Store diff with line note. It makes possible to see inline notes with proper...

Store diff with line note. It makes possible to see inline notes with proper diff even if MR diff changed

app/models/note.rb

@@ -50,6 +50,9 @@ class Note < ActiveRecord::Base
   scope :inc_author_project, ->{ includes(:project, :author) }
   scope :inc_author, ->{ includes(:author) }
+  serialize :st_diff
+  before_create :set_diff, if: ->(n) { n.noteable_type == 'MergeRequest' && n.line_code.present? }
+
   def self.create_status_change_note(noteable, author, status)
     create({
       noteable: noteable,
@@ -67,22 +70,33 @@ class Note < ActiveRecord::Base
     nil
   end
-  def diff
-    if noteable.diffs.present?
-      noteable.diffs.select do |d|
-        if d.new_path
-          Digest::SHA1.hexdigest(d.new_path) == diff_file_index
-        end
-      end.first
+  def find_diff
+    return nil unless noteable.diffs.present?
+
+    @diff ||= noteable.diffs.find do |d|
+      Digest::SHA1.hexdigest(d.new_path) == diff_file_index if d.new_path
     end
   end
+  def set_diff
+    # First lets find notes with same diff
+    # before iterating over all mr diffs
+    diff = self.noteable.notes.where(line_code: self.line_code).last.try(:diff)
+    diff ||= find_diff
+
+    self.st_diff = diff.to_hash if diff
+  end
+
+  def diff
+    @diff ||= Gitlab::Git::Diff.new(st_diff) if st_diff.respond_to?(:map)
+  end
+
   def diff_file_index
     line_code.split('_')[0]
   end
   def diff_file_name
-    diff.new_path
+    diff.new_path if diff
   end
   def diff_new_line

lib/tasks/migrate/migrate_inline_notes.rake

+desc "GITLAB | Migrate inline notes"
+task migrate_inline_notes: :environment do
+  Note.where(noteable_type: 'MergeRequest').find_each(batch_size: 100) do |note|
+    begin
+      note.set_diff
+      if note.save
+        print '.'
+      else
+        print 'F'
+      end
+    rescue
+      print 'F'
+    end
+  end
+end
+