Defer route drawing to the first request, or when url_helpers called

Executes the first routes reload when the route set is first used to
serve a request, generate a url, or otherwise. Previously, this was
executed unconditionally on boot, which can slow down boot time
unnecessarily for larger apps with lots of routes.

Author: gmcgibbon

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -351,7 +351,7 @@ def define_url_helper(mod, name, helper, url_strategy)
       PATH    = ->(options) { ActionDispatch::Http::URL.path_for(options) }
       UNKNOWN = ->(options) { ActionDispatch::Http::URL.url_for(options) }
 
-      attr_accessor :formatter, :set, :named_routes, :default_scope, :router
+      attr_accessor :formatter, :set, :named_routes, :router
       attr_accessor :disable_clear_and_finalize, :resources_path_names
       attr_accessor :default_url_options, :draw_paths
       attr_reader :env_key, :polymorphic_mappings
@@ -363,7 +363,7 @@ def self.default_resources_path_names
       end
 
       def self.new_with_config(config)
-        route_set_config = DEFAULT_CONFIG
+        route_set_config = DEFAULT_CONFIG.dup
 
         # engines apparently don't have this set
         if config.respond_to? :relative_url_root
@@ -374,14 +374,18 @@ def self.new_with_config(config)
           route_set_config.api_only = config.api_only
         end
 
+        if config.respond_to? :default_scope
+          route_set_config.default_scope = config.default_scope
+        end
+
         new route_set_config
       end
 
-      Config = Struct.new :relative_url_root, :api_only
+      Config = Struct.new :relative_url_root, :api_only, :default_scope
 
-      DEFAULT_CONFIG = Config.new(nil, false)
+      DEFAULT_CONFIG = Config.new(nil, false, nil)
 
-      def initialize(config = DEFAULT_CONFIG)
+      def initialize(config = DEFAULT_CONFIG.dup)
         self.named_routes = NamedRouteCollection.new
         self.resources_path_names = self.class.default_resources_path_names
         self.default_url_options = {}
@@ -416,6 +420,14 @@ def api_only?
         @config.api_only
       end
 
+      def default_scope
+        @config.default_scope
+      end
+
+      def default_scope=(new_default_scope)
+        @config.default_scope = new_default_scope
+      end
+
       def request_class
         ActionDispatch::Request
       end

actionpack/test/abstract_unit.rb

@@ -34,6 +34,8 @@ def env
       @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "test")
     end
 
+    def application; end
+
     def root; end
   end
 end

actionpack/test/dispatch/routing_assertions_test.rb

@@ -4,7 +4,11 @@
 require "rails/engine"
 require "controller/fake_controllers"
 
-class SecureArticlesController < ArticlesController; end
+class SecureArticlesController < ArticlesController
+  def index
+    render(inline: "")
+  end
+end
 class BlockArticlesController < ArticlesController; end
 class QueryArticlesController < ArticlesController; end
 
@@ -276,6 +280,20 @@ class RoutingAssertionsControllerTest < ActionController::TestCase
 
   class WithRoutingTest < ActionController::TestCase
     include RoutingAssertionsSharedTests::WithRoutingSharedTests
+
+    test "with_routing routes are reachable" do
+      @controller = SecureArticlesController.new
+
+      with_routing do |routes|
+        routes.draw do
+          get :new_route, to: "secure_articles#index"
+        end
+
+        get :index
+
+        assert_predicate(response, :ok?)
+      end
+    end
   end
 end
 
@@ -295,6 +313,18 @@ class RoutingAssertionsIntegrationTest < ActionDispatch::IntegrationTest
 
   class WithRoutingTest < ActionDispatch::IntegrationTest
     include RoutingAssertionsSharedTests::WithRoutingSharedTests
+
+    test "with_routing routes are reachable" do
+      with_routing do |routes|
+        routes.draw do
+          get :new_route, to: "secure_articles#index"
+        end
+
+        get "/new_route"
+
+        assert_predicate(response, :ok?)
+      end
+    end
   end
 
   class WithRoutingSettingsTest < ActionDispatch::IntegrationTest

railties/CHANGELOG.md

@@ -1,3 +1,15 @@
+*   Defer route drawing to the first request, or when url_helpers are called
+
+    Executes the first routes reload in middleware, or when a route set's
+    url_helpers receives a route call / asked if it responds to a route.
+    Previously, this was executed unconditionally on boot, which can
+    slow down boot time unnecessarily for larger apps with lots of routes.
+
+    Environments like production that have `config.eager_load = true` will
+    continue to eagerly load routes on boot.
+
+    *Gannon McGibbon*
+
 *   Generate form helpers to use `textarea*` methods instead of `text_area*` methods
 
     *Sean Doyle*

railties/lib/rails/application.rb

@@ -9,6 +9,7 @@
 require "active_support/encrypted_configuration"
 require "active_support/hash_with_indifferent_access"
 require "active_support/configuration_file"
+require "active_support/parameter_filter"
 require "rails/engine"
 require "rails/autoloaders"
 
@@ -153,6 +154,10 @@ def reload_routes!
       routes_reloader.reload!
     end
 
+    def reload_routes_unless_loaded # :nodoc:
+      initialized? && routes_reloader.execute_unless_loaded
+    end
+
     # Returns a key generator (ActiveSupport::CachingKeyGenerator) for a
     # specified +secret_key_base+. The return value is memoized, so additional
     # calls with the same +secret_key_base+ will return the same key generator

railties/lib/rails/application/finisher.rb

@@ -160,7 +160,6 @@ def self.complete(_state)
       initializer :set_routes_reloader_hook do |app|
         reloader = routes_reloader
         reloader.eager_load = app.config.eager_load
-        reloader.execute
         reloaders << reloader
 
         app.reloader.to_run do
@@ -178,7 +177,7 @@ def self.complete(_state)
           ActiveSupport.run_load_hooks(:after_routes_loaded, self)
         end
 
-        ActiveSupport.run_load_hooks(:after_routes_loaded, self)
+        reloader.execute_unless_loaded if !app.routes.is_a?(Engine::LazyRouteSet) || app.config.eager_load
       end
 
       # Set clearing dependencies after the finisher hook to ensure paths

railties/lib/rails/application/routes_reloader.rb

@@ -7,7 +7,7 @@ class Application
     class RoutesReloader
       include ActiveSupport::Callbacks
 
-      attr_reader :route_sets, :paths, :external_routes
+      attr_reader :route_sets, :paths, :external_routes, :loaded
       attr_accessor :eager_load
       attr_writer :run_after_load_paths # :nodoc:
       delegate :execute_if_updated, :execute, :updated?, to: :updater
@@ -17,9 +17,11 @@ def initialize
         @route_sets = []
         @external_routes = []
         @eager_load = false
+        @loaded = false
       end
 
       def reload!
+        @loaded = true
         clear!
         load_paths
         finalize!
@@ -28,6 +30,14 @@ def reload!
         revert
       end
 
+      def execute_unless_loaded
+        unless @loaded
+          execute
+          ActiveSupport.run_load_hooks(:after_routes_loaded, Rails.application)
+          true
+        end
+      end
+
     private
       def updater
         @updater ||= begin

railties/lib/rails/engine.rb

@@ -349,6 +349,7 @@ module Rails
   #   config.railties_order = [Blog::Engine, :main_app, :all]
   class Engine < Railtie
     autoload :Configuration, "rails/engine/configuration"
+    autoload :LazyRouteSet,  "rails/engine/lazy_route_set"
 
     class << self
       attr_accessor :called_from, :isolated
@@ -385,7 +386,8 @@ def endpoint(endpoint = nil)
       def isolate_namespace(mod)
         engine_name(generate_railtie_name(mod.name))
 
-        routes.default_scope = { module: ActiveSupport::Inflector.underscore(mod.name) }
+        config.default_scope = { module: ActiveSupport::Inflector.underscore(mod.name) }
+
         self.isolated = true
 
         unless mod.respond_to?(:railtie_namespace)
@@ -543,7 +545,7 @@ def env_config
     # Defines the routes for this engine. If a block is given to
     # routes, it is appended to the engine.
     def routes(&block)
-      @routes ||= ActionDispatch::Routing::RouteSet.new_with_config(config)
+      @routes ||= config.route_set_class.new_with_config(config)
       @routes.append(&block) if block_given?
       @routes
     end
@@ -588,6 +590,10 @@ def load_seed
       config.eager_load_paths.freeze
     end
 
+    initializer :make_routes_lazy, before: :set_routes_reloader_hook do |app|
+      config.route_set_class = LazyRouteSet if Rails.env.local?
+    end
+
     initializer :add_routing_paths do |app|
       routing_paths = paths["config/routes.rb"].existent
       external_paths = self.paths["config/routes"].paths

railties/lib/rails/engine/configuration.rb

@@ -6,7 +6,7 @@ module Rails
   class Engine
     class Configuration < ::Rails::Railtie::Configuration
       attr_reader :root
-      attr_accessor :middleware, :javascript_path
+      attr_accessor :middleware, :javascript_path, :route_set_class, :default_scope
       attr_writer :eager_load_paths, :autoload_once_paths, :autoload_paths
 
       # An array of custom autoload paths to be added to the ones defined
@@ -44,6 +44,8 @@ def initialize(root = nil)
         @generators = app_generators.dup
         @middleware = Rails::Configuration::MiddlewareStackProxy.new
         @javascript_path = "javascript"
+        @route_set_class = ActionDispatch::Routing::RouteSet
+        @default_scope = nil
 
         @autoload_paths = []
         @autoload_once_paths = []

railties/lib/rails/engine/lazy_route_set.rb

@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+# :markup: markdown
+
+require "action_dispatch/routing/route_set"
+
+module Rails
+  class Engine
+    class LazyRouteSet < ActionDispatch::Routing::RouteSet # :nodoc:
+      class NamedRouteCollection < ActionDispatch::Routing::RouteSet::NamedRouteCollection
+        def route_defined?(name)
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+      end
+
+      module ProxyUrlHelpers
+        def url_for(options)
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+
+        def full_url_for(options)
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+
+        def route_for(name, *args)
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+
+        def optimize_routes_generation?
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+
+        def polymorphic_url(record_or_hash_or_array, options = {})
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+
+        def polymorphic_path(record_or_hash_or_array, options = {})
+          Rails.application&.reload_routes_unless_loaded
+          super
+        end
+      end
+
+      def initialize(config = DEFAULT_CONFIG)
+        super
+        self.named_routes = NamedRouteCollection.new
+        named_routes.url_helpers_module.prepend(method_missing_module)
+        named_routes.path_helpers_module.prepend(method_missing_module)
+      end
+
+      def generate_extras(options, recall = {})
+        Rails.application&.reload_routes_unless_loaded
+
+        super(options, recall)
+      end
+
+      def generate_url_helpers(supports_path)
+        super.tap { |mod| mod.singleton_class.prepend(ProxyUrlHelpers) }
+      end
+
+      def call(req)
+        Rails.application&.reload_routes_unless_loaded
+        super
+      end
+
+      def draw(&block)
+        Rails.application&.reload_routes_unless_loaded
+        super
+      end
+
+      def routes
+        Rails.application&.reload_routes_unless_loaded
+        super
+      end
+
+      private
+        def method_missing_module
+          @method_missing_module ||= Module.new do
+            private
+              def method_missing(method_name, *args, &block)
+                if Rails.application&.reload_routes_unless_loaded
+                  public_send(method_name, *args, &block)
+                else
+                  super(method_name, *args, &block)
+                end
+              end
+
+              def respond_to_missing?(method_name, *args)
+                if Rails.application&.reload_routes_unless_loaded
+                  respond_to?(method_name, *args)
+                else
+                  super(method_name, *args)
+                end
+              end
+          end
+        end
+    end
+  end
+end