Serializers should know how to serializer themselves

Author: bf4

lib/active_model/serializer.rb

@@ -185,6 +185,37 @@ def read_attribute_for_serialization(attr)
       end
     end
 
+    def serialize(options, adapter_options, adapter_instance, include_tree)
+      cached_attributes(options[:fields], adapter_instance)
+        .merge(cached_relationships(adapter_options, adapter_instance, include_tree))
+    end
+
+    def cached_relationships(adapter_options, adapter_instance, include_tree)
+      relationships = {}
+      associations(include_tree).each do |association|
+        relationships[association.key] =
+          if association.options[:virtual_value]
+            association.options[:virtual_value]
+          elsif association.serializer && association.serializer.object
+            association_serializer = association.serializer
+            association_options = adapter_options.merge(include: include_tree[association.key])
+            association_include_tree = ActiveModel::Serializer::IncludeTree.from_include_args(association_options[:include] || '*')
+            if association_serializer.respond_to?(:each)
+              association_options[:cached_attributes] ||= ActiveModel::Serializer.cache_read_multi(association_serializer, adapter_instance, association_include_tree)
+              association_serializer.map do |serializer|
+                serializer.serialize(association_options, adapter_options, adapter_instance, association_include_tree)
+              end
+            else
+              association_serializer.serialize(association_options, adapter_options, adapter_instance, association_include_tree)
+            end
+          else
+            nil
+          end
+      end
+
+      relationships
+    end
+
     protected
 
     attr_accessor :instance_options

lib/active_model_serializers/adapter/attributes.rb

@@ -10,42 +10,16 @@ def serializable_hash(options = nil)
         options = serialization_options(options)
 
         if serializer.respond_to?(:each)
-          serializable_hash_for_collection(options)
+          serializer.map do |element|
+            element.serialize(options, instance_options, self, @include_tree)
+          end
         else
-          serializable_hash_for_single_resource(options)
+          serializer.serialize(options, instance_options, self, @include_tree)
         end
       end
 
       private
 
-      def serializable_hash_for_collection(options)
-        instance_options[:cached_attributes] ||= ActiveModel::Serializer.cache_read_multi(serializer, self, @include_tree)
-        serializer.map { |s| Attributes.new(s, instance_options).serializable_hash(options) }
-      end
-
-      def serializable_hash_for_single_resource(options)
-        resource = serializer.cached_attributes(options[:fields], self)
-        relationships = resource_relationships(options)
-        resource.merge(relationships)
-      end
-
-      def resource_relationships(options)
-        relationships = {}
-        serializer.associations(@include_tree).each do |association|
-          relationships[association.key] = relationship_value_for(association, options)
-        end
-
-        relationships
-      end
-
-      def relationship_value_for(association, options)
-        return association.options[:virtual_value] if association.options[:virtual_value]
-        return unless association.serializer && association.serializer.object
-
-        opts = instance_options.merge(include: @include_tree[association.key])
-        Attributes.new(association.serializer, opts).serializable_hash(options)
-      end
-
       # no-op: Attributes adapter does not include meta data, because it does not support root.
       def include_meta(json)
         json