Where get_serializer_class() is used to determine which serializer would be used for a ModelViewSet, it doesn't re-create the same environment as DRF would use when servicing an actual API request, and so it may return different results (and thus incorrect documentation).

As an example, I have the following method, which uses a cut-down serializer for list actions, and a full-content serializer for retrieve actions:

class FooViewSet(viewsets.ReadOnlyModelViewSet):
 queryset = Foo.objects.all()
 def get_serializer_class(self):
 if hasattr(self, 'action'):
 if self.action == 'list':
 return FooListSerializer
 elif self.action == 'retrieve':
 return FooSerializer
 return serializers.Default

drfdocs doesn't currently set the self.action member before calling get_serializer_class(), so it gets the default serializer with no fields, whereas an actual API request would get either the FooSerializer or the FooListSerializer.