Allow NotFound to specify an optional Location for the resource

app/controllers/application_controller.rb

@@ -136,7 +136,15 @@ class ApplicationController < ActionController::Base
     end
   end
 
-  rescue_from Discourse::NotFound, PluginDisabled  do
+  rescue_from Discourse::NotFound do |e|
+    rescue_discourse_actions(
+      :not_found,
+      404,
+      location: e.location
+    )
+  end
+
+  rescue_from PluginDisabled do |e|
     rescue_discourse_actions(:not_found, 404)
   end
 
@@ -159,10 +167,18 @@ class ApplicationController < ActionController::Base
                        (request.xhr?) ||
                        ((params[:external_id] || '').ends_with? '.json')
 
+    if opts[:location]
+      response.headers['Location'] = opts[:location]
+    end
+
     if show_json_errors
       # HACK: do not use render_json_error for topics#show
       if request.params[:controller] == 'topics' && request.params[:action] == 'show'
-        return render status: status_code, layout: false, text: (status_code == 404 || status_code == 410) ? build_not_found_page(status_code) : I18n.t(type)
+        return render(
+          status: status_code,
+          layout: false,
+          text: (status_code == 404 || status_code == 410) ? build_not_found_page(status_code) : I18n.t(type)
+        )
       end
 
       render_json_error I18n.t(opts[:custom_message] || type), type: type, status: status_code

lib/discourse.rb

@@ -74,7 +74,13 @@ module Discourse
   end
 
   # When something they want is not found
-  class NotFound < StandardError; end
+  class NotFound < StandardError
+    attr_reader :location
+    def initialize(opts = nil)
+      opts ||= {}
+      @location = opts[:location]
+    end
+  end
 
   # When a setting is missing
   class SiteSettingMissing < StandardError; end