JsonApi adapter: serialize association

lib/active_model/serializer/adapter/json_api_adapter.rb

@@ -3,19 +3,33 @@ module ActiveModel
     class Adapter
       class JsonApiAdapter < Adapter
         def serializable_hash(options = {})
-          hash = serializer.attributes
+          @hash = serializer.attributes
 
-          associations = serializer.associations(only: [:id]).each_with_object({}) do |(attr, value), h|
-            h[attr] = case value
-                       when ActiveModel::Serializer::ArraySerializer
-                         value.map(&:id)
-                       when ActiveModel::Serializer
-                         # process belongs_to association
-                       else
-                         # what?
-                       end
+          serializer.associations.each do |name, association|
+            @hash[:links] ||= {}
+            @hash[:linked] ||= {}
+            if association.respond_to?(:each)
+              add_links(name, association)
+            else
+              add_link(name, association)
+            end
           end
-          hash.merge(associations)
+          @hash
+        end
+
+        def add_links(name, serializers)
+          @hash[:links][name] ||= []
+          @hash[:linked][name] ||= []
+          @hash[:links][name] += serializers.map(&:id)
+          @hash[:linked][name] += serializers.map(&:attributes)
+        end
+
+        def add_link(name, serializer)
+          plural_name = name.to_s.pluralize.to_sym
+          @hash[:linked][plural_name] ||= []
+
+          @hash[:links][name] = serializer.id
+          @hash[:linked][plural_name].push serializer.attributes
         end
       end
     end