1 files changed, 36 insertions, 6 deletions

diff --git a/lib/chef_zero/endpoints/rest_object_endpoint.rb b/lib/chef_zero/endpoints/rest_object_endpoint.rb
index 9e978b4..efadf82 100644
--- a/lib/chef_zero/endpoints/rest_object_endpoint.rb
+++ b/lib/chef_zero/endpoints/rest_object_endpoint.rb
@@ -21,12 +21,11 @@ module ChefZero
       def put(request)
         # We grab the old body to trigger a 404 if it doesn't exist
         old_body = get_data(request)
-        request_json = FFI_Yajl::Parser.parse(request.body, :create_additions => false)
-        key = identity_keys.map { |k| request_json[k] }.select { |v| v }.first
-        key ||= request.rest_path[-1]
+
         # If it's a rename, check for conflict and delete the old value
-        rename = key != request.rest_path[-1]
-        if rename
+        if is_rename?(request)
+          key = identity_key_value(request)
+
           begin
             create_data(request, request.rest_path[0..-2], key, request.body, :data_store_exceptions)
           rescue DataStore::DataAlreadyExistsError
@@ -46,18 +45,49 @@ module ChefZero
         already_json_response(200, populate_defaults(request, result))
       end
 
-      def patch_request_body(request)
+      # Merge the request body with the existing data, if one exists in
+      # the data store
+      #
+      # @param [ChefZero::RestRequest] request
+      # @param [Hash] options
+      # @option options [Symbol, Array<Symbol>] :except (nil) Key(s) from
+      #   the existing data to discard
+      def patch_request_body(request, options={})
         existing_value = get_data(request, nil, :nil)
+
         if existing_value
           request_json = FFI_Yajl::Parser.parse(request.body, :create_additions => false)
           existing_json = FFI_Yajl::Parser.parse(existing_value, :create_additions => false)
+
+          if options[:except]
+            Array(options[:except]).each do |except_key|
+              existing_json.delete(except_key)
+            end
+          end
+
           merged_json = existing_json.merge(request_json)
+
           if merged_json.size > request_json.size
             return FFI_Yajl::Encoder.encode(merged_json, :pretty => true)
           end
         end
+
         request.body
       end
+
+      private
+
+      # Get the value of the (first existing) identity key from the request body or nil
+      def identity_key_value(request)
+        request_json = FFI_Yajl::Parser.parse(request.body, :create_additions => false)
+        identity_keys.map { |k| request_json[k] }.compact.first
+      end
+
+      # Does this request change the value of the identity key?
+      def is_rename?(request)
+        return false unless key = identity_key_value(request)
+        key != request.rest_path[-1]
+      end
     end
   end
 end