Add an attributes bag class as a GitalyClient helper

lib/gitlab/gitaly_client/attributes_bag.rb

+module Gitlab
+  module GitalyClient
+    # This module expects an `ATTRS` const to be defined on the subclass
+    # See GitalyClient::WikiFile for an example
+    module AttributesBag
+      extend ActiveSupport::Concern
+
+      included do
+        attr_accessor(*const_get(:ATTRS))
+      end
+
+      def initialize(params)
+        params = params.with_indifferent_access
+
+        attributes.each do |attr|
+          instance_variable_set("@#{attr}", params[attr])
+        end
+      end
+
+      def ==(other)
+        attributes.all? do |field|
+          instance_variable_get("@#{field}") == other.instance_variable_get("@#{field}")
+        end
+      end
+
+      def attributes
+        self.class.const_get(:ATTRS)
+      end
+    end
+  end
+end

lib/gitlab/gitaly_client/diff.rb

 module Gitlab
   module GitalyClient
     class Diff
-      FIELDS = %i(from_path to_path old_mode new_mode from_id to_id patch overflow_marker collapsed).freeze
+      ATTRS = %i(from_path to_path old_mode new_mode from_id to_id patch overflow_marker collapsed).freeze
 
-      attr_accessor(*FIELDS)
-
-      def initialize(params)
-        params.each do |key, val|
-          public_send(:"#{key}=", val) # rubocop:disable GitlabSecurity/PublicSend
-        end
-      end
-
-      def ==(other)
-        FIELDS.all? do |field|
-          public_send(field) == other.public_send(field) # rubocop:disable GitlabSecurity/PublicSend
-        end
-      end
+      include AttributesBag
     end
   end
 end

lib/gitlab/gitaly_client/diff_stitcher.rb

@@ -12,7 +12,7 @@ module Gitlab
 
         @rpc_response.each do |diff_msg|
           if current_diff.nil?
-            diff_params = diff_msg.to_h.slice(*GitalyClient::Diff::FIELDS)
+            diff_params = diff_msg.to_h.slice(*GitalyClient::Diff::ATTRS)
             # gRPC uses frozen strings by default, and we need to have an unfrozen string as it
             # gets processed further down the line. So we unfreeze the first chunk of the patch
             # in case it's the only chunk we receive for this diff.

lib/gitlab/gitaly_client/wiki_file.rb

 module Gitlab
   module GitalyClient
     class WikiFile
-      FIELDS = %i(name mime_type path raw_data).freeze
+      ATTRS = %i(name mime_type path raw_data).freeze
 
-      attr_accessor(*FIELDS)
-
-      def initialize(params)
-        params = params.with_indifferent_access
-
-        FIELDS.each do |field|
-          instance_variable_set("@#{field}", params[field])
-        end
-      end
+      include AttributesBag
     end
   end
 end

lib/gitlab/gitaly_client/wiki_page.rb

 module Gitlab
   module GitalyClient
     class WikiPage
-      FIELDS = %i(title format url_path path name historical raw_data).freeze
+      ATTRS = %i(title format url_path path name historical raw_data).freeze
 
-      attr_accessor(*FIELDS)
+      include AttributesBag
 
       def initialize(params)
-        params = params.with_indifferent_access
-
-        FIELDS.each do |field|
-          instance_variable_set("@#{field}", params[field])
-        end
+        super
 
         # All gRPC strings in a response are frozen, so we get an unfrozen
         # version here so appending to `raw_data` doesn't blow up.