Hi Jon, On 07/02/2014 09:06 PM, Jon Dufresne wrote: > I'm reporting this to the developers list as I feel this shows a > shortfall in (to me) expected behavior. I'm not sure this is exactly a > bug or simply a use case the unique validation wasn't designed for. > > Basically, sometimes I want to create model formsets that use a > limited number of model fields. These model fields may have a unique > constraint using unique_together. The other field (or fields) of > unique together may not be included in the formset. Upon validating > the form, unique_together fields are only checked if all fields are > contained in the form. This means, my unique fields will not be > validated automatically. To achieve the validation I usually have to > copy parts of Django form validation, missing out on DRY. > > I think one solution would be for model formsets to have a "static" or > "constant" fields argument. This could be a single value per field > that all forms in the formset would share for a particular set of > fields. These fields would not be a part of the rendered form, but > could be used for validating the forms and creating new models > instances. Thoughts?
I agree this is a problem that should be fixed; it is tracked in https://code.djangoproject.com/ticket/13091 and there is already a history of proposals for fixing it. I think your proposed fix is a new one, though. It's less flexible than the context-manager API I had proposed at one time [1], but it may cover the 80% case adequately, and has the major advantage of not requiring any changes in the code that checks the validity of the form. There is already a way to get "default" values for excluded fields into a ModelForm: pass it an unsaved "instance" at form instantiation, with those fields set on it. So it feels odd to me to add a new way to pass in such values. But passing in an instance doesn't trigger full-model validation, and making it do that could break existing code, so we'd still need some way to flag that you want that behavior. Hmm... Carl [1] https://groups.google.com/d/topic/django-developers/PT17cgDSOw8/discussion
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