Fix shorthand routes where controller and action are in the scope

Merge `:action` from routing scope and assign endpoint if both `:controller`
and `:action` are present. The endpoint assignment only occurs if there is
no `:to` present in the options hash so should only affect routes using the
shorthand syntax (i.e. endpoint is inferred from the the path).

Fixes #9856

Backport of 37b4276

1 files changed, 8 insertions, 0 deletions

diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index d71b21efc3..bfa816798d 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -779,6 +779,10 @@ module ActionDispatch
             child
           end
 
+          def merge_action_scope(parent, child) #:nodoc:
+            child
+          end
+
           def merge_path_names_scope(parent, child) #:nodoc:
             merge_options_scope(parent, child)
           end
@@ -1253,6 +1257,10 @@ module ActionDispatch
             paths = [path] + rest
           end
 
+          if @scope[:controller] && @scope[:action]
+            options[:to] ||= "#{@scope[:controller]}##{@scope[:action]}"
+          end
+
           path_without_format = path.to_s.sub(/\(\.:format\)$/, '')
           if using_match_shorthand?(path_without_format, options)
             options[:to] ||= path_without_format.gsub(%r{^/}, "").sub(%r{/([^/]*)$}, '#\1')