Django: Forcing admin users to enter at least one item in TabularInline

Question

In my admin for an object Chair I have a TabularInline for an arbitrary number of Desk objects. I want every Chair to always

Answer 1

A generic FormSet clean() method for requiring at least one item:

    def clean(self):
        """Check that at least one service has been entered."""
        super(MyFormSet, self).clean()
        if any(self.errors):
            return
        if not any(cleaned_data and not cleaned_data.get('DELETE', False)
                   for cleaned_data in self.cleaned_data):
            raise forms.ValidationError('At least one item required.')

This should work for plain formsets, model formsets and in-line model formsets.