Extract attributes filtering from serializer into adapter.

lib/active_model/serializer.rb

@@ -148,13 +148,8 @@ module ActiveModel
       root || object.class.model_name.to_s.underscore
     end
 
-    def attributes(options = {})
-      attributes =
-        if options[:fields]
-          self.class._attributes & options[:fields]
-        else
-          self.class._attributes.dup
-        end
+    def attributes
+      attributes = self.class._attributes.dup
 
       attributes.each_with_object({}) do |name, hash|
         unless self.class._fragmented

lib/active_model/serializer/adapter/attributes.rb

@@ -57,7 +57,10 @@ module ActiveModel
 
         def resource_object_for(options)
           cache_check(serializer) do
-            serializer.attributes(options)
+            attributes = serializer.attributes
+            attributes.slice!(*options[:fields]) if options[:fields]
+
+            attributes
           end
         end
       end

lib/active_model/serializer/adapter/json_api.rb

@@ -47,7 +47,7 @@ module ActiveModel
 
           fields = options.delete(:fields)
           if fields
-            @fieldset = ActiveModel::Serializer::Fieldset.new(fields, serializer.json_key)
+            @fieldset = ActiveModel::Serializer::Fieldset.new(fields)
           else
             @fieldset = options[:fieldset]
           end
@@ -60,7 +60,7 @@ module ActiveModel
             if serializer.respond_to?(:each)
               serializable_hash_for_collection(options)
             else
-              serializable_hash_for_single_resource(options)
+              serializable_hash_for_single_resource
             end
 
           ApiObjects::JsonApi.add!(hash)
@@ -99,8 +99,8 @@ module ActiveModel
           hash
         end
 
-        def serializable_hash_for_single_resource(options)
-          primary_data = primary_data_for(serializer, options)
+        def serializable_hash_for_single_resource
+          primary_data = primary_data_for(serializer)
           relationships = relationships_for(serializer)
           included = included_resources(@include_tree)
           hash = { data: primary_data }
@@ -134,22 +134,22 @@ module ActiveModel
           { id: id.to_s, type: type }
         end
 
-        def resource_object_for(serializer, options = {})
-          options[:fields] = fieldset && fieldset.fields_for(serializer)
-
+        def resource_object_for(serializer)
           cache_check(serializer) do
-            result = resource_identifier_for(serializer)
-            attributes = serializer.attributes(options).except(:id)
-            result[:attributes] = attributes if attributes.any?
-            result
+            resource_object = resource_identifier_for(serializer)
+            requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
+            attributes = serializer.attributes.except(:id)
+            attributes.slice!(*requested_fields) if requested_fields
+            resource_object[:attributes] = attributes if attributes.any?
+            resource_object
           end
         end
 
-        def primary_data_for(serializer, options)
+        def primary_data_for(serializer)
           if serializer.respond_to?(:each)
-            serializer.map { |s| resource_object_for(s, options) }
+            serializer.map { |s| resource_object_for(s) }
           else
-            resource_object_for(serializer, options)
+            resource_object_for(serializer)
           end
         end
 
@@ -187,7 +187,7 @@ module ActiveModel
           else
             return unless serializer && serializer.object
 
-            primary_data = primary_data_for(serializer, instance_options)
+            primary_data = primary_data_for(serializer)
             relationships = relationships_for(serializer)
             primary_data[:relationships] = relationships if relationships.any?
 

lib/active_model/serializer/fieldset.rb

@@ -1,8 +1,7 @@
 module ActiveModel
   class Serializer
     class Fieldset
-      def initialize(fields, root = nil)
-        @root       = root
+      def initialize(fields)
         @raw_fields = fields
       end
 
@@ -10,27 +9,19 @@ module ActiveModel
         @fields ||= parsed_fields
       end
 
-      def fields_for(serializer)
-        key = serializer.json_key
-        fields[key.to_sym] || fields[key.pluralize.to_sym]
+      def fields_for(type)
+        fields[type.singularize.to_sym] || fields[type.pluralize.to_sym]
       end
 
       private
 
       ActiveModelSerializers.silence_warnings do
-        attr_reader :raw_fields, :root
+        attr_reader :raw_fields
       end
 
       def parsed_fields
         if raw_fields.is_a?(Hash)
           raw_fields.inject({}) { |h, (k, v)| h[k.to_sym] = v.map(&:to_sym); h }
-        elsif raw_fields.is_a?(Array)
-          if root.nil?
-            raise ArgumentError, 'The root argument must be specified if the fields argument is an array.'.freeze
-          end
-          hash = {}
-          hash[root.to_sym] = raw_fields.map(&:to_sym)
-          hash
         else
           {}
         end