Automatic include directives from filtering on a relationship column?

In the apply filters function:

    def apply_filters(records, filters, options = {})
      required_includes = []

      if filters
        filters.each do |filter, value|
          if _resource_klass._relationships.include?(filter)
            if _resource_klass._relationships[filter].belongs_to?
              records = apply_filter(records, _resource_klass._relationships[filter].foreign_key, value, options)
            else
              required_includes.push(filter.to_s)
              records = apply_filter(records, "#{_resource_klass._relationships[filter].table_name}.#{_resource_klass._relationships[filter].primary_key}", value, options)
            end
          else
            records = apply_filter(records, filter, value, options)
          end
        end
      end

      if required_includes.any?
        records = apply_includes(records, options.merge(include_directives: IncludeDirectives.new(_resource_klass, required_includes, force_eager_load: true)))
      end

      records
    end

I noticed there is a line where the filtered relationships are then added as includes which then get returned.

 if required_includes.any?
        records = apply_includes(records, options.merge(include_directives: IncludeDirectives.new(_resource_klass, required_includes, force_eager_load: true)))
      end

This means that I can never just filter on a relationship column but just return the top level object, I have to return the whole filtered relationship as well.

Is that right? Is that in accordance with the JSON API spec?

Start at the apply_filters function shown in the issue and trace how apply_includes and IncludeDirectives handle required relationship includes. Compare the resulting response behavior with the JSON:API specification, then determine and document whether filtering by a relationship column should return only the top-level resource or also the filtered relationship.