true. However, if commit was False that object wouldn't be
deleted but it would still appear in the self.deleted_objects list. My
concern - or more accurately lack of understanding - is that the object
would remain in existence AND appear in the deleted list. This was
precisely what happened in my project and which I was trying to debug.

The symptom in the Admin was a checked box for deleting a child record
which stubbornly stayed there despite the Admin reporting a successful
save.

Mike

>
> -James
>
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