Add custom LineCodeValidator

app/models/note.rb

@@ -44,7 +44,7 @@ class Note < ActiveRecord::Base
   validates :note, :project, presence: true
   validates :note, uniqueness: { scope: [:author, :noteable_type, :noteable_id] }, if: ->(n) { n.is_award }
   validates :note, inclusion: { in: Emoji.emojis_names }, if: ->(n) { n.is_award }
-  validates :line_code, format: { with: /\A[a-z0-9]+_\d+_\d+\Z/ }, allow_blank: true
+  validates :line_code, line_code: true, allow_blank: true
   # Attachments are deprecated and are handled by Markdown uploader
   validates :attachment, file_size: { maximum: :max_attachment_size }

app/models/sent_notification.rb

@@ -21,7 +21,7 @@ class SentNotification < ActiveRecord::Base
   validates :reply_key, uniqueness: true
   validates :noteable_id, presence: true, unless: :for_commit?
   validates :commit_id, presence: true, if: :for_commit?
-  validates :line_code, format: { with: /\A[a-z0-9]+_\d+_\d+\Z/ }, allow_blank: true
+  validates :line_code, line_code: true, allow_blank: true
   class << self
     def reply_key

app/validators/line_code_validator.rb

+# LineCodeValidator
+#
+# Custom validator for GitLab line codes.
+class LineCodeValidator < ActiveModel::EachValidator
+  PATTERN = /\A[a-z0-9]+_\d+_\d+\z/.freeze
+
+  def validate_each(record, attribute, value)
+    unless value =~ PATTERN
+      record.errors.add(attribute, "must be a valid line code")
+    end
+  end
+end