Serializer#serializer_from_options refactoring and small changes in S…

…erializer#associations

lib/active_model/serializer.rb

@@ -220,24 +220,25 @@ def associations
         self.class._reflections.dup.each do |reflection|
           name = reflection.name
           association_value = send(name)
-          serializer_class = ActiveModel::Serializer.serializer_for(association_value, reflection.options)
+          reflection_options = reflection.options.dup
+          serializer_class = ActiveModel::Serializer.serializer_for(association_value, reflection_options)
 
           if serializer_class
             begin
               serializer = serializer_class.new(
                 association_value,
-                options.except(:serializer).merge(serializer_from_options(reflection.options))
+                serializer_options(reflection_options)
               )
             rescue ActiveModel::Serializer::ArraySerializer::NoSerializerError
               virtual_value = association_value
               virtual_value = virtual_value.as_json if virtual_value.respond_to?(:as_json)
-              reflection.options[:virtual_value] = virtual_value
+              reflection_options[:virtual_value] = virtual_value
             end
           elsif !association_value.nil? && !association_value.instance_of?(Object)
-            reflection.options[:virtual_value] = association_value
+            reflection_options[:virtual_value] = association_value
           end
 
-          y.yield Association.new(name, serializer, reflection.options)
+          y.yield Association.new(name, serializer, reflection_options)
         end
       end
     end
@@ -248,11 +249,12 @@ def self.serializers_cache
 
     private
 
-    def serializer_from_options(options)
-      opts = {}
-      serializer = options.fetch(:serializer, nil)
-      opts[:serializer] = serializer if serializer
-      opts
+    def serializer_options(reflection_options)
+      serializer = reflection_options.fetch(:serializer, nil)
+
+      serializer_options = options.except(:serializer)
+      serializer_options[:serializer] = serializer if serializer
+      serializer_options
     end
 
     attr_reader :options