Add support for calling nested direct routes (#28462)

Not all requirements can be expressed in terms of polymorphic url
options so add a `route_for` method that allows calling another
direct route (or regular named route) which a set of arguments, e.g:

    resources :buckets

    direct :recordable do |recording|
      route_for(:bucket, recording.bucket)
    end

    direct :threadable do |threadable|
      route_for(:recordable, threadable.parent)
    end

This maintains the context of the original caller, e.g.

    threadable_path(threadable) # => /buckets/1
    threadable_url(threadable)  # => http://example.com/buckets/1

3 files changed, 20 insertions, 24 deletions

diff --git a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
index 984ded1ff5..e89ea8b21d 100644
--- a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
+++ b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
@@ -40,7 +40,7 @@ module ActionDispatch
     #
     # Example usage:
     #
-    #   edit_polymorphic_path(@post)              # => "/posts/1/edit"
+    #   edit_polymorphic_path(@post)           # => "/posts/1/edit"
     #   polymorphic_path(@post, format: :pdf)  # => "/posts/1.pdf"
     #
     # == Usage with mounted engines
@@ -104,7 +104,7 @@ module ActionDispatch
         end
 
         if mapping = polymorphic_mapping(record_or_hash_or_array)
-          return mapping.call(self, [record_or_hash_or_array, options])
+          return mapping.call(self, [record_or_hash_or_array, options], false)
         end
 
         opts   = options.dup
@@ -128,7 +128,7 @@ module ActionDispatch
         end
 
         if mapping = polymorphic_mapping(record_or_hash_or_array)
-          return mapping.call(self, [record_or_hash_or_array, options], only_path: true)
+          return mapping.call(self, [record_or_hash_or_array, options], true)
         end
 
         opts   = options.dup
@@ -273,7 +273,7 @@ module ActionDispatch
 
           def handle_model_call(target, record)
             if mapping = polymorphic_mapping(target, record)
-              mapping.call(target, [record], only_path: suffix == "path")
+              mapping.call(target, [record], suffix == "path")
             else
               method, args = handle_model(record)
               target.send(method, *args)
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 118dec2ad4..8a9a48938b 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -164,13 +164,13 @@ module ActionDispatch
 
           @path_helpers_module.module_eval do
             define_method(:"#{name}_path") do |*args|
-              helper.call(self, args, only_path: true)
+              helper.call(self, args, true)
             end
           end
 
           @url_helpers_module.module_eval do
             define_method(:"#{name}_url") do |*args|
-              helper.call(self, args)
+              helper.call(self, args, false)
             end
           end
         end
@@ -509,6 +509,10 @@ module ActionDispatch
               @_proxy.url_for(options)
             end
 
+            def route_for(name, *args)
+              @_proxy.route_for(name, *args)
+            end
+
             def optimize_routes_generation?
               @_proxy.optimize_routes_generation?
             end
@@ -613,26 +617,14 @@ module ActionDispatch
           @block = block
         end
 
-        def call(t, args, outer_options = {})
+        def call(t, args, only_path = false)
           options = args.extract_options!
-          url_options = eval_block(t, args, options)
-
-          case url_options
-          when String
-            t.url_for(url_options)
-          when Hash
-            t.url_for(url_options.merge(outer_options))
-          when ActionController::Parameters
-            if url_options.permitted?
-              t.url_for(url_options.to_h.merge(outer_options))
-            else
-              raise ArgumentError, "Generating a URL from non sanitized request parameters is insecure!"
-            end
-          when Array
-            opts = url_options.extract_options!
-            t.url_for(url_options.push(opts.merge(outer_options)))
+          url = t.url_for(eval_block(t, args, options))
+
+          if only_path
+            "/" + url.partition(%r{(?<!/)/(?!/)}).last
           else
-            t.url_for([url_options, outer_options])
+            url
           end
         end
 
diff --git a/actionpack/lib/action_dispatch/routing/url_for.rb b/actionpack/lib/action_dispatch/routing/url_for.rb
index 3e564f13d8..d199bece96 100644
--- a/actionpack/lib/action_dispatch/routing/url_for.rb
+++ b/actionpack/lib/action_dispatch/routing/url_for.rb
@@ -192,6 +192,10 @@ module ActionDispatch
         end
       end
 
+      def route_for(name, *args) # :nodoc:
+        public_send(:"#{name}_url", *args)
+      end
+
       protected
 
         def optimize_routes_generation?