Change the behavior of route defaults

This commit changes route defaults so that explicit defaults are no
longer required where the key is not part of the path. For example:

  resources :posts, bucket_type: 'posts'

will be required whenever constructing the url from a hash such as a
functional test or using url_for directly. However using the explicit
form alters the behavior so it's not required:

  resources :projects, defaults: { bucket_type: 'projects' }

This changes existing behavior slightly in that any routes which
only differ in their defaults will match the first route rather
than the closest match.

Closes #8814

1 files changed, 7 insertions, 4 deletions

diff --git a/actionpack/lib/action_dispatch/journey/route.rb b/actionpack/lib/action_dispatch/journey/route.rb
index b08ac4b4eb..063302e0f2 100644
--- a/actionpack/lib/action_dispatch/journey/route.rb
+++ b/actionpack/lib/action_dispatch/journey/route.rb
@@ -45,7 +45,7 @@ module ActionDispatch
       end
 
       def required_keys
-        path.required_names.map { |x| x.to_sym } + required_defaults.keys
+        required_parts + required_defaults.keys
       end
 
       def score(constraints)
@@ -79,10 +79,13 @@ module ActionDispatch
         @required_parts ||= path.required_names.map { |n| n.to_sym }
       end
 
+      def required_default?(key)
+        (constraints[:required_defaults] || []).include?(key)
+      end
+
       def required_defaults
-        @required_defaults ||= begin
-          matches = parts
-          @defaults.dup.delete_if { |k,_| matches.include?(k) }
+        @required_defaults ||= @defaults.dup.delete_if do |k,_|
+          parts.include?(k) || !required_default?(k)
         end
       end