Hey Tom,

We have quite a few base serializers that have their own methods and fields, etc., and serializer subclasses that use a subset of these fields declared in the parent.

This setup breaks after upgrading to 3.0 due to this particular configuration assertion:

ImproperlyConfigured: Field `blah_field` has been declared on serializer
`MySerializer`, but is missing from `Meta.fields`.

I do not see the point of this assertion, as inheritance worked as expected before, which allowed for cleaner and more extensible serializers. Do you remember why this was added?

Also, is there a clean way to work around this assertion? Currently I have a hack in the top-level serializer to work around this limitation, which makes this aspect of rest_framework to behave how it used to in 2.4:

class BaseSerializer(serializers.ModelSerializer):

  def get_fields(self):
    # hack; see rest_framework issue #2388
    declared_fields     = copy.deepcopy(self._declared_fields)
    meta_field_names    = getattr(self.Meta, 'fields', None)
    new_declared_fields = OrderedDict()

    for field_name in meta_field_names:
      if field_name not in declared_fields:
        continue
      new_declared_fields[field_name] = declared_fields[field_name]

    self._declared_fields = new_declared_fields

    return super(BaseSerializer, self).get_fields()

P.S. For reference, this validation addition was made in this commit: 87734be