Possible bug in 1.8 admin app for foreign key handling.

Scott Gibson

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Aug 5, 2015, 5:36:10 PM8/5/15

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The django admin app is requiring a foreign key to be populated even though the model is defined and migrated with null=true and blank=true.

What I've found is that the admin app will treat the field as required if the associated AdminForm(forms.ModelForm) overrides the fields collection for the foreign key field.

e.g. the init for the admin class has something like this in it:

self.fields['FKFIELD'] = ContextNameChoiceField(queryset=FKMODEL.objects.all())

For reference ContextNameChoiceField is sub class of ModelChoiceField which is handling a specific call to get a user friendly list of choice values.

If the self.fields* line is commented out the field is no longer required but now the values to choose from aren't friendly. To explain friendly.. the FK is to the bottom of a hierarchical structure. e.g. Region/Country/Site where Site is the FK relate but the same Site name can exist in multiple countries so Site name alone isn't unique. The ContextNameChoiceField class produces a site name that includes the region/country/site to aide the selection of the correct site. It's done this way to allow for a single assignment versus a 3 FK assignment using region, country, site individually.

My guess is that the admin class init override is clearing some settings for the FKField that would normally come from the model. I'm not sure how to look into what's happening on object construction to verify though.

James Bennett

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Aug 5, 2015, 5:38:36 PM8/5/15

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Have you tried setting "required=False" in your custom field override?

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Scott Gibson

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Aug 5, 2015, 7:30:23 PM8/5/15

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I've not and I'm not sure how or where to do that.

Scott Gibson

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Aug 5, 2015, 7:42:15 PM8/5/15

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Nevermind.. You provided the grain of truth I needed and I think it's working now.. added required=false to the constructor call.. after seeing what was in the fields collection with the debugger.