Add notes for the temporary implementation about errors

lib/droonga/distributor_plugin.rb

@@ -49,6 +49,11 @@ def process_error(command, error, arguments)
       end
     end
 
+    #XXX Now, default scatterer/broadcaster/reducer/gatherer includes
+    #    definitions to merge errors in the body. However, this makes
+    #    the term "errors" reserved, so plugins cannot use their custom
+    #    "errors" in the body. This must be rewritten. 
+
     def scatterer(message, key)
       {
         "command" => message["type"],

lib/droonga/handler_messenger.rb

@@ -63,6 +63,9 @@ def error(status_code, body)
                                      "body" => body)
         @replier.reply(response)
       else
+        #XXX This is just a temporary solution. We should rewrite this,
+        #    to put errors outside of the message body. Otherwise
+        #    plugins cannot use the name "errors" for their message body.
         body = {
           "id"    => @message.id,
           "input" => "errors",

lib/droonga/output_adapter.rb

@@ -47,6 +47,7 @@ def adapt(message)
     end
 
     private
+    #XXX This is just a temporary solution. We should handle errors without "body", for safety.
     def adapt_errors(output_message)
       if output_message.body.include?("errors")
         errors = output_message.body["errors"]