Clean up HasOne array wrapping logic

Introduce private _wrap_in_array option for now.

lib/active_model/serializer.rb

@@ -133,8 +133,7 @@ end
           if association.embed_ids?
             hash[association.key] = serialize_ids association
           elsif association.embed_objects?
-            associated_data = send(association.name)
+            hash[association.embedded_key] = serialize association
-            hash[association.embedded_key] = serialize(association, associated_data)
           end
         end
       end
@@ -150,14 +149,14 @@ end
       associations.each_with_object({}) do |(name, association), hash|
         if included_associations.include? name
           if association.embed_in_root?
-            associated_data = Array(send(association.name))
+            hash[association.root_key] = serialize association
-            hash[association.root_key] = serialize(association, associated_data)
           end
         end
       end
     end
 
-    def serialize(association, object)
+    def serialize(association)
+      object = send(association.name)
       association.build_serializer(object, scope: scope).serializable_object
     end
 
@@ -174,6 +173,7 @@ end
       return nil if object.nil?
       hash = attributes
       hash.merge! associations
+      @options[:_wrap_in_array] ? [hash] : hash
     end
     alias_method :serializable_object, :serializable_hash
   end

lib/active_model/serializer/associations.rb

@@ -38,13 +38,6 @@ module ActiveModel
         @serializer_class.new(object, options.merge(@options))
       end
 
-      private
-
-      def use_array_serializer!
-        @options.merge!(each_serializer: @serializer_class)
-        @serializer_class = ArraySerializer
-      end
-
       class HasOne < Association
         def initialize(name, *args)
           super
@@ -53,12 +46,8 @@ module ActiveModel
         end
 
         def build_serializer(object, options = {})
-          if object.respond_to?(:to_ary) && !(@serializer_class && @serializer_class <= ArraySerializer)
+          @serializer_class ||= Serializer.serializer_for(object) || DefaultSerializer
-            use_array_serializer!
+          options[:_wrap_in_array] = embed_in_root?
-          else
-            @serializer_class ||= Serializer.serializer_for(object) || DefaultSerializer
-          end
-
           super
         end
       end
@@ -72,7 +61,8 @@ module ActiveModel
 
         def build_serializer(object, options = {})
           if @serializer_class && !(@serializer_class <= ArraySerializer)
-            use_array_serializer!
+            @options[:each_serializer] = @serializer_class
+            @serializer_class = ArraySerializer
           else
             @serializer_class ||= ArraySerializer
           end

test/unit/active_model/serializer/associations/build_serializer_test.rb

@@ -11,11 +11,8 @@ module ActiveModel
 
         def test_build_serializer_for_array_called_twice
           2.times do
-            serializer      = @association.build_serializer([@post])
+            serializer = @association.build_serializer(@post)
-            each_serializer = serializer.serializer_for(@post)
+            assert_instance_of(PostSerializer, serializer)
-
-            assert_instance_of(ArraySerializer, serializer)
-            assert_instance_of(PostSerializer,  each_serializer)
           end
         end
       end