Opened 8 years ago
Closed 6 years ago
#27560 closed Bug (invalid)
Formset.save() crashes for model with foreign key to concrete base model
Reported by: | Lorenzo Peña | Owned by: | nobody |
---|---|---|---|
Component: | Forms | Version: | 1.9 |
Severity: | Normal | Keywords: | formset inline_formset inline_formsetfactory |
Cc: | Triage Stage: | Accepted | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
Model hierharchy
class ConcreteBase(models.Model): ... class Descendant(ConcreteBase): ...
Master / Detail type models (e.g. Order and OrderDetail)
class MasterModel(models.Model): ... class DetailModel(models.Model): master = models.ForeignKey(MasterModel, ...) concrete_base = models.ForeignKey(ConcreteBase, ...)
Form definition
class MasterModelForm(forms.ModelForm): ... class DetailModelForm(forms.ModelForm): ... # master excluded from fields as will be manually added in view ...
Formset definition
DetailModelFormset = inlineformset_factory(MasterModel, DetailModel, form=DetailModelForm)
View definition
from django.views.generic.edit import CreateView #### <---- the error only happens on create view of MasterModel class MasterModelAdd(CreateView): model = MasterModel form_class = MasterModelForm ... def form_valid(self, form): master_instance = form.save() detail_formset = DetailModelFormset()(self.request.POST) detail_instances = detail_formset.save(commit=False) ### <------ this line raises the error for detail_instance in detail_instances: ### <----- it never gets here detail_instance.master = master_instance detail_instance.save()
When calling formset.save() I'm getting an error from django/forms/models.py (line 910) regardless of the value of commit passed.
910: pk_value = getattr(self.instance, self.fk.remote_field.field_name) 911: setattr(obj, self.fk.get_attname(), getattr(pk_value, 'pk', pk_value))
The getattr call fails
if I wrap both lines in: if hasattr(self.instance, self.fk.remote_field.field_name):
it works good.
Not sure if the condition is the way to fix the bug or it's just preventing the original cause from happening.
Change History (8)
comment:1 by , 8 years ago
Summary: | Formset.save for model with foreign key to concrete base model → Formset.save() crashes for model with foreign key to concrete base model |
---|---|
Type: | Uncategorized → Bug |
comment:2 by , 8 years ago
Description: | modified (diff) |
---|
comment:3 by , 8 years ago
Updated ticket to expand context so that bug may be (hopefully) reproduced.
comment:4 by , 8 years ago
This report is awfully complicated and without spending more than a few minutes investigating I can't say whether or not this is a bug in Django or in your code. One thing to try might be: DetailModelFormset(self.request.POST, instance=master_instance)
.
It seems like excluding master
from DetailModelForm
may also be related. (How can you have an inline formset without the field linking the subforms to the parent?)
It would be nice if you do more to confirm that this is actually a bug, such as by using our support channels. Putting together a sample project with a test case that someone could download to quickly reproduce the issue would also help.
comment:5 by , 8 years ago
I'll have to investigate, but for the record:
- In this view, I'm creating master and details at the same time, so I don't have really anything to pass because nothing exists yet.
- Regarding the fact that I'm omitting the link to master, do you suggest a hidden field?
- This exact pattern works in at least one more place in my codebase, only crashing when the abstract base is involved in the child formset.
comment:6 by , 8 years ago
Triage Stage: | Unreviewed → Accepted |
---|
I haven't investigated any further but tentatively accepting.
comment:7 by , 6 years ago
I've tested this and found two issues with your code in form_valid
:
... detail_formset = DetailModelFormset(self.request.POST) <---- there was a bug in your previous code: DetailModelFormset()(self.request.POST) if detail_formset.is_valid(): <--- you were missing formset validation detail_instances = detail_formset.save(commit=False) ...
After fixing that, the code works fine.
comment:8 by , 6 years ago
Resolution: | → invalid |
---|---|
Status: | new → closed |
Looks like it was a bug in my code.
Could you include more complete details about how to reproduce the issue? My try to reproduce gives
save() prohibited to prevent data loss due to unsaved related object 'some_model'.
atformset.save()
.