Clean up Serializer#build interface and Controller usage

lib/action_controller/serialization.rb

@@ -33,15 +33,16 @@ def use_adapter?
 
     [:_render_option_json, :_render_with_renderer_json].each do |renderer_method|
       define_method renderer_method do |resource, options|
-        builder = ActiveModel::Serializer::Builder.new(resource, options)
-        if builder.serializer?
-          builder.serialization_scope ||= serialization_scope
-          builder.serialization_scope_name = _serialization_scope
-          adapter = builder.adapter
-          super(adapter, options)
-        else
-          super(resource, options)
+        serializable_resource = ActiveModel::Serializer::build(resource, options) do |builder|
+          if builder.serializer?
+            builder.serialization_scope ||= serialization_scope
+            builder.serialization_scope_name = _serialization_scope
+            builder.adapter
+          else
+            resource
+          end
         end
+        super(serializable_resource, options)
       end
     end
 

lib/active_model/serializer.rb

@@ -31,10 +31,15 @@ def self.inherited(base)
     end
 
     # Primary interface to building a serializer (with adapter)
+    # If no block is given, returns the adapter, ready for #as_json/#to_json
+    # Otherwise, yields the builder and returns the contents of the block
     def self.build(resource, options = {})
       builder = Builder.new(resource, options)
-      yield builder if block_given?
-      builder.adapter
+      if block_given?
+        yield builder
+      else
+        builder.adapter
+      end
     end
 
     def self.attributes(*attrs)

test/serializers/meta_test.rb

@@ -95,8 +95,7 @@ def test_meta_is_present_on_arrays_with_root
 
       def load_adapter(options)
         options = options.merge(adapter: :json, serializer: AlternateBlogSerializer)
-        builder = ActiveModel::Serializer::Builder.new(@blog, options)
-        builder.adapter
+        ActiveModel::Serializer.build(@blog, options)
       end
     end
   end