I agree with Marc that so many ways to do things isn't ideal, but I don't
see a different simple way to accommodate Peter's use case, so +0 to adding
get_exclude().
On Saturday, June 6, 2015 at 11:44:53 AM UTC-4, Peter J. Farrell wrote:
>
> In our case, we need to dynamically include additional "exclude" fields in
> our VersionableAdmin and not override the selections the developer has set
> in their subclass. There are two options to accomplished this:
>
> 1) Override get_form() which is messy because you can't just call super
> here and modify things. This is a lot of code duplication to just get at
> the exclude
>
> def get_form(self, request, obj=None, **kwargs):
> """
> Returns a Form class for use in the admin add view. This is used by
> add_view and change_view.
> """
> if 'fields' in kwargs:
> fields = kwargs.pop('fields')
> else:
> fields = flatten_fieldsets(self.get_fieldsets(request, obj))
> if self.exclude is None:
> exclude = []
> else:
> exclude = list(self.exclude)
> exclude.extend(self.get_readonly_fields(request, obj))
> if self.exclude is None and hasattr(self.form, '_meta') and
> self.form._meta.exclude:
> # Take the custom ModelForm's Meta.exclude into account only if the
> # ModelAdmin doesn't define its own.
> exclude.extend(self.form._meta.exclude)
> # if exclude is an empty list we pass None to be consistent with the
> # default on modelform_factory
> exclude = exclude or None
> defaults = {
> "form": self.form,
> "fields": fields,
> "exclude": exclude,
> "formfield_callback": partial(self.formfield_for_dbfield,
> request=request),
> }
> defaults.update(kwargs)
>
> if defaults['fields'] is None and not
> modelform_defines_fields(defaults['form']):
> defaults['fields'] = forms.ALL_FIELDS
>
> try:
> return modelform_factory(self.model, **defaults)
> except FieldError as e:
> raise FieldError('%s. Check fields/fieldsets/exclude attributes of
> class %s.'
> % (e, self.__class__.__name__))
>
>
> 2) Build your own descriptor for exclude:
>
> @property
> def exclude(self):
> """
> Custom descriptor for exclude since there is no get_exclude method to be
> overridden
> """
> exclude = self.VERSIONED_EXCLUDE
>
> if super(VersionedAdmin, self).exclude is not None:
> # Force cast to list as super exclude could return a tuple
> exclude = list(super(VersionedAdmin, self).exclude) + exclude
>
> return exclude
>
>
> But then this trips the _check_exclude check in ModelAdminChecks for not
> being a list or tuple. So you have to subclass that:
>
> class VersionedAdminChecks(ModelAdminChecks):
> def _check_exclude(self, cls, model):
> """
> Required to suppress error about exclude not being a tuple since we
> are using @property to dynamically change it
> """
> return []
>
>
> All of this is a lot of effort just to get at dynamic exclude where
> get_exclude() fits the current pattern used in the admin in the current
> code base.
>
>
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