FEATURE: support staff only custom user fields

config/locales/server.en.yml

@@ -1078,6 +1078,7 @@ en:
     detect_custom_avatars: "Whether or not to check that users have uploaded custom avatars."
     max_daily_gravatar_crawls: "Maximum number of times Discourse will check Gravatar for custom avatars in a day"
     public_user_custom_fields: "A whitelist of custom fields for a user that can be shown publically."
+    staff_user_custom_fields: "A whitelist of custom fields for a user that can be shown to staff."
 
     allow_profile_backgrounds: "Allow users to upload profile backgrounds."
 

config/site_settings.yml

@@ -299,6 +299,9 @@ users:
   public_user_custom_fields:
     type: list
     default: ''
+  staff_user_custom_fields:
+    type: list
+    default: ''
 
 posting:
   min_post_length:

lib/topic_view.rb

@@ -42,6 +42,11 @@ class TopicView
       @user_custom_fields = User.custom_fields_for_ids(@posts.map(&:user_id), SiteSetting.public_user_custom_fields.split('|'))
     end
 
+    if @guardian.is_staff? && SiteSetting.staff_user_custom_fields.present? && @posts
+      @user_custom_fields ||= {}
+      @user_custom_fields.deep_merge!(User.custom_fields_for_ids(@posts.map(&:user_id), SiteSetting.staff_user_custom_fields.split('|')))
+    end
+
     @draft_key = @topic.draft_key
     @draft_sequence = DraftSequence.current(@user, @draft_key)
   end