Use serialize_keys as part of highlight diff cache

This assures that old cache is not used if we change format of
cached data.

2 files changed, 4 insertions, 6 deletions

diff --git a/lib/gitlab/diff/file_collection/merge_request_diff.rb b/lib/gitlab/diff/file_collection/merge_request_diff.rb
index c358ae428cf..be25e1bab21 100644
--- a/lib/gitlab/diff/file_collection/merge_request_diff.rb
+++ b/lib/gitlab/diff/file_collection/merge_request_diff.rb
@@ -34,7 +34,7 @@ module Gitlab
         end
 
         def cache_key
-          [@merge_request_diff, 'highlighted-diff-files', diff_options]
+          [@merge_request_diff, 'highlighted-diff-files', Gitlab::Diff::Line::SERIALIZE_KEYS, diff_options]
         end
 
         private
diff --git a/lib/gitlab/diff/line.rb b/lib/gitlab/diff/line.rb
index 2b3ebfbb9ff..1faf7770634 100644
--- a/lib/gitlab/diff/line.rb
+++ b/lib/gitlab/diff/line.rb
@@ -1,6 +1,8 @@
 module Gitlab
   module Diff
     class Line
+      SERIALIZE_KEYS = %i(line_code text type index old_pos new_pos).freeze
+
       attr_reader :line_code, :type, :index, :old_pos, :new_pos
       attr_writer :rich_text
       attr_accessor :text
@@ -19,13 +21,9 @@ module Gitlab
         new(hash[:text], hash[:type], hash[:index], hash[:old_pos], hash[:new_pos], line_code: hash[:line_code])
       end
 
-      def serialize_keys
-        @serialize_keys ||= %i(line_code text type index old_pos new_pos)
-      end
-
       def to_hash
         hash = {}
-        serialize_keys.each { |key| hash[key] = send(key) } # rubocop:disable GitlabSecurity/PublicSend
+        SERIALIZE_KEYS.each { |key| hash[key] = send(key) } # rubocop:disable GitlabSecurity/PublicSend
         hash
       end