1 files changed, 20 insertions, 15 deletions
diff --git a/app/mailers/notify.rb b/app/mailers/notify.rb
index 576caea4c10..3683f2ea9a9 100644
--- a/app/mailers/notify.rb
+++ b/app/mailers/notify.rb
@@ -71,24 +71,18 @@ class Notify < BaseMailer
     address.format
   end
 
-  # Look up a User by their ID and return their email address
+  # Look up a User's notification email for a particular context.
+  # Can look up by their ID or can accept a User object.
   #
-  # recipient_id       - User ID
+  # recipient          - User object OR a User ID
   # notification_group - The parent group of the notification
   #
   # Returns a String containing the User's email address.
-  def recipient(recipient_id, notification_group = nil)
-    @current_user = User.find(recipient_id)
-    group_notification_email = nil
+  def recipient(recipient, notification_group = nil)
+    user = recipient if recipient.is_a?(User)
+    user ||= User.find(recipient)
 
-    if notification_group
-      notification_settings = notification_group.notification_settings_for(@current_user, hierarchy_order: :asc)
-      group_notification_email = notification_settings.find { |n| n.notification_email.present? }&.notification_email
-    end
-
-    # Return group-specific email address if present, otherwise return global
-    # email address
-    group_notification_email || @current_user.notification_email
+    user.notification_email_for(notification_group)
   end
 
   # Formats arguments into a String suitable for use as an email subject
@@ -131,9 +125,8 @@ class Notify < BaseMailer
   def mail_thread(model, headers = {})
     add_project_headers
     add_unsubscription_headers_and_links
+    add_model_headers(model)
 
-    headers["X-GitLab-#{model.class.name}-ID"] = model.id
-    headers["X-GitLab-#{model.class.name}-IID"] = model.iid if model.respond_to?(:iid)
     headers['X-GitLab-Reply-Key'] = reply_key
 
     @reason = headers['X-GitLab-NotificationReason']
@@ -202,6 +195,18 @@ class Notify < BaseMailer
     @reply_key ||= SentNotification.reply_key
   end
 
+  # This method applies threading headers to the email to identify
+  # the instance we are discussing.
+  #
+  # All model instances must have `#id`, and may implement `#iid`.
+  def add_model_headers(object)
+    # Use replacement so we don't strip the module.
+    prefix = "X-GitLab-#{object.class.name.gsub(/::/, '-')}"
+
+    headers["#{prefix}-ID"] = object.id
+    headers["#{prefix}-IID"] = object.iid if object.respond_to?(:iid)
+  end
+
   def add_project_headers
     return unless @project