7 files changed, 951 insertions, 813 deletions

diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index 48c10a7d4c..b91ffb8419 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -1,5 +1,5 @@
-require 'delegate'
-require 'active_support/core_ext/string/strip'
+require "delegate"
+require "active_support/core_ext/string/strip"
 
 module ActionDispatch
   module Routing
@@ -16,10 +16,6 @@ module ActionDispatch
         app.app
       end
 
-      def verb
-        super.source.gsub(/[$^]/, '')
-      end
-
       def path
         super.spec.to_s
       end
@@ -37,15 +33,15 @@ module ActionDispatch
       end
 
       def controller
-        requirements[:controller] || ':controller'
+        parts.include?(:controller) ? ":controller" : requirements[:controller]
       end
 
       def action
-        requirements[:action] || ':action'
+        parts.include?(:action) ? ":action" : requirements[:action]
       end
 
       def internal?
-        controller.to_s =~ %r{\Arails/(info|mailers|welcome)}
+        internal
       end
 
       def engine?
@@ -55,7 +51,7 @@ module ActionDispatch
 
     ##
     # This class is just used for displaying route information when someone
-    # executes `rake routes` or looks at the RoutingError page.
+    # executes `rails routes` or looks at the RoutingError page.
     # People should not use this class.
     class RoutesInspector # :nodoc:
       def initialize(routes)
@@ -64,12 +60,10 @@ module ActionDispatch
       end
 
       def format(formatter, filter = nil)
-        routes_to_display = filter_routes(filter)
-
+        routes_to_display = filter_routes(normalize_filter(filter))
         routes = collect_routes(routes_to_display)
-
         if routes.none?
-          formatter.no_routes
+          formatter.no_routes(collect_routes(@routes))
           return formatter.result
         end
 
@@ -86,37 +80,48 @@ module ActionDispatch
 
       private
 
-      def filter_routes(filter)
-        if filter
-          @routes.select { |route| route.defaults[:controller] == filter }
-        else
-          @routes
+        def normalize_filter(filter)
+          if filter.is_a?(Hash) && filter[:controller]
+            { controller: /#{filter[:controller].downcase.sub(/_?controller\z/, '').sub('::', '/')}/ }
+          elsif filter
+            { controller: /#{filter}/, action: /#{filter}/, verb: /#{filter}/, name: /#{filter}/, path: /#{filter}/ }
+          end
+        end
+
+        def filter_routes(filter)
+          if filter
+            @routes.select do |route|
+              route_wrapper = RouteWrapper.new(route)
+              filter.any? { |default, value| route_wrapper.send(default) =~ value }
+            end
+          else
+            @routes
+          end
         end
-      end
 
-      def collect_routes(routes)
-        routes.collect do |route|
-          RouteWrapper.new(route)
-        end.reject(&:internal?).collect do |route|
-          collect_engine_routes(route)
+        def collect_routes(routes)
+          routes.collect do |route|
+            RouteWrapper.new(route)
+          end.reject(&:internal?).collect do |route|
+            collect_engine_routes(route)
 
-          { name: route.name,
-            verb: route.verb,
-            path: route.path,
-            reqs: route.reqs }
+            { name: route.name,
+              verb: route.verb,
+              path: route.path,
+              reqs: route.reqs }
+          end
         end
-      end
 
-      def collect_engine_routes(route)
-        name = route.endpoint
-        return unless route.engine?
-        return if @engines[name]
+        def collect_engine_routes(route)
+          name = route.endpoint
+          return unless route.engine?
+          return if @engines[name]
 
-        routes = route.rack_app.routes
-        if routes.is_a?(ActionDispatch::Routing::RouteSet)
-          @engines[name] = collect_routes(routes.routes)
+          routes = route.rack_app.routes
+          if routes.is_a?(ActionDispatch::Routing::RouteSet)
+            @engines[name] = collect_routes(routes.routes)
+          end
         end
-      end
     end
 
     class ConsoleFormatter
@@ -140,19 +145,23 @@ module ActionDispatch
         @buffer << draw_header(routes)
       end
 
-      def no_routes
-        @buffer << <<-MESSAGE.strip_heredoc
+      def no_routes(routes)
+        @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
+        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 draw_section(routes)
-          header_lengths = ['Prefix', 'Verb', 'URI Pattern'].map(&:length)
+          header_lengths = ["Prefix", "Verb", "URI Pattern"].map(&:length)
           name_width, verb_width, path_width = widths(routes).zip(header_lengths).map(&:max)
 
           routes.map do |r|
@@ -191,7 +200,7 @@ 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>
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 15980db39b..4efde09b8b 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1,22 +1,21 @@
-require 'active_support/core_ext/hash/except'
-require 'active_support/core_ext/hash/reverse_merge'
-require 'active_support/core_ext/hash/slice'
-require 'active_support/core_ext/enumerable'
-require 'active_support/core_ext/array/extract_options'
-require 'active_support/core_ext/module/remove_method'
-require 'active_support/inflector'
-require 'action_dispatch/routing/redirection'
-require 'action_dispatch/routing/endpoint'
+require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/enumerable"
+require "active_support/core_ext/array/extract_options"
+require "action_dispatch/routing/redirection"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
     class Mapper
       URL_OPTIONS = [:protocol, :subdomain, :domain, :host, :port]
 
-      class Constraints < Endpoint #:nodoc:
+      class Constraints < Routing::Endpoint #:nodoc:
         attr_reader :app, :constraints
 
-        def initialize(app, constraints, dispatcher_p)
+        SERVE = ->(app, req) { app.serve req }
+        CALL  = ->(app, req) { app.call req.env }
+
+        def initialize(app, constraints, strategy)
           # Unwrap Constraints objects.  I don't actually think it's possible
           # to pass a Constraints object to this constructor, but there were
           # multiple places that kept testing children of this object.  I
@@ -26,12 +25,12 @@ module ActionDispatch
             app = app.app
           end
 
-          @dispatcher = dispatcher_p
+          @strategy = strategy
 
           @app, @constraints, = app, constraints
         end
 
-        def dispatcher?; @dispatcher; end
+        def dispatcher?; @strategy == SERVE; end
 
         def matches?(req)
           @constraints.all? do |constraint|
@@ -41,13 +40,9 @@ module ActionDispatch
         end
 
         def serve(req)
-          return [ 404, {'X-Cascade' => 'pass'}, [] ] unless matches?(req)
+          return [ 404, { "X-Cascade" => "pass" }, [] ] unless matches?(req)
 
-          if dispatcher?
-            @app.serve req
-          else
-            @app.call req.env
-          end
+          @strategy.call @app, req
         end
 
         private
@@ -59,101 +54,180 @@ module ActionDispatch
       class Mapping #:nodoc:
         ANCHOR_CHARACTERS_REGEX = %r{\A(\\A|\^)|(\\Z|\\z|\$)\Z}
 
-        attr_reader :requirements, :conditions, :defaults
-        attr_reader :to, :default_controller, :default_action, :as, :anchor
+        attr_reader :requirements, :defaults
+        attr_reader :to, :default_controller, :default_action
+        attr_reader :required_defaults, :ast
 
-        def self.build(scope, set, path, as, options)
+        def self.build(scope, set, ast, controller, default_action, to, via, formatted, options_constraints, anchor, options)
           options = scope[:options].merge(options) if scope[:options]
 
-          options.delete :only
-          options.delete :except
-          options.delete :shallow_path
-          options.delete :shallow_prefix
-          options.delete :shallow
+          defaults = (scope[:defaults] || {}).dup
+          scope_constraints = scope[:constraints] || {}
+
+          new set, ast, defaults, controller, default_action, scope[:module], to, formatted, scope_constraints, scope[:blocks] || [], via, options_constraints, anchor, options
+        end
+
+        def self.check_via(via)
+          if via.empty?
+            msg = "You should not use the `match` method in your router without specifying an HTTP method.\n" \
+              "If you want to expose your action to both GET and POST, add `via: [:get, :post]` option.\n" \
+              "If you want to expose your action to GET, use `get` in the router:\n" \
+              "  Instead of: match \"controller#action\"\n" \
+              "  Do: get \"controller#action\""
+            raise ArgumentError, msg
+          end
+          via
+        end
+
+        def self.normalize_path(path, format)
+          path = Mapper.normalize_path(path)
 
-          defaults = (scope[:defaults] || {}).merge options.delete(:defaults) || {}
+          if format == true
+            "#{path}.:format"
+          elsif optional_format?(path, format)
+            "#{path}(.:format)"
+          else
+            path
+          end
+        end
 
-          new scope, set, path, defaults, as, options
+        def self.optional_format?(path, format)
+          format != false && !path.include?(":format") && !path.end_with?("/")
         end
 
-        def initialize(scope, set, path, defaults, as, options)
-          @requirements, @conditions = {}, {}
+        def initialize(set, ast, defaults, controller, default_action, modyoule, to, formatted, scope_constraints, blocks, via, options_constraints, anchor, options)
           @defaults = defaults
           @set = set
 
-          @to                 = options.delete :to
-          @default_controller = options.delete(:controller) || scope[:controller]
-          @default_action     = options.delete(:action) || scope[:action]
-          @as                 = as
-          @anchor             = options.delete :anchor
+          @to                 = to
+          @default_controller = controller
+          @default_action     = default_action
+          @ast                = ast
+          @anchor             = anchor
+          @via                = via
+          @internal           = options.delete(:internal)
 
-          formatted = options.delete :format
-          via = Array(options.delete(:via) { [] })
-          options_constraints = options.delete :constraints
+          path_params = ast.find_all(&:symbol?).map(&:to_sym)
 
-          path = normalize_path! path, formatted
-          ast  = path_ast path
-          path_params = path_params ast
+          options = add_wildcard_options(options, formatted, ast)
 
-          options = normalize_options!(options, formatted, path_params, ast, scope[:module])
+          options = normalize_options!(options, path_params, modyoule)
 
+          split_options = constraints(options, path_params)
 
-          split_constraints(path_params, scope[:constraints]) if scope[:constraints]
-          constraints = constraints(options, path_params)
+          constraints = scope_constraints.merge Hash[split_options[:constraints] || []]
 
-          split_constraints path_params, constraints
+          if options_constraints.is_a?(Hash)
+            @defaults = Hash[options_constraints.find_all { |key, default|
+              URL_OPTIONS.include?(key) && (String === default || Integer === default)
+            }].merge @defaults
+            @blocks = blocks
+            constraints.merge! options_constraints
+          else
+            @blocks = blocks(options_constraints)
+          end
 
-          @blocks = blocks(options_constraints, scope[:blocks])
+          requirements, conditions = split_constraints path_params, constraints
+          verify_regexp_requirements requirements.map(&:last).grep(Regexp)
 
-          if options_constraints.is_a?(Hash)
-            split_constraints path_params, options_constraints
-            options_constraints.each do |key, default|
-              if URL_OPTIONS.include?(key) && (String === default || Fixnum === default)
-                @defaults[key] ||= default
-              end
-            end
+          formats = normalize_format(formatted)
+
+          @requirements = formats[:requirements].merge Hash[requirements]
+          @conditions = Hash[conditions]
+          @defaults = formats[:defaults].merge(@defaults).merge(normalize_defaults(options))
+
+          if path_params.include?(:action) && !@requirements.key?(:action)
+            @defaults[:action] ||= "index"
           end
 
-          normalize_format!(formatted)
+          @required_defaults = (split_options[:required_defaults] || []).map(&:first)
+        end
 
-          @conditions[:path_info] = path
-          @conditions[:parsed_path_info] = ast
+        def make_route(name, precedence)
+          route = Journey::Route.new(name,
+                            application,
+                            path,
+                            conditions,
+                            required_defaults,
+                            defaults,
+                            request_method,
+                            precedence,
+                            @internal)
+
+          route
+        end
 
-          add_request_method(via, @conditions)
-          normalize_defaults!(options)
+        def application
+          app(@blocks)
         end
 
-        def to_route
-          [ app(@blocks), conditions, requirements, defaults, as, anchor ]
+        def path
+          build_path @ast, requirements, @anchor
         end
 
-        private
+        def conditions
+          build_conditions @conditions, @set.request_class
+        end
 
-          def normalize_path!(path, format)
-            path = Mapper.normalize_path(path)
+        def build_conditions(current_conditions, request_class)
+          conditions = current_conditions.dup
 
-            if format == true
-              "#{path}.:format"
-            elsif optional_format?(path, format)
-              "#{path}(.:format)"
+          conditions.keep_if do |k, _|
+            request_class.public_method_defined?(k)
+          end
+        end
+        private :build_conditions
+
+        def request_method
+          @via.map { |x| Journey::Route.verb_matcher(x) }
+        end
+        private :request_method
+
+        JOINED_SEPARATORS = SEPARATORS.join # :nodoc:
+
+        def build_path(ast, requirements, anchor)
+          pattern = Journey::Path::Pattern.new(ast, requirements, JOINED_SEPARATORS, anchor)
+
+          # Find all the symbol nodes that are adjacent to literal nodes and alter
+          # the regexp so that Journey will partition them into custom routes.
+          ast.find_all { |node|
+            next unless node.cat?
+
+            if node.left.literal? && node.right.symbol?
+              symbol = node.right
+            elsif node.left.literal? && node.right.cat? && node.right.left.symbol?
+              symbol = node.right.left
+            elsif node.left.symbol? && node.right.literal?
+              symbol = node.left
+            elsif node.left.symbol? && node.right.cat? && node.right.left.literal?
+              symbol = node.left
             else
-              path
+              next
             end
-          end
 
-          def optional_format?(path, format)
-            format != false && !path.include?(':format') && !path.end_with?('/')
-          end
+            if symbol
+              symbol.regexp = /(?:#{Regexp.union(symbol.regexp, '-')})+/
+            end
+          }
+
+          pattern
+        end
+        private :build_path
 
-          def normalize_options!(options, formatted, path_params, path_ast, modyoule)
+        private
+          def add_wildcard_options(options, formatted, path_ast)
             # Add a constraint for wildcard route to make it non-greedy and match the
             # optional format part of the route by default
             if formatted != false
-              path_ast.grep(Journey::Nodes::Star) do |node|
-                options[node.name.to_sym] ||= /.+?/
-              end
+              path_ast.grep(Journey::Nodes::Star).each_with_object({}) { |node, hash|
+                hash[node.name.to_sym] ||= /.+?/
+              }.merge options
+            else
+              options
             end
+          end
 
+          def normalize_options!(options, path_params, modyoule)
             if path_params.include?(:controller)
               raise ArgumentError, ":controller segment is not allowed within a namespace block" if modyoule
 
@@ -178,74 +252,54 @@ module ActionDispatch
           end
 
           def split_constraints(path_params, constraints)
-            constraints.each_pair do |key, requirement|
-              if path_params.include?(key) || key == :controller
-                verify_regexp_requirement(requirement) if requirement.is_a?(Regexp)
-                @requirements[key] = requirement
-              else
-                @conditions[key] = requirement
-              end
-            end
-          end
-
-          def normalize_format!(formatted)
-            if formatted == true
-              @requirements[:format] ||= /.+/
-            elsif Regexp === formatted
-              @requirements[:format] = formatted
-              @defaults[:format] = nil
-            elsif String === formatted
-              @requirements[:format] = Regexp.compile(formatted)
-              @defaults[:format] = formatted
+            constraints.partition do |key, requirement|
+              path_params.include?(key) || key == :controller
             end
           end
 
-          def verify_regexp_requirement(requirement)
-            if requirement.source =~ ANCHOR_CHARACTERS_REGEX
-              raise ArgumentError, "Regexp anchor characters are not allowed in routing requirements: #{requirement.inspect}"
-            end
-
-            if requirement.multiline?
-              raise ArgumentError, "Regexp multiline option is not allowed in routing requirements: #{requirement.inspect}"
+          def normalize_format(formatted)
+            case formatted
+            when true
+              { requirements: { format: /.+/ },
+                defaults:     {} }
+            when Regexp
+              { requirements: { format: formatted },
+                defaults:     { format: nil } }
+            when String
+              { requirements: { format: Regexp.compile(formatted) },
+                defaults:     { format: formatted } }
+            else
+              { requirements: {}, defaults: {} }
             end
           end
 
-          def normalize_defaults!(options)
-            options.each_pair do |key, default|
-              unless Regexp === default
-                @defaults[key] = default
+          def verify_regexp_requirements(requirements)
+            requirements.each do |requirement|
+              if requirement.source =~ ANCHOR_CHARACTERS_REGEX
+                raise ArgumentError, "Regexp anchor characters are not allowed in routing requirements: #{requirement.inspect}"
               end
-            end
-          end
 
-          def verify_callable_constraint(callable_constraint)
-            unless callable_constraint.respond_to?(:call) || callable_constraint.respond_to?(:matches?)
-              raise ArgumentError, "Invalid constraint: #{callable_constraint.inspect} must respond to :call or :matches?"
+              if requirement.multiline?
+                raise ArgumentError, "Regexp multiline option is not allowed in routing requirements: #{requirement.inspect}"
+              end
             end
           end
 
-          def add_request_method(via, conditions)
-            return if via == [:all]
-
-            if via.empty?
-              msg = "You should not use the `match` method in your router without specifying an HTTP method.\n" \
-                    "If you want to expose your action to both GET and POST, add `via: [:get, :post]` option.\n" \
-                    "If you want to expose your action to GET, use `get` in the router:\n" \
-                    "  Instead of: match \"controller#action\"\n" \
-                    "  Do: get \"controller#action\""
-              raise ArgumentError, msg
-            end
-
-            conditions[:request_method] = via.map { |m| m.to_s.dasherize.upcase }
+          def normalize_defaults(options)
+            Hash[options.reject { |_, default| Regexp === default }]
           end
 
           def app(blocks)
-            if to.respond_to?(:call)
-              Constraints.new(to, blocks, false)
-            elsif blocks.any?
-              Constraints.new(dispatcher(defaults), blocks, true)
+            if to.is_a?(Class) && to < ActionController::Metal
+              Routing::RouteSet::StaticDispatcher.new to
             else
-              dispatcher(defaults)
+              if to.respond_to?(:call)
+                Constraints.new(to, blocks, Constraints::CALL)
+              elsif blocks.any?
+                Constraints.new(dispatcher(defaults.key?(:controller)), blocks, Constraints::SERVE)
+              else
+                dispatcher(defaults.key?(:controller))
+              end
             end
           end
 
@@ -278,7 +332,7 @@ module ActionDispatch
 
           def split_to(to)
             if to =~ /#/
-              to.split('#')
+              to.split("#")
             else
               []
             end
@@ -303,40 +357,29 @@ module ActionDispatch
             yield
           end
 
-          def blocks(options_constraints, scope_blocks)
-            if options_constraints && !options_constraints.is_a?(Hash)
-              verify_callable_constraint(options_constraints)
-              [options_constraints]
-            else
-              scope_blocks || []
+          def blocks(callable_constraint)
+            unless callable_constraint.respond_to?(:call) || callable_constraint.respond_to?(:matches?)
+              raise ArgumentError, "Invalid constraint: #{callable_constraint.inspect} must respond to :call or :matches?"
             end
+            [callable_constraint]
           end
 
           def constraints(options, path_params)
-            constraints = {}
-            required_defaults = []
-            options.each_pair do |key, option|
+            options.group_by do |key, option|
               if Regexp === option
-                constraints[key] = option
+                :constraints
               else
-                required_defaults << key unless path_params.include?(key)
+                if path_params.include?(key)
+                  :path_params
+                else
+                  :required_defaults
+                end
               end
             end
-            @conditions[:required_defaults] = required_defaults
-            constraints
-          end
-
-          def path_params(ast)
-            ast.grep(Journey::Nodes::Symbol).map { |n| n.name.to_sym }
-          end
-
-          def path_ast(path)
-            parser = Journey::Parser.new
-            parser.parse path
           end
 
-          def dispatcher(defaults)
-            @set.dispatcher defaults
+          def dispatcher(raise_on_name_error)
+            Routing::RouteSet::Dispatcher.new raise_on_name_error
           end
       end
 
@@ -354,23 +397,6 @@ module ActionDispatch
       end
 
       module Base
-        # You can specify what Rails should route "/" to with the root method:
-        #
-        #   root to: 'pages#main'
-        #
-        # For options, see +match+, as +root+ uses it internally.
-        #
-        # You can also pass a string which will expand
-        #
-        #   root 'pages#main'
-        #
-        # You should put the root route at the top of <tt>config/routes.rb</tt>,
-        # because this means it will be matched first. As this is the most popular route
-        # of most Rails applications, this is beneficial.
-        def root(options = {})
-          match '/', { :as => :root, :via => :get }.merge!(options)
-        end
-
         # Matches a url pattern to one or more routes.
         #
         # You should not use the +match+ method in your router
@@ -443,6 +469,21 @@ module ActionDispatch
         #   dynamic segment used to generate the routes).
         #   You can access that segment from your controller using
         #   <tt>params[<:param>]</tt>.
+        #   In your router:
+        #
+        #      resources :user, param: :name
+        #
+        #   You can override <tt>ActiveRecord::Base#to_param</tt> of a related
+        #   model to construct a URL:
+        #
+        #      class User < ActiveRecord::Base
+        #        def to_param
+        #          name
+        #        end
+        #      end
+        #
+        #   user = User.find_by(name: 'Phusion')
+        #   user_path(user)  # => "/users/Phusion"
         #
         # [:path]
         #   The path prefix for the routes.
@@ -526,7 +567,7 @@ module ActionDispatch
         # [:format]
         #   Allows you to specify the default value for optional +format+
         #   segment or disable it by supplying +false+.
-        def match(path, options=nil)
+        def match(path, options = nil)
         end
 
         # Mount a Rack-based application to be used within the application.
@@ -551,17 +592,20 @@ module ActionDispatch
         def mount(app, options = nil)
           if options
             path = options.delete(:at)
-          else
-            unless Hash === app
-              raise ArgumentError, "must be called with mount point"
-            end
-
+          elsif Hash === app
             options = app
             app, path = options.find { |k, _| k.respond_to?(:call) }
             options.delete(app) if app
           end
 
-          raise "A rack application must be specified" unless path
+          raise ArgumentError, "A rack application must be specified" unless app.respond_to?(:call)
+          raise ArgumentError, <<-MSG.strip_heredoc unless path
+            Must be called with mount point
+
+              mount SomeRackApp, at: "some_route"
+              or
+              mount(SomeRackApp => "some_route")
+          MSG
 
           rails_app = rails_app? app
           options[:as] ||= app_name(app, rails_app)
@@ -569,7 +613,7 @@ module ActionDispatch
           target_as       = name_for_action(options[:as], path)
           options[:via] ||= :all
 
-          match(path, options.merge(:to => app, :anchor => false, :format => false))
+          match(path, options.merge(to: app, anchor: false, format: false))
 
           define_generate_prefix(app, target_as) if rails_app
           self
@@ -588,7 +632,7 @@ module ActionDispatch
 
         # Query if the following named route was already defined.
         def has_named_route?(name)
-          @set.named_routes.routes[name.to_sym]
+          @set.named_routes.key? name
         end
 
         private
@@ -616,6 +660,7 @@ module ActionDispatch
                   super(options)
                 else
                   prefix_options = options.slice(*_route.segment_keys)
+                  prefix_options[:relative_url_root] = "".freeze
                   # we must actually delete prefix segment keys to avoid passing them to next url_for
                   _route.segment_keys.each { |k| options.delete(k) }
                   _routes.url_helpers.send("#{name}_path", prefix_options)
@@ -764,7 +809,7 @@ module ActionDispatch
           options = args.extract_options!.dup
           scope = {}
 
-          options[:path] = args.flatten.join('/') if args.any?
+          options[:path] = args.flatten.join("/") if args.any?
           options[:constraints] ||= {}
 
           unless nested_scope?
@@ -773,25 +818,34 @@ module ActionDispatch
           end
 
           if options[:constraints].is_a?(Hash)
-            defaults = options[:constraints].select do
-              |k, v| URL_OPTIONS.include?(k) && (v.is_a?(String) || v.is_a?(Fixnum))
+            defaults = options[:constraints].select do |k, v|
+              URL_OPTIONS.include?(k) && (v.is_a?(String) || v.is_a?(Integer))
             end
 
-            (options[:defaults] ||= {}).reverse_merge!(defaults)
+            options[:defaults] = defaults.merge(options[:defaults] || {})
           else
             block, options[:constraints] = options[:constraints], {}
           end
 
+          if options.key?(:only) || options.key?(:except)
+            scope[:action_options] = { only: options.delete(:only),
+                                       except: options.delete(:except) }
+          end
+
+          if options.key? :anchor
+            raise ArgumentError, "anchor is ignored unless passed to `match`"
+          end
+
           @scope.options.each do |option|
             if option == :blocks
               value = block
             elsif option == :options
               value = options
             else
-              value = options.delete(option)
+              value = options.delete(option) { POISON }
             end
 
-            if value
+            unless POISON == value
               scope[option] = send("merge_#{option}_scope", @scope[option], value)
             end
           end
@@ -803,14 +857,18 @@ module ActionDispatch
           @scope = @scope.parent
         end
 
+        POISON = Object.new # :nodoc:
+
         # Scopes routes to a specific controller
         #
         #   controller "food" do
         #     match "bacon", action: :bacon, via: :get
         #   end
-        def controller(controller, options={})
-          options[:controller] = controller
-          scope(options) { yield }
+        def controller(controller)
+          @scope = @scope.new(controller: controller)
+          yield
+        ensure
+          @scope = @scope.parent
         end
 
         # Scopes routes to a specific namespace. For example:
@@ -856,13 +914,14 @@ module ActionDispatch
 
           defaults = {
             module:         path,
-            path:           options.fetch(:path, path),
             as:             options.fetch(:as, path),
             shallow_path:   options.fetch(:path, path),
             shallow_prefix: options.fetch(:as, path)
           }
 
-          scope(defaults.merge!(options)) { yield }
+          path_scope(options.delete(:path) { path }) do
+            scope(defaults.merge!(options)) { yield }
+          end
         end
 
         # === Parameter Restriction
@@ -921,7 +980,7 @@ module ActionDispatch
         #      resources :iphones
         #    end
         def constraints(constraints = {})
-          scope(:constraints => constraints) { yield }
+          scope(constraints: constraints) { yield }
         end
 
         # Allows you to set default parameters for a route, such as this:
@@ -930,7 +989,10 @@ module ActionDispatch
         #   end
         # Using this, the +:id+ parameter here will default to 'home'.
         def defaults(defaults = {})
-          scope(:defaults => defaults) { yield }
+          @scope = @scope.new(defaults: merge_defaults_scope(@scope[:defaults], defaults))
+          yield
+        ensure
+          @scope = @scope.parent
         end
 
         private
@@ -962,6 +1024,14 @@ module ActionDispatch
             child
           end
 
+          def merge_via_scope(parent, child) #:nodoc:
+            child
+          end
+
+          def merge_format_scope(parent, child) #:nodoc:
+            child
+          end
+
           def merge_path_names_scope(parent, child) #:nodoc:
             merge_options_scope(parent, child)
           end
@@ -981,15 +1051,15 @@ module ActionDispatch
           end
 
           def merge_options_scope(parent, child) #:nodoc:
-            (parent || {}).except(*override_keys(child)).merge!(child)
+            (parent || {}).merge(child)
           end
 
           def merge_shallow_scope(parent, child) #:nodoc:
             child ? true : false
           end
 
-          def override_keys(child) #:nodoc:
-            child.key?(:only) || child.key?(:except) ? [:only, :except] : []
+          def merge_to_scope(parent, child)
+            child
           end
       end
 
@@ -1040,27 +1110,34 @@ module ActionDispatch
         CANONICAL_ACTIONS = %w(index create new show update destroy)
 
         class Resource #:nodoc:
-          attr_reader :controller, :path, :options, :param
+          attr_reader :controller, :path, :param
 
-          def initialize(entities, options = {})
+          def initialize(entities, api_only, shallow, options = {})
             @name       = entities.to_s
             @path       = (options[:path] || @name).to_s
             @controller = (options[:controller] || @name).to_s
             @as         = options[:as]
             @param      = (options[:param] || :id).to_sym
             @options    = options
-            @shallow    = false
+            @shallow    = shallow
+            @api_only   = api_only
+            @only       = options.delete :only
+            @except     = options.delete :except
           end
 
           def default_actions
-            [:index, :create, :new, :show, :update, :destroy, :edit]
+            if @api_only
+              [:index, :create, :show, :update, :destroy]
+            else
+              [:index, :create, :new, :show, :update, :destroy, :edit]
+            end
           end
 
           def actions
-            if only = @options[:only]
-              Array(only).map(&:to_sym)
-            elsif except = @options[:except]
-              default_actions - Array(except).map(&:to_sym)
+            if @only
+              Array(@only).map(&:to_sym)
+            elsif @except
+              default_actions - Array(@except).map(&:to_sym)
             else
               default_actions
             end
@@ -1087,7 +1164,7 @@ module ActionDispatch
           end
 
           def resource_scope
-            { :controller => controller }
+            controller
           end
 
           alias :collection_scope :path
@@ -1110,17 +1187,15 @@ module ActionDispatch
             "#{path}/:#{nested_param}"
           end
 
-          def shallow=(value)
-            @shallow = value
-          end
-
           def shallow?
             @shallow
           end
+
+          def singleton?; false; end
         end
 
         class SingletonResource < Resource #:nodoc:
-          def initialize(entities, options)
+          def initialize(entities, api_only, shallow, options)
             super
             @as         = nil
             @controller = (options[:controller] || plural).to_s
@@ -1128,7 +1203,11 @@ module ActionDispatch
           end
 
           def default_actions
-            [:show, :create, :update, :destroy, :new, :edit]
+            if @api_only
+              [:show, :create, :update, :destroy]
+            else
+              [:show, :create, :update, :destroy, :new, :edit]
+            end
           end
 
           def plural
@@ -1144,6 +1223,8 @@ module ActionDispatch
 
           alias :member_scope :path
           alias :nested_scope :path
+
+          def singleton?; true; end
         end
 
         def resources_path_names(options)
@@ -1163,11 +1244,11 @@ module ActionDispatch
         # the plural):
         #
         #   GET       /profile/new
-        #   POST      /profile
         #   GET       /profile
         #   GET       /profile/edit
         #   PATCH/PUT /profile
         #   DELETE    /profile
+        #   POST      /profile
         #
         # === Options
         # Takes same options as +resources+.
@@ -1178,20 +1259,23 @@ module ActionDispatch
             return self
           end
 
-          resource_scope(:resource, SingletonResource.new(resources.pop, options)) do
-            yield if block_given?
+          with_scope_level(:resource) do
+            options = apply_action_options options
+            resource_scope(SingletonResource.new(resources.pop, api_only?, @scope[:shallow], options)) do
+              yield if block_given?
 
-            concerns(options[:concerns]) if options[:concerns]
+              concerns(options[:concerns]) if options[:concerns]
 
-            collection do
-              post :create
-            end if parent_resource.actions.include?(:create)
+              new do
+                get :new
+              end if parent_resource.actions.include?(:new)
 
-            new do
-              get :new
-            end if parent_resource.actions.include?(:new)
+              set_member_mappings_for_resource
 
-            set_member_mappings_for_resource
+              collection do
+                post :create
+              end if parent_resource.actions.include?(:create)
+            end
           end
 
           self
@@ -1336,21 +1420,24 @@ module ActionDispatch
             return self
           end
 
-          resource_scope(:resources, Resource.new(resources.pop, options)) do
-            yield if block_given?
+          with_scope_level(:resources) do
+            options = apply_action_options options
+            resource_scope(Resource.new(resources.pop, api_only?, @scope[:shallow], options)) do
+              yield if block_given?
 
-            concerns(options[:concerns]) if options[:concerns]
+              concerns(options[:concerns]) if options[:concerns]
 
-            collection do
-              get  :index if parent_resource.actions.include?(:index)
-              post :create if parent_resource.actions.include?(:create)
-            end
+              collection do
+                get  :index if parent_resource.actions.include?(:index)
+                post :create if parent_resource.actions.include?(:create)
+              end
 
-            new do
-              get :new
-            end if parent_resource.actions.include?(:new)
+              new do
+                get :new
+              end if parent_resource.actions.include?(:new)
 
-            set_member_mappings_for_resource
+              set_member_mappings_for_resource
+            end
           end
 
           self
@@ -1374,7 +1461,7 @@ module ActionDispatch
           end
 
           with_scope_level(:collection) do
-            scope(parent_resource.collection_scope) do
+            path_scope(parent_resource.collection_scope) do
               yield
             end
           end
@@ -1398,9 +1485,11 @@ module ActionDispatch
 
           with_scope_level(:member) do
             if shallow?
-              shallow_scope(parent_resource.member_scope) { yield }
+              shallow_scope {
+                path_scope(parent_resource.member_scope) { yield }
+              }
             else
-              scope(parent_resource.member_scope) { yield }
+              path_scope(parent_resource.member_scope) { yield }
             end
           end
         end
@@ -1411,7 +1500,7 @@ module ActionDispatch
           end
 
           with_scope_level(:new) do
-            scope(parent_resource.new_scope(action_path(:new))) do
+            path_scope(parent_resource.new_scope(action_path(:new))) do
               yield
             end
           end
@@ -1424,9 +1513,15 @@ module ActionDispatch
 
           with_scope_level(:nested) do
             if shallow? && shallow_nesting_depth >= 1
-              shallow_scope(parent_resource.nested_scope, nested_options) { yield }
+              shallow_scope do
+                path_scope(parent_resource.nested_scope) do
+                  scope(nested_options) { yield }
+                end
+              end
             else
-              scope(parent_resource.nested_scope, nested_options) { yield }
+              path_scope(parent_resource.nested_scope) do
+                scope(nested_options) { yield }
+              end
             end
           end
         end
@@ -1441,13 +1536,14 @@ module ActionDispatch
         end
 
         def shallow
-          scope(:shallow => true) do
-            yield
-          end
+          @scope = @scope.new(shallow: true)
+          yield
+        ensure
+          @scope = @scope.parent
         end
 
         def shallow?
-          parent_resource.instance_of?(Resource) && @scope[:shallow]
+          !parent_resource.singleton? && @scope[:shallow]
         end
 
         # Matches a url pattern to one or more routes.
@@ -1456,11 +1552,13 @@ module ActionDispatch
         #   match 'path' => 'controller#action', via: patch
         #   match 'path', to: 'controller#action', via: :post
         #   match 'path', 'otherpath', on: :member, via: :get
-        def match(path, *rest)
+        def match(path, *rest, &block)
           if rest.empty? && Hash === path
             options  = path
             path, to = options.find { |name, _value| name.is_a?(String) }
 
+            raise ArgumentError, "Route path not specified" if path.nil?
+
             case to
             when Symbol
               options[:action] = to
@@ -1481,77 +1579,30 @@ module ActionDispatch
             paths = [path] + rest
           end
 
-          options[:anchor] = true unless options.key?(:anchor)
-
-          if options[:on] && !VALID_ON_OPTIONS.include?(options[:on])
-            raise ArgumentError, "Unknown scope #{on.inspect} given to :on"
-          end
-
-          if @scope[:controller] && @scope[:action]
-            options[:to] ||= "#{@scope[:controller]}##{@scope[:action]}"
-          end
-
-          paths.each do |_path|
-            route_options = options.dup
-            route_options[:path] ||= _path if _path.is_a?(String)
-
-            path_without_format = _path.to_s.sub(/\(\.:format\)$/, '')
-            if using_match_shorthand?(path_without_format, route_options)
-              route_options[:to] ||= path_without_format.gsub(%r{^/}, "").sub(%r{/([^/]*)$}, '#\1')
-              route_options[:to].tr!("-", "_")
-            end
-
-            decomposed_match(_path, route_options)
-          end
-          self
-        end
-
-        def using_match_shorthand?(path, options)
-          path && (options[:to] || options[:action]).nil? && path =~ %r{^/?[-\w]+/[-\w/]+$}
-        end
-
-        def decomposed_match(path, options) # :nodoc:
-          if on = options.delete(:on)
-            send(on) { decomposed_match(path, options) }
+          if options.key?(:defaults)
+            defaults(options.delete(:defaults)) { map_match(paths, options, &block) }
           else
-            case @scope.scope_level
-            when :resources
-              nested { decomposed_match(path, options) }
-            when :resource
-              member { decomposed_match(path, options) }
-            else
-              add_route(path, options)
-            end
+            map_match(paths, options, &block)
           end
         end
 
-        def add_route(action, options) # :nodoc:
-          path = path_for_action(action, options.delete(:path))
-          raise ArgumentError, "path is required" if path.blank?
-
-          action = action.to_s.dup
-
-          if action =~ /^[\w\-\/]+$/
-            options[:action] ||= action.tr('-', '_') unless action.include?("/")
-          else
-            action = nil
-          end
-
-          as = if !options.fetch(:as, true) # if it's set to nil or false
-                 options.delete(:as)
-               else
-                 name_for_action(options.delete(:as), action)
-               end
-
-          mapping = Mapping.build(@scope, @set, URI.parser.escape(path), as, options)
-          app, conditions, requirements, defaults, as, anchor = mapping.to_route
-          @set.add_route(app, conditions, requirements, defaults, as, anchor)
-        end
-
-        def root(path, options={})
+        # You can specify what Rails should route "/" to with the root method:
+        #
+        #   root to: 'pages#main'
+        #
+        # For options, see +match+, as +root+ uses it internally.
+        #
+        # You can also pass a string which will expand
+        #
+        #   root 'pages#main'
+        #
+        # You should put the root route at the top of <tt>config/routes.rb</tt>,
+        # because this means it will be matched first. As this is the most popular route
+        # of most Rails applications, this is beneficial.
+        def root(path, options = {})
           if path.is_a?(String)
             options[:to] = path
-          elsif path.is_a?(Hash) and options.empty?
+          elsif path.is_a?(Hash) && options.empty?
             options = path
           else
             raise ArgumentError, "must be called with a path and/or options"
@@ -1559,12 +1610,12 @@ module ActionDispatch
 
           if @scope.resources?
             with_scope_level(:root) do
-              scope(parent_resource.path) do
-                super(options)
+              path_scope(parent_resource.path) do
+                match_root_route(options)
               end
             end
           else
-            super(options)
+            match_root_route(options)
           end
         end
 
@@ -1604,23 +1655,20 @@ module ActionDispatch
               return true
             end
 
-            unless action_options?(options)
-              options.merge!(scope_action_options) if scope_action_options?
-            end
-
             false
           end
 
-          def action_options?(options) #:nodoc:
-            options[:only] || options[:except]
+          def apply_action_options(options) # :nodoc:
+            return options if action_options? options
+            options.merge scope_action_options
           end
 
-          def scope_action_options? #:nodoc:
-            @scope[:options] && (@scope[:options][:only] || @scope[:options][:except])
+          def action_options?(options) #:nodoc:
+            options[:only] || options[:except]
           end
 
           def scope_action_options #:nodoc:
-            @scope[:options].slice(:only, :except)
+            @scope[:action_options] || {}
           end
 
           def resource_scope? #:nodoc:
@@ -1635,18 +1683,6 @@ module ActionDispatch
             @scope.nested?
           end
 
-          def with_exclusive_scope
-            begin
-              @scope = @scope.new(:as => nil, :path => nil)
-
-              with_scope_level(:exclusive) do
-                yield
-              end
-            ensure
-              @scope = @scope.parent
-            end
-          end
-
           def with_scope_level(kind)
             @scope = @scope.new_level(kind)
             yield
@@ -1654,21 +1690,16 @@ module ActionDispatch
             @scope = @scope.parent
           end
 
-          def resource_scope(kind, resource) #:nodoc:
-            resource.shallow = @scope[:shallow]
-            @scope = @scope.new(:scope_level_resource => resource)
-            @nesting.push(resource)
+          def resource_scope(resource) #:nodoc:
+            @scope = @scope.new(scope_level_resource: resource)
 
-            with_scope_level(kind) do
-              scope(parent_resource.resource_scope) { yield }
-            end
+            controller(resource.resource_scope) { yield }
           ensure
-            @nesting.pop
             @scope = @scope.parent
           end
 
           def nested_options #:nodoc:
-            options = { :as => parent_resource.member_name }
+            options = { as: parent_resource.member_name }
             options[:constraints] = {
               parent_resource.nested_param => param_constraint
             } if param_constraint?
@@ -1676,12 +1707,10 @@ module ActionDispatch
             options
           end
 
-          def nesting_depth #:nodoc:
-            @nesting.size
-          end
-
           def shallow_nesting_depth #:nodoc:
-            @nesting.count(&:shallow?)
+            @scope.find_all { |node|
+              node.frame[:scope_level_resource]
+            }.count { |node| node.frame[:scope_level_resource].shallow? }
           end
 
           def param_constraint? #:nodoc:
@@ -1696,27 +1725,28 @@ module ActionDispatch
             resource_method_scope? && CANONICAL_ACTIONS.include?(action.to_s)
           end
 
-          def shallow_scope(path, options = {}) #:nodoc:
-            scope = { :as   => @scope[:shallow_prefix],
-                      :path => @scope[:shallow_path] }
+          def shallow_scope #:nodoc:
+            scope = { as: @scope[:shallow_prefix],
+                      path: @scope[:shallow_path] }
             @scope = @scope.new scope
 
-            scope(path, options) { yield }
+            yield
           ensure
             @scope = @scope.parent
           end
 
           def path_for_action(action, path) #:nodoc:
-            if path.blank? && canonical_action?(action)
+            return "#{@scope[:path]}/#{path}" if path
+
+            if canonical_action?(action)
               @scope[:path].to_s
             else
-              "#{@scope[:path]}/#{action_path(action, path)}"
+              "#{@scope[:path]}/#{action_path(action)}"
             end
           end
 
-          def action_path(name, path = nil) #:nodoc:
-            name = name.to_sym if name.is_a?(String)
-            path || @scope[:path_names][name] || name.to_s
+          def action_path(name) #:nodoc:
+            @scope[:path_names][name.to_sym] || name
           end
 
           def prefix_name_for_action(as, action) #:nodoc:
@@ -1726,8 +1756,8 @@ module ActionDispatch
               prefix = action
             end
 
-            if prefix && prefix != '/' && !prefix.empty?
-              Mapper.normalize_name prefix.to_s.tr('-', '_')
+            if prefix && prefix != "/" && !prefix.empty?
+              Mapper.normalize_name prefix.to_s.tr("-", "_")
             end
           end
 
@@ -1743,14 +1773,14 @@ module ActionDispatch
             end
 
             action_name = @scope.action_name(name_prefix, prefix, collection_name, member_name)
-            candidate = action_name.select(&:present?).join('_')
+            candidate = action_name.select(&:present?).join("_")
 
             unless candidate.empty?
               # If a name was not explicitly given, we check if it is valid
               # and return nil in case it isn't. Otherwise, we pass the invalid name
               # forward so the underlying router engine treats it and raises an exception.
               if as.nil?
-                candidate unless candidate !~ /\A[_a-z]/i || @set.named_routes.key?(candidate)
+                candidate unless candidate !~ /\A[_a-z]/i || has_named_route?(candidate)
               else
                 candidate
               end
@@ -1768,6 +1798,124 @@ module ActionDispatch
               delete :destroy if parent_resource.actions.include?(:destroy)
             end
           end
+
+          def api_only?
+            @set.api_only?
+          end
+
+        private
+
+          def path_scope(path)
+            @scope = @scope.new(path: merge_path_scope(@scope[:path], path))
+            yield
+          ensure
+            @scope = @scope.parent
+          end
+
+          def map_match(paths, options)
+            if options[:on] && !VALID_ON_OPTIONS.include?(options[:on])
+              raise ArgumentError, "Unknown scope #{on.inspect} given to :on"
+            end
+
+            if @scope[:to]
+              options[:to] ||= @scope[:to]
+            end
+
+            if @scope[:controller] && @scope[:action]
+              options[:to] ||= "#{@scope[:controller]}##{@scope[:action]}"
+            end
+
+            controller = options.delete(:controller) || @scope[:controller]
+            option_path = options.delete :path
+            to = options.delete :to
+            via = Mapping.check_via Array(options.delete(:via) {
+              @scope[:via]
+            })
+            formatted = options.delete(:format) { @scope[:format] }
+            anchor = options.delete(:anchor) { true }
+            options_constraints = options.delete(:constraints) || {}
+
+            path_types = paths.group_by(&:class)
+            path_types.fetch(String, []).each do |_path|
+              route_options = options.dup
+              if _path && option_path
+                raise ArgumentError, "Ambigous route definition. Both :path and the route path where specified as strings."
+              end
+              to = get_to_from_path(_path, to, route_options[:action])
+              decomposed_match(_path, controller, route_options, _path, to, via, formatted, anchor, options_constraints)
+            end
+
+            path_types.fetch(Symbol, []).each do |action|
+              route_options = options.dup
+              decomposed_match(action, controller, route_options, option_path, to, via, formatted, anchor, options_constraints)
+            end
+
+            self
+          end
+
+          def get_to_from_path(path, to, action)
+            return to if to || action
+
+            path_without_format = path.sub(/\(\.:format\)$/, "")
+            if using_match_shorthand?(path_without_format)
+              path_without_format.gsub(%r{^/}, "").sub(%r{/([^/]*)$}, '#\1').tr("-", "_")
+            else
+              nil
+            end
+          end
+
+          def using_match_shorthand?(path)
+            path =~ %r{^/?[-\w]+/[-\w/]+$}
+          end
+
+          def decomposed_match(path, controller, options, _path, to, via, formatted, anchor, options_constraints) # :nodoc:
+            if on = options.delete(:on)
+              send(on) { decomposed_match(path, controller, options, _path, to, via, formatted, anchor, options_constraints) }
+            else
+              case @scope.scope_level
+              when :resources
+                nested { decomposed_match(path, controller, options, _path, to, via, formatted, anchor, options_constraints) }
+              when :resource
+                member { decomposed_match(path, controller, options, _path, to, via, formatted, anchor, options_constraints) }
+              else
+                add_route(path, controller, options, _path, to, via, formatted, anchor, options_constraints)
+              end
+            end
+          end
+
+          def add_route(action, controller, options, _path, to, via, formatted, anchor, options_constraints) # :nodoc:
+            path = path_for_action(action, _path)
+            raise ArgumentError, "path is required" if path.blank?
+
+            action = action.to_s
+
+            default_action = options.delete(:action) || @scope[:action]
+
+            if action =~ /^[\w\-\/]+$/
+              default_action ||= action.tr("-", "_") unless action.include?("/")
+            else
+              action = nil
+            end
+
+            as = if !options.fetch(:as, true) # if it's set to nil or false
+              options.delete(:as)
+            else
+              name_for_action(options.delete(:as), action)
+            end
+
+            path = Mapping.normalize_path URI.parser.escape(path), formatted
+            ast = Journey::Parser.parse path
+
+            mapping = Mapping.build(@scope, @set, ast, controller, default_action, to, via, formatted, options_constraints, anchor, options)
+            @set.add_route(mapping, ast, as, anchor)
+          end
+
+          def match_root_route(options)
+            name = has_named_route?(name_for_action(:root, nil)) ? nil : :root
+            args = ["/", { as: name, via: :get }.merge!(options)]
+
+            match(*args)
+          end
       end
 
       # Routing Concerns allow you to declare common routes that can be reused
@@ -1878,14 +2026,14 @@ module ActionDispatch
       class Scope # :nodoc:
         OPTIONS = [:path, :shallow_path, :as, :shallow_prefix, :module,
                    :controller, :action, :path_names, :constraints,
-                   :shallow, :blocks, :defaults, :options]
+                   :shallow, :blocks, :defaults, :via, :format, :options, :to]
 
         RESOURCE_SCOPES = [:resource, :resources]
         RESOURCE_METHOD_SCOPES = [:collection, :member, :new]
 
         attr_reader :parent, :scope_level
 
-        def initialize(hash, parent = {}, scope_level = nil)
+        def initialize(hash, parent = NULL, scope_level = nil)
           @hash = hash
           @parent = parent
           @scope_level = scope_level
@@ -1933,27 +2081,33 @@ module ActionDispatch
         end
 
         def new_level(level)
-          self.class.new(self, self, level)
-        end
-
-        def fetch(key, &block)
-          @hash.fetch(key, &block)
+          self.class.new(frame, self, level)
         end
 
         def [](key)
-          @hash.fetch(key) { @parent[key] }
+          scope = find { |node| node.frame.key? key }
+          scope && scope.frame[key]
         end
 
-        def []=(k,v)
-          @hash[k] = v
+        include Enumerable
+
+        def each
+          node = self
+          until node.equal? NULL
+            yield node
+            node = node.parent
+          end
         end
+
+        def frame; @hash; end
+
+        NULL = Scope.new(nil, nil)
       end
 
       def initialize(set) #:nodoc:
         @set = set
-        @scope = Scope.new({ :path_names => @set.resources_path_names })
+        @scope = Scope.new(path_names: @set.resources_path_names)
         @concerns = {}
-        @nesting = []
       end
 
       include Base
diff --git a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
index 9934f5547a..432b9bf4c1 100644
--- a/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
+++ b/actionpack/lib/action_dispatch/routing/polymorphic_routes.rb
@@ -4,7 +4,7 @@ module ActionDispatch
     # given an Active Record model instance. They are to be used in combination with
     # ActionController::Resources.
     #
-    # These methods are useful when you want to generate correct URL or path to a RESTful
+    # These methods are useful when you want to generate the correct URL or path to a RESTful
     # resource without having to know the exact type of the record in question.
     #
     # Nested resources and/or namespaces are also supported, as illustrated in the example:
@@ -79,7 +79,7 @@ module ActionDispatch
       #   polymorphic_url([blog, post], anchor: 'my_anchor', script_name: "/my_app")
       #     # => "http://example.com/my_app/blogs/1/posts/1#my_anchor"
       #
-      # For all of these options, see the documentation for <tt>url_for</tt>.
+      # For all of these options, see the documentation for {url_for}[rdoc-ref:ActionDispatch::Routing::UrlFor].
       #
       # ==== Functionality
       #
@@ -134,7 +134,6 @@ module ActionDispatch
                                                opts
       end
 
-
       %w(edit new).each do |action|
         module_eval <<-EOT, __FILE__, __LINE__ + 1
           def #{action}_polymorphic_url(record_or_hash, options = {})
@@ -149,176 +148,175 @@ module ActionDispatch
 
       private
 
-      def polymorphic_url_for_action(action, record_or_hash, options)
-        polymorphic_url(record_or_hash, options.merge(:action => action))
-      end
+        def polymorphic_url_for_action(action, record_or_hash, options)
+          polymorphic_url(record_or_hash, options.merge(action: action))
+        end
 
-      def polymorphic_path_for_action(action, record_or_hash, options)
-        polymorphic_path(record_or_hash, options.merge(:action => action))
-      end
+        def polymorphic_path_for_action(action, record_or_hash, options)
+          polymorphic_path(record_or_hash, options.merge(action: action))
+        end
 
-      class HelperMethodBuilder # :nodoc:
-        CACHE = { 'path' => {}, 'url' => {} }
+        class HelperMethodBuilder # :nodoc:
+          CACHE = { "path" => {}, "url" => {} }
 
-        def self.get(action, type)
-          type   = type.to_s
-          CACHE[type].fetch(action) { build action, type }
-        end
+          def self.get(action, type)
+            type = type.to_s
+            CACHE[type].fetch(action) { build action, type }
+          end
 
-        def self.url;  CACHE['url'.freeze][nil]; end
-        def self.path; CACHE['path'.freeze][nil]; end
+          def self.url;  CACHE["url".freeze][nil]; end
+          def self.path; CACHE["path".freeze][nil]; end
 
-        def self.build(action, type)
-          prefix = action ? "#{action}_" : ""
-          suffix = type
-          if action.to_s == 'new'
-            HelperMethodBuilder.singular prefix, suffix
-          else
-            HelperMethodBuilder.plural prefix, suffix
+          def self.build(action, type)
+            prefix = action ? "#{action}_" : ""
+            suffix = type
+            if action.to_s == "new"
+              HelperMethodBuilder.singular prefix, suffix
+            else
+              HelperMethodBuilder.plural prefix, suffix
+            end
           end
-        end
 
-        def self.singular(prefix, suffix)
-          new(->(name) { name.singular_route_key }, prefix, suffix)
-        end
+          def self.singular(prefix, suffix)
+            new(->(name) { name.singular_route_key }, prefix, suffix)
+          end
 
-        def self.plural(prefix, suffix)
-          new(->(name) { name.route_key }, prefix, suffix)
-        end
+          def self.plural(prefix, suffix)
+            new(->(name) { name.route_key }, prefix, suffix)
+          end
 
-        def self.polymorphic_method(recipient, record_or_hash_or_array, action, type, options)
-          builder = get action, type
+          def self.polymorphic_method(recipient, record_or_hash_or_array, action, type, options)
+            builder = get action, type
+
+            case record_or_hash_or_array
+            when Array
+              record_or_hash_or_array = record_or_hash_or_array.compact
+              if record_or_hash_or_array.empty?
+                raise ArgumentError, "Nil location provided. Can't build URI."
+              end
+              if record_or_hash_or_array.first.is_a?(ActionDispatch::Routing::RoutesProxy)
+                recipient = record_or_hash_or_array.shift
+              end
+
+              method, args = builder.handle_list record_or_hash_or_array
+            when String, Symbol
+              method, args = builder.handle_string record_or_hash_or_array
+            when Class
+              method, args = builder.handle_class record_or_hash_or_array
 
-          case record_or_hash_or_array
-          when Array
-            record_or_hash_or_array = record_or_hash_or_array.compact
-            if record_or_hash_or_array.empty?
+            when nil
               raise ArgumentError, "Nil location provided. Can't build URI."
+            else
+              method, args = builder.handle_model record_or_hash_or_array
             end
-            if record_or_hash_or_array.first.is_a?(ActionDispatch::Routing::RoutesProxy)
-              recipient = record_or_hash_or_array.shift
-            end
-
-            method, args = builder.handle_list record_or_hash_or_array
-          when String, Symbol
-            method, args = builder.handle_string record_or_hash_or_array
-          when Class
-            method, args = builder.handle_class record_or_hash_or_array
 
-          when nil
-            raise ArgumentError, "Nil location provided. Can't build URI."
-          else
-            method, args = builder.handle_model record_or_hash_or_array
+            if options.empty?
+              recipient.send(method, *args)
+            else
+              recipient.send(method, *args, options)
+            end
           end
 
+          attr_reader :suffix, :prefix
 
-          if options.empty?
-            recipient.send(method, *args)
-          else
-            recipient.send(method, *args, options)
+          def initialize(key_strategy, prefix, suffix)
+            @key_strategy = key_strategy
+            @prefix       = prefix
+            @suffix       = suffix
           end
-        end
-
-        attr_reader :suffix, :prefix
-
-        def initialize(key_strategy, prefix, suffix)
-          @key_strategy = key_strategy
-          @prefix       = prefix
-          @suffix       = suffix
-        end
-
-        def handle_string(record)
-          [get_method_for_string(record), []]
-        end
-
-        def handle_string_call(target, str)
-          target.send get_method_for_string str
-        end
 
-        def handle_class(klass)
-          [get_method_for_class(klass), []]
-        end
+          def handle_string(record)
+            [get_method_for_string(record), []]
+          end
 
-        def handle_class_call(target, klass)
-          target.send get_method_for_class klass
-        end
+          def handle_string_call(target, str)
+            target.send get_method_for_string str
+          end
 
-        def handle_model(record)
-          args  = []
+          def handle_class(klass)
+            [get_method_for_class(klass), []]
+          end
 
-          model = record.to_model
-          named_route = if model.persisted?
-                          args << model
-                          get_method_for_string model.model_name.singular_route_key
-                        else
-                          get_method_for_class model
-                        end
+          def handle_class_call(target, klass)
+            target.send get_method_for_class klass
+          end
 
-          [named_route, args]
-        end
+          def handle_model(record)
+            args  = []
 
-        def handle_model_call(target, model)
-          method, args = handle_model model
-          target.send(method, *args)
-        end
+            model = record.to_model
+            named_route = if model.persisted?
+              args << model
+              get_method_for_string model.model_name.singular_route_key
+            else
+              get_method_for_class model
+            end
 
-        def handle_list(list)
-          record_list = list.dup
-          record      = record_list.pop
+            [named_route, args]
+          end
 
-          args = []
+          def handle_model_call(target, model)
+            method, args = handle_model model
+            target.send(method, *args)
+          end
 
-          route  = record_list.map { |parent|
-            case parent
+          def handle_list(list)
+            record_list = list.dup
+            record      = record_list.pop
+
+            args = []
+
+            route = record_list.map { |parent|
+              case parent
+              when Symbol, String
+                parent.to_s
+              when Class
+                args << parent
+                parent.model_name.singular_route_key
+              else
+                args << parent.to_model
+                parent.to_model.model_name.singular_route_key
+              end
+            }
+
+            route <<
+            case record
             when Symbol, String
-              parent.to_s
+              record.to_s
             when Class
-              args << parent
-              parent.model_name.singular_route_key
+              @key_strategy.call record.model_name
             else
-              args << parent.to_model
-              parent.to_model.model_name.singular_route_key
+              model = record.to_model
+              if model.persisted?
+                args << model
+                model.model_name.singular_route_key
+              else
+                @key_strategy.call model.model_name
+              end
             end
-          }
-
-          route <<
-          case record
-          when Symbol, String
-            record.to_s
-          when Class
-            @key_strategy.call record.model_name
-          else
-            model = record.to_model
-            if model.persisted?
-              args << model
-              model.model_name.singular_route_key
-            else
-              @key_strategy.call model.model_name
-            end
-          end
 
-          route << suffix
+            route << suffix
 
-          named_route = prefix + route.join("_")
-          [named_route, args]
-        end
+            named_route = prefix + route.join("_")
+            [named_route, args]
+          end
 
-        private
+          private
 
-        def get_method_for_class(klass)
-          name   = @key_strategy.call klass.model_name
-          get_method_for_string name
-        end
+            def get_method_for_class(klass)
+              name = @key_strategy.call klass.model_name
+              get_method_for_string name
+            end
 
-        def get_method_for_string(str)
-          "#{prefix}#{str}_#{suffix}"
-        end
+            def get_method_for_string(str)
+              "#{prefix}#{str}_#{suffix}"
+            end
 
-        [nil, 'new', 'edit'].each do |action|
-          CACHE['url'][action]  = build action, 'url'
-          CACHE['path'][action] = build action, 'path'
+            [nil, "new", "edit"].each do |action|
+              CACHE["url"][action]  = build action, "url"
+              CACHE["path"][action] = build action, "path"
+            end
         end
-      end
     end
   end
 end
diff --git a/actionpack/lib/action_dispatch/routing/redirection.rb b/actionpack/lib/action_dispatch/routing/redirection.rb
index 3c1c4fadf6..4e2318a45e 100644
--- a/actionpack/lib/action_dispatch/routing/redirection.rb
+++ b/actionpack/lib/action_dispatch/routing/redirection.rb
@@ -1,9 +1,9 @@
-require 'action_dispatch/http/request'
-require 'active_support/core_ext/uri'
-require 'active_support/core_ext/array/extract_options'
-require 'rack/utils'
-require 'action_controller/metal/exceptions'
-require 'action_dispatch/routing/endpoint'
+require "action_dispatch/http/request"
+require "active_support/core_ext/uri"
+require "active_support/core_ext/array/extract_options"
+require "rack/utils"
+require "action_controller/metal/exceptions"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -22,9 +22,8 @@ module ActionDispatch
       end
 
       def serve(req)
-        req.check_path_parameters!
         uri = URI.parse(path(req.path_parameters, req))
-        
+
         unless uri.host
           if relative_path?(uri.path)
             uri.path = "#{req.script_name}/#{uri.path}"
@@ -32,7 +31,7 @@ module ActionDispatch
             uri.path = req.script_name.empty? ? "/" : req.script_name
           end
         end
-          
+
         uri.scheme ||= req.scheme
         uri.host   ||= req.host
         uri.port   ||= req.port unless req.standard_port?
@@ -40,9 +39,9 @@ module ActionDispatch
         body = %(<html><body>You are being <a href="#{ERB::Util.unwrapped_html_escape(uri.to_s)}">redirected</a>.</body></html>)
 
         headers = {
-          'Location' => uri.to_s,
-          'Content-Type' => 'text/html',
-          'Content-Length' => body.length.to_s
+          "Location" => uri.to_s,
+          "Content-Type" => "text/html",
+          "Content-Length" => body.length.to_s
         }
 
         [ status, headers, [body] ]
@@ -58,19 +57,19 @@ module ActionDispatch
 
       private
         def relative_path?(path)
-          path && !path.empty? && path[0] != '/'
+          path && !path.empty? && path[0] != "/"
         end
 
         def escape(params)
-          Hash[params.map{ |k,v| [k, Rack::Utils.escape(v)] }]
+          Hash[params.map { |k, v| [k, Rack::Utils.escape(v)] }]
         end
 
         def escape_fragment(params)
-          Hash[params.map{ |k,v| [k, Journey::Router::Utils.escape_fragment(v)] }]
+          Hash[params.map { |k, v| [k, Journey::Router::Utils.escape_fragment(v)] }]
         end
 
         def escape_path(params)
-          Hash[params.map{ |k,v| [k, Journey::Router::Utils.escape_path(v)] }]
+          Hash[params.map { |k, v| [k, Journey::Router::Utils.escape_path(v)] }]
         end
     end
 
@@ -104,11 +103,11 @@ module ActionDispatch
 
       def path(params, request)
         url_options = {
-          :protocol => request.protocol,
-          :host     => request.host,
-          :port     => request.optional_port,
-          :path     => request.path,
-          :params   => request.query_parameters
+          protocol: request.protocol,
+          host: request.host,
+          port: request.optional_port,
+          path: request.path,
+          params: request.query_parameters
         }.merge! options
 
         if !params.empty? && url_options[:path].match(/%\{\w*\}/)
@@ -124,17 +123,16 @@ module ActionDispatch
             url_options[:script_name] = request.script_name
           end
         end
-        
+
         ActionDispatch::Http::URL.url_for url_options
       end
 
       def inspect
-        "redirect(#{status}, #{options.map{ |k,v| "#{k}: #{v}" }.join(', ')})"
+        "redirect(#{status}, #{options.map { |k, v| "#{k}: #{v}" }.join(', ')})"
       end
     end
 
     module Redirection
-
       # Redirect any path to another path:
       #
       #   get "/stories" => redirect("/posts")
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index d0d8ded515..5853adb110 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -1,14 +1,11 @@
-require 'action_dispatch/journey'
-require 'forwardable'
-require 'thread_safe'
-require 'active_support/concern'
-require 'active_support/core_ext/object/to_query'
-require 'active_support/core_ext/hash/slice'
-require 'active_support/core_ext/module/remove_method'
-require 'active_support/core_ext/array/extract_options'
-require 'action_controller/metal/exceptions'
-require 'action_dispatch/http/request'
-require 'action_dispatch/routing/endpoint'
+require "action_dispatch/journey"
+require "active_support/core_ext/object/to_query"
+require "active_support/core_ext/hash/slice"
+require "active_support/core_ext/module/remove_method"
+require "active_support/core_ext/array/extract_options"
+require "action_controller/metal/exceptions"
+require "action_dispatch/http/request"
+require "action_dispatch/routing/endpoint"
 
 module ActionDispatch
   module Routing
@@ -21,65 +18,47 @@ module ActionDispatch
       alias inspect to_s
 
       class Dispatcher < Routing::Endpoint
-        def initialize(defaults)
-          @defaults = defaults
-          @controller_class_names = ThreadSafe::Cache.new
+        def initialize(raise_on_name_error)
+          @raise_on_name_error = raise_on_name_error
         end
 
         def dispatcher?; true; end
 
         def serve(req)
-          req.check_path_parameters!
-          params = req.path_parameters
-
-          prepare_params!(params)
-
-          # Just raise undefined constant errors if a controller was specified as default.
-          unless controller = controller(params, @defaults.key?(:controller))
-            return [404, {'X-Cascade' => 'pass'}, []]
+          params     = req.path_parameters
+          controller = controller req
+          res        = controller.make_response! req
+          dispatch(controller, params[:action], req, res)
+        rescue ActionController::RoutingError
+          if @raise_on_name_error
+            raise
+          else
+            return [404, { "X-Cascade" => "pass" }, []]
           end
-
-          dispatch(controller, params[:action], req.env)
         end
 
-        def prepare_params!(params)
-          normalize_controller!(params)
-          merge_default_action!(params)
-        end
+      private
 
-        # If this is a default_controller (i.e. a controller specified by the user)
-        # we should raise an error in case it's not found, because it usually means
-        # a user error. However, if the controller was retrieved through a dynamic
-        # segment, as in :controller(/:action), we should simply return nil and
-        # delegate the control back to Rack cascade. Besides, if this is not a default
-        # controller, it means we should respect the @scope[:module] parameter.
-        def controller(params, default_controller=true)
-          if params && params.key?(:controller)
-            controller_param = params[:controller]
-            controller_reference(controller_param)
-          end
+        def controller(req)
+          req.controller_class
         rescue NameError => e
-          raise ActionController::RoutingError, e.message, e.backtrace if default_controller
+          raise ActionController::RoutingError, e.message, e.backtrace
         end
 
-      private
-
-        def controller_reference(controller_param)
-          const_name = @controller_class_names[controller_param] ||= "#{controller_param.camelize}Controller"
-          ActiveSupport::Dependencies.constantize(const_name)
+        def dispatch(controller, action, req, res)
+          controller.dispatch(action, req, res)
         end
+      end
 
-        def dispatch(controller, action, env)
-          controller.action(action).call(env)
+      class StaticDispatcher < Dispatcher
+        def initialize(controller_class)
+          super(false)
+          @controller_class = controller_class
         end
 
-        def normalize_controller!(params)
-          params[:controller] = params[:controller].underscore if params.key?(:controller)
-        end
+        private
 
-        def merge_default_action!(params)
-          params[:action] ||= 'index'
-        end
+          def controller(_); @controller_class; end
       end
 
       # A NamedRouteCollection instance is a collection of named routes, and also
@@ -88,9 +67,10 @@ module ActionDispatch
       class NamedRouteCollection
         include Enumerable
         attr_reader :routes, :url_helpers_module, :path_helpers_module
+        private :routes
 
         def initialize
-          @routes  = {}
+          @routes = {}
           @path_helpers = Set.new
           @url_helpers = Set.new
           @url_helpers_module  = Module.new
@@ -142,6 +122,7 @@ module ActionDispatch
         end
 
         def key?(name)
+          return unless name
           routes.key? name.to_sym
         end
 
@@ -198,40 +179,40 @@ module ActionDispatch
 
             private
 
-            def optimized_helper(args)
-              params = parameterize_args(args) { |k|
-                raise_generation_error(args)
-              }
+              def optimized_helper(args)
+                params = parameterize_args(args) do
+                  raise_generation_error(args)
+                end
 
-              @route.format params
-            end
+                @route.format params
+              end
 
-            def optimize_routes_generation?(t)
-              t.send(:optimize_routes_generation?)
-            end
+              def optimize_routes_generation?(t)
+                t.send(:optimize_routes_generation?)
+              end
 
-            def parameterize_args(args)
-              params = {}
-              @arg_size.times { |i|
-                key = @required_parts[i]
-                value = args[i].to_param
-                yield key if value.nil? || value.empty?
-                params[key] = value
-              }
-              params
-            end
+              def parameterize_args(args)
+                params = {}
+                @arg_size.times { |i|
+                  key = @required_parts[i]
+                  value = args[i].to_param
+                  yield key if value.nil? || value.empty?
+                  params[key] = value
+                }
+                params
+              end
 
-            def raise_generation_error(args)
-              missing_keys = []
-              params = parameterize_args(args) { |missing_key|
-                missing_keys << missing_key
-              }
-              constraints = Hash[@route.requirements.merge(params).sort_by{|k,v| k.to_s}]
-              message = "No route matches #{constraints.inspect}"
-              message << " missing required keys: #{missing_keys.sort.inspect}"
+              def raise_generation_error(args)
+                missing_keys = []
+                params = parameterize_args(args) { |missing_key|
+                  missing_keys << missing_key
+                }
+                constraints = Hash[@route.requirements.merge(params).sort_by { |k, v| k.to_s }]
+                message = "No route matches #{constraints.inspect}"
+                message << ", missing required keys: #{missing_keys.sort.inspect}"
 
-              raise ActionController::UrlGenerationError, message
-            end
+                raise ActionController::UrlGenerationError, message
+              end
           end
 
           def initialize(route, options, route_name, url_strategy)
@@ -267,9 +248,13 @@ module ActionDispatch
                 path_params -= controller_options.keys
                 path_params -= result.keys
               end
-              path_params -= inner_options.keys
-              path_params.take(args.size).each do |param|
-                result[param] = args.shift
+              inner_options.each_key do |key|
+                path_params.delete(key)
+              end
+
+              args.each_with_index do |arg, index|
+                param = path_params[index]
+                result[param] = arg if param
               end
             end
 
@@ -278,29 +263,39 @@ module ActionDispatch
         end
 
         private
-        # Create a url helper allowing ordered parameters to be associated
-        # with corresponding dynamic segments, so you can do:
-        #
-        #   foo_url(bar, baz, bang)
-        #
-        # Instead of:
-        #
-        #   foo_url(bar: bar, baz: baz, bang: bang)
-        #
-        # Also allow options hash, so you can do:
-        #
-        #   foo_url(bar, baz, bang, sort_by: 'baz')
-        #
-        def define_url_helper(mod, route, name, opts, route_key, url_strategy)
-          helper = UrlHelper.create(route, opts, route_key, url_strategy)
-          mod.module_eval do
-            define_method(name) do |*args|
-              options = nil
-              options = args.pop if args.last.is_a? Hash
-              helper.call self, args, options
+          # Create a url helper allowing ordered parameters to be associated
+          # with corresponding dynamic segments, so you can do:
+          #
+          #   foo_url(bar, baz, bang)
+          #
+          # Instead of:
+          #
+          #   foo_url(bar: bar, baz: baz, bang: bang)
+          #
+          # Also allow options hash, so you can do:
+          #
+          #   foo_url(bar, baz, bang, sort_by: 'baz')
+          #
+          def define_url_helper(mod, route, name, opts, route_key, url_strategy)
+            helper = UrlHelper.create(route, opts, route_key, url_strategy)
+            mod.module_eval do
+              define_method(name) do |*args|
+                last = args.last
+                options = \
+                  case last
+                  when Hash
+                    args.pop
+                  when ActionController::Parameters
+                    if last.permitted?
+                      args.pop.to_h
+                    else
+                      raise ArgumentError, ActionDispatch::Routing::INSECURE_URL_PARAMETERS_MESSAGE
+                    end
+                  end
+                helper.call self, args, options
+              end
             end
           end
-        end
       end
 
       # strategy for building urls to send to the client
@@ -315,21 +310,27 @@ module ActionDispatch
       alias :routes :set
 
       def self.default_resources_path_names
-        { :new => 'new', :edit => 'edit' }
+        { new: "new", edit: "edit" }
       end
 
       def self.new_with_config(config)
+        route_set_config = DEFAULT_CONFIG
+
+        # engines apparently don't have this set
         if config.respond_to? :relative_url_root
-          new Config.new config.relative_url_root
-        else
-          # engines apparently don't have this set
-          new
+          route_set_config.relative_url_root = config.relative_url_root
+        end
+
+        if config.respond_to? :api_only
+          route_set_config.api_only = config.api_only
         end
+
+        new route_set_config
       end
 
-      Config = Struct.new :relative_url_root
+      Config = Struct.new :relative_url_root, :api_only
 
-      DEFAULT_CONFIG = Config.new(nil)
+      DEFAULT_CONFIG = Config.new(nil, false)
 
       def initialize(config = DEFAULT_CONFIG)
         self.named_routes = NamedRouteCollection.new
@@ -345,17 +346,26 @@ module ActionDispatch
 
         @set    = Journey::Routes.new
         @router = Journey::Router.new @set
-        @formatter = Journey::Formatter.new @set
+        @formatter = Journey::Formatter.new self
       end
 
       def relative_url_root
         @config.relative_url_root
       end
 
+      def api_only?
+        @config.api_only
+      end
+
       def request_class
         ActionDispatch::Request
       end
 
+      def make_request(env)
+        request_class.new env
+      end
+      private :make_request
+
       def draw(&block)
         clear! unless @disable_clear_and_finalize
         eval_block(block)
@@ -372,10 +382,6 @@ module ActionDispatch
       end
 
       def eval_block(block)
-        if block.arity == 1
-          raise "You are using the old router DSL which has been removed in Rails 3.1. " <<
-            "Please check how to update your routes file at: http://www.engineyard.com/blog/2010/the-lowdown-on-routes-in-rails-3/"
-        end
         mapper = Mapper.new(self)
         if default_scope
           mapper.with_default_scope(default_scope, &block)
@@ -399,10 +405,6 @@ module ActionDispatch
         @prepend.each { |blk| eval_block(blk) }
       end
 
-      def dispatcher(defaults)
-        Routing::RouteSet::Dispatcher.new(defaults)
-      end
-
       module MountedHelpers
         extend ActiveSupport::Concern
         include UrlFor
@@ -498,7 +500,7 @@ module ActionDispatch
         routes.empty?
       end
 
-      def add_route(app, conditions = {}, requirements = {}, defaults = {}, name = nil, anchor = true)
+      def add_route(mapping, path_ast, name, anchor)
         raise ArgumentError, "Invalid route name: '#{name}'" unless name.blank? || name.to_s.match(/^[_a-z]\w*$/i)
 
         if name && named_routes[name]
@@ -509,74 +511,32 @@ module ActionDispatch
             "http://guides.rubyonrails.org/routing.html#restricting-the-routes-created"
         end
 
-        path = conditions.delete :path_info
-        ast  = conditions.delete :parsed_path_info
-        path = build_path(path, ast, requirements, anchor)
-        conditions = build_conditions(conditions, path.names.map(&:to_sym))
-
-        route = @set.add_route(app, path, conditions, defaults, name)
+        route = @set.add_route(name, mapping)
         named_routes[name] = route if name
-        route
-      end
-
-      def build_path(path, ast, requirements, anchor)
-        strexp = Journey::Router::Strexp.new(
-            ast,
-            path,
-            requirements,
-            SEPARATORS,
-            anchor)
-
-        pattern = Journey::Path::Pattern.new(strexp)
-
-        builder = Journey::GTG::Builder.new pattern.spec
-
-        # Get all the symbol nodes followed by literals that are not the
-        # dummy node.
-        symbols = pattern.spec.grep(Journey::Nodes::Symbol).find_all { |n|
-          builder.followpos(n).first.literal?
-        }
-
-        # Get all the symbol nodes preceded by literals.
-        symbols.concat pattern.spec.find_all(&:literal?).map { |n|
-          builder.followpos(n).first
-        }.find_all(&:symbol?)
-
-        symbols.each { |x|
-          x.regexp = /(?:#{Regexp.union(x.regexp, '-')})+/
-        }
 
-        pattern
-      end
-      private :build_path
-
-      def build_conditions(current_conditions, path_values)
-        conditions = current_conditions.dup
-
-        # Rack-Mount requires that :request_method be a regular expression.
-        # :request_method represents the HTTP verb that matches this route.
-        #
-        # Here we munge values before they get sent on to rack-mount.
-        verbs = conditions[:request_method] || []
-        unless verbs.empty?
-          conditions[:request_method] = %r[^#{verbs.join('|')}$]
+        if route.segment_keys.include?(:controller)
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :controller segment in a route is deprecated and
+            will be removed in Rails 5.1.
+          MSG
         end
 
-        conditions.keep_if do |k, _|
-          k == :action || k == :controller || k == :required_defaults ||
-            request_class.public_method_defined?(k) || path_values.include?(k)
+        if route.segment_keys.include?(:action)
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :action segment in a route is deprecated and
+            will be removed in Rails 5.1.
+          MSG
         end
+
+        route
       end
-      private :build_conditions
 
       class Generator
         PARAMETERIZE = lambda do |name, value|
           if name == :controller
             value
-          elsif value.is_a?(Array)
-            value.map(&:to_param).join('/')
-          elsif param = value.to_param
-            param
+          else
+            value.to_param
           end
         end
 
@@ -584,16 +544,14 @@ module ActionDispatch
 
         def initialize(named_route, options, recall, set)
           @named_route = named_route
-          @options     = options.dup
-          @recall      = recall.dup
+          @options     = options
+          @recall      = recall
           @set         = set
 
-          normalize_recall!
           normalize_options!
           normalize_controller_action_id!
           use_relative_controller!
           normalize_controller!
-          normalize_action!
         end
 
         def controller
@@ -607,16 +565,11 @@ module ActionDispatch
         def use_recall_for(key)
           if @recall[key] && (!@options.key?(key) || @options[key] == @recall[key])
             if !named_route_exists? || segment_keys.include?(key)
-              @options[key] = @recall.delete(key)
+              @options[key] = @recall[key]
             end
           end
         end
 
-        # Set 'index' as default action for recall
-        def normalize_recall!
-          @recall[:action] ||= 'index'
-        end
-
         def normalize_options!
           # If an explicit :controller was given, always make :action explicit
           # too, so that action expiry works as expected for things like
@@ -628,12 +581,12 @@ module ActionDispatch
           # be "index", not the recalled action of "show".
 
           if options[:controller]
-            options[:action]     ||= 'index'
+            options[:action]     ||= "index"
             options[:controller]   = options[:controller].to_s
           end
 
           if options.key?(:action)
-            options[:action] = (options[:action] || 'index').to_s
+            options[:action] = (options[:action] || "index").to_s
           end
         end
 
@@ -643,8 +596,8 @@ module ActionDispatch
         # :controller, :action or :id is not found, don't pull any
         # more keys from the recall.
         def normalize_controller_action_id!
-          use_recall_for(:controller) or return
-          use_recall_for(:action) or return
+          use_recall_for(:controller) || return
+          use_recall_for(:action) || return
           use_recall_for(:id)
         end
 
@@ -652,7 +605,7 @@ module ActionDispatch
         # is specified, the controller becomes "foo/baz/bat"
         def use_relative_controller!
           if !named_route && different_controller? && !controller.start_with?("/")
-            old_parts = current_controller.split('/')
+            old_parts = current_controller.split("/")
             size = controller.count("/") + 1
             parts = old_parts[0...-size] << controller
             @options[:controller] = parts.join("/")
@@ -661,13 +614,12 @@ module ActionDispatch
 
         # Remove leading slashes from controllers
         def normalize_controller!
-          @options[:controller] = controller.sub(%r{^/}, '') if controller
-        end
-
-        # Move 'index' action from options to recall
-        def normalize_action!
-          if @options[:action] == 'index'
-            @recall[:action] = @options.delete(:action)
+          if controller
+            if controller.start_with?("/".freeze)
+              @options[:controller] = controller[1..-1]
+            else
+              @options[:controller] = controller
+            end
           end
         end
 
@@ -694,11 +646,11 @@ module ActionDispatch
 
       # Generate the path indicated by the arguments, and return an array of
       # the keys that were not used to generate it.
-      def extra_keys(options, recall={})
+      def extra_keys(options, recall = {})
         generate_extras(options, recall).last
       end
 
-      def generate_extras(options, recall={})
+      def generate_extras(options, recall = {})
         route_key = options.delete :use_route
         path, params = generate(route_key, options, recall)
         return path, params.keys
@@ -711,14 +663,18 @@ module ActionDispatch
 
       RESERVED_OPTIONS = [:host, :protocol, :port, :subdomain, :domain, :tld_length,
                           :trailing_slash, :anchor, :params, :only_path, :script_name,
-                          :original_script_name]
+                          :original_script_name, :relative_url_root]
 
       def optimize_routes_generation?
         default_url_options.empty?
       end
 
       def find_script_name(options)
-        options.delete(:script_name) || relative_url_root || ''
+        options.delete(:script_name) || find_relative_url_root(options) || ""
+      end
+
+      def find_relative_url_root(options)
+        options.delete(:relative_url_root) || relative_url_root
       end
 
       def path_for(options, route_name = nil)
@@ -736,7 +692,7 @@ module ActionDispatch
           password = options.delete :password
         end
 
-        recall  = options.delete(:_recall) { {} }
+        recall = options.delete(:_recall) { {} }
 
         original_script_name = options.delete(:original_script_name)
         script_name = find_script_name options
@@ -764,7 +720,7 @@ module ActionDispatch
       end
 
       def call(env)
-        req = request_class.new(env)
+        req = make_request(env)
         req.path_info = Journey::Router::Utils.normalize_path(req.path_info)
         @router.serve(req)
       end
@@ -775,12 +731,12 @@ module ActionDispatch
         extras = environment[:extras] || {}
 
         begin
-          env = Rack::MockRequest.env_for(path, {:method => method})
+          env = Rack::MockRequest.env_for(path, method: method)
         rescue URI::InvalidURIError => e
           raise ActionController::RoutingError, e.message
         end
 
-        req = request_class.new(env)
+        req = make_request(env)
         @router.recognize(req) do |route, params|
           params.merge!(extras)
           params.each do |key, value|
@@ -793,14 +749,13 @@ module ActionDispatch
           req.path_parameters = old_params.merge params
           app = route.app
           if app.matches?(req) && app.dispatcher?
-            dispatcher = app.app
-
-            if dispatcher.controller(params, false)
-              dispatcher.prepare_params!(params)
-              return params
-            else
+            begin
+              req.controller_class
+            rescue NameError
               raise ActionController::RoutingError, "A route matches #{path.inspect}, but references missing controller: #{params[:controller].camelize}Controller"
             end
+
+            return req.path_parameters
           end
         end
 
diff --git a/actionpack/lib/action_dispatch/routing/routes_proxy.rb b/actionpack/lib/action_dispatch/routing/routes_proxy.rb
index 040ea04046..ee847eaeed 100644
--- a/actionpack/lib/action_dispatch/routing/routes_proxy.rb
+++ b/actionpack/lib/action_dispatch/routing/routes_proxy.rb
@@ -1,4 +1,4 @@
-require 'active_support/core_ext/array/extract_options'
+require "active_support/core_ext/array/extract_options"
 
 module ActionDispatch
   module Routing
@@ -19,7 +19,7 @@ module ActionDispatch
         end
       end
 
-      def respond_to?(method, include_private = false)
+      def respond_to_missing?(method, include_private = false)
         super || @helpers.respond_to?(method)
       end
 
diff --git a/actionpack/lib/action_dispatch/routing/url_for.rb b/actionpack/lib/action_dispatch/routing/url_for.rb
index eb554ec383..a1ac5a2b6c 100644
--- a/actionpack/lib/action_dispatch/routing/url_for.rb
+++ b/actionpack/lib/action_dispatch/routing/url_for.rb
@@ -1,7 +1,7 @@
 module ActionDispatch
   module Routing
     # In <tt>config/routes.rb</tt> you define URL-to-controller mappings, but the reverse
-    # is also possible: an URL can be generated from one of your routing definitions.
+    # is also possible: a URL can be generated from one of your routing definitions.
     # URL generation functionality is centralized in this module.
     #
     # See ActionDispatch::Routing for general information about routing and routes.rb.
@@ -52,9 +52,11 @@ module ActionDispatch
     # argument.
     #
     # For convenience reasons, mailers provide a shortcut for ActionController::UrlFor#url_for.
-    # So within mailers, you only have to type 'url_for' instead of 'ActionController::UrlFor#url_for'
-    # in full. However, mailers don't have hostname information, and that's why you'll still
-    # have to specify the <tt>:host</tt> argument when generating URLs in mailers.
+    # So within mailers, you only have to type +url_for+ instead of 'ActionController::UrlFor#url_for'
+    # in full. However, mailers don't have hostname information, and you still have to provide
+    # the +:host+ argument or set the default host that will be used in all mailers using the
+    # configuration option +config.action_mailer.default_url_options+. For more information on
+    # url_for in mailers read the ActionMailer#Base documentation.
     #
     #
     # == URL generation for named routes
@@ -147,6 +149,20 @@ module ActionDispatch
       #    # => 'http://somehost.org/myapp/tasks/testing'
       #    url_for controller: 'tasks', action: 'testing', host: 'somehost.org', script_name: "/myapp", only_path: true
       #    # => '/myapp/tasks/testing'
+      #
+      # Missing routes keys may be filled in from the current request's parameters
+      # (e.g. +:controller+, +:action+, +:id+ and any other parameters that are
+      # placed in the path). Given that the current action has been reached
+      # through `GET /users/1`:
+      #
+      #   url_for(only_path: true)                        # => '/users/1'
+      #   url_for(only_path: true, action: 'edit')        # => '/users/1/edit'
+      #   url_for(only_path: true, action: 'edit', id: 2) # => '/users/2/edit'
+      #
+      # Notice that no +:id+ parameter was provided to the first +url_for+ call
+      # and the helper used the one from the route's path. Any path parameter
+      # implicitly used by +url_for+ can always be overwritten like shown on the
+      # last +url_for+ calls.
       def url_for(options = nil)
         case options
         when nil
@@ -155,12 +171,20 @@ module ActionDispatch
           route_name = options.delete :use_route
           _routes.url_for(options.symbolize_keys.reverse_merge!(url_options),
                          route_name)
+        when ActionController::Parameters
+          unless options.permitted?
+            raise ArgumentError.new(ActionDispatch::Routing::INSECURE_URL_PARAMETERS_MESSAGE)
+          end
+          route_name = options.delete :use_route
+          _routes.url_for(options.to_h.symbolize_keys.
+                          reverse_merge!(url_options), route_name)
         when String
           options
         when Symbol
           HelperMethodBuilder.url.handle_string_call self, options
         when Array
-          polymorphic_url(options, options.extract_options!)
+          components = options.dup
+          polymorphic_url(components, components.extract_options!)
         when Class
           HelperMethodBuilder.url.handle_class_call self, options
         else
@@ -170,20 +194,20 @@ module ActionDispatch
 
       protected
 
-      def optimize_routes_generation?
-        _routes.optimize_routes_generation? && default_url_options.empty?
-      end
+        def optimize_routes_generation?
+          _routes.optimize_routes_generation? && default_url_options.empty?
+        end
 
-      def _with_routes(routes)
-        old_routes, @_routes = @_routes, routes
-        yield
-      ensure
-        @_routes = old_routes
-      end
+        def _with_routes(routes)
+          old_routes, @_routes = @_routes, routes
+          yield
+        ensure
+          @_routes = old_routes
+        end
 
-      def _routes_context
-        self
-      end
+        def _routes_context
+          self
+        end
     end
   end
 end