Merge pull request #22942 from Edouard-chin/rake-routes-error-message

Better error message when running `rake routes` with CONTROLLER arg:

1 files changed, 18 insertions, 7 deletions

diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index f3a5268d2e..69e6dd5215 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -65,7 +65,7 @@ module ActionDispatch
         routes = collect_routes(routes_to_display)
 
         if routes.none?
-          formatter.no_routes
+          formatter.no_routes(collect_routes(@routes), filter)
           return formatter.result
         end
 
@@ -84,7 +84,8 @@ module ActionDispatch
 
       def filter_routes(filter)
         if filter
-          @routes.select { |route| route.defaults[:controller] == filter }
+          filter_name = filter.underscore.sub(/_controller$/, '')
+          @routes.select { |route| route.defaults[:controller] == filter_name }
         else
           @routes
         end
@@ -136,17 +137,27 @@ module ActionDispatch
         @buffer << draw_header(routes)
       end
 
-      def no_routes
-        @buffer << <<-MESSAGE.strip_heredoc
+      def no_routes(routes, filter)
+        @buffer <<
+        if routes.none?
+          <<-MESSAGE.strip_heredoc
           You don't have any routes defined!
 
           Please add some routes in config/routes.rb.
-
-          For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html.
           MESSAGE
+        elsif missing_controller?(filter)
+          "The controller #{filter} does not exist!"
+        else
+          "No routes were found for this controller"
+        end
+        @buffer << "For more information about routes, see the Rails guide: http://guides.rubyonrails.org/routing.html."
       end
 
       private
+        def missing_controller?(controller_name)
+          [ controller_name.camelize, "#{controller_name.camelize}Controller" ].none?(&:safe_constantize)
+        end
+
         def draw_section(routes)
           header_lengths = ['Prefix', 'Verb', 'URI Pattern'].map(&:length)
           name_width, verb_width, path_width = widths(routes).zip(header_lengths).map(&:max)
@@ -187,7 +198,7 @@ module ActionDispatch
       def header(routes)
       end
 
-      def no_routes
+      def no_routes(*)
         @buffer << <<-MESSAGE.strip_heredoc
           <p>You don't have any routes defined!</p>
           <ul>