From 796e7129e64d36cbca1c8b11dc48ba5587913217 Mon Sep 17 00:00:00 2001
From: Louis Cloutier <louis.cloutier@shopify.com>
Date: Thu, 3 Dec 2020 11:50:18 -0500
Subject: [PATCH] Only execute route reloads once on boot for development
 environment

Signed-off-by: Louis Cloutier <louis.cloutier@shopify.com>
---
 railties/CHANGELOG.md                         |  4 +++
 railties/lib/rails/application/finisher.rb    | 32 +++++++++----------
 .../lib/rails/application/routes_reloader.rb  | 15 +++++++--
 railties/test/application/loading_test.rb     | 28 ++++++++++++++--
 4 files changed, 59 insertions(+), 20 deletions(-)

diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 06d69fd023..5cfc67c653 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Only execute route reloads once on boot for development environment
+
+    *Louis Cloutier*
+
 *   Removed manifest.js and application.css in app/assets
     folder when --skip-sprockets option passed as flag to rails.
 
diff --git a/railties/lib/rails/application/finisher.rb b/railties/lib/rails/application/finisher.rb
index f996db21a3..ae75ac6c0d 100644
--- a/railties/lib/rails/application/finisher.rb
+++ b/railties/lib/rails/application/finisher.rb
@@ -173,6 +173,22 @@ module Rails
         end
       end
 
+      initializer :add_internal_routes do |app|
+        if Rails.env.development?
+          app.routes.prepend do
+            get "/rails/info/properties" => "rails/info#properties", internal: true
+            get "/rails/info/routes"     => "rails/info#routes",     internal: true
+            get "/rails/info"            => "rails/info#index",      internal: true
+          end
+
+          routes_reloader.after_load_paths = -> do
+            app.routes.append do
+              get "/" => "rails/welcome#index", internal: true
+            end
+          end
+        end
+      end
+
       # Set routes reload after the finisher hook to ensure routes added in
       # the hook are taken into account.
       initializer :set_routes_reloader_hook do |app|
@@ -195,22 +211,6 @@ module Rails
         end
       end
 
-      initializer :add_builtin_route do |app|
-        if Rails.env.development?
-          app.routes.prepend do
-            get "/rails/info/properties" => "rails/info#properties", internal: true
-            get "/rails/info/routes"     => "rails/info#routes", internal: true
-            get "/rails/info"            => "rails/info#index", internal: true
-          end
-
-          app.routes.append do
-            get "/"                      => "rails/welcome#index", internal: true
-          end
-
-          routes_reloader.execute
-        end
-      end
-
       # Set clearing dependencies after the finisher hook to ensure paths
       # added in the hook are taken into account.
       initializer :set_clear_dependencies_hook, group: :all do |app|
diff --git a/railties/lib/rails/application/routes_reloader.rb b/railties/lib/rails/application/routes_reloader.rb
index 3ba31f16c2..8db429f785 100644
--- a/railties/lib/rails/application/routes_reloader.rb
+++ b/railties/lib/rails/application/routes_reloader.rb
@@ -5,10 +5,15 @@ require "active_support/core_ext/module/delegation"
 module Rails
   class Application
     class RoutesReloader
+      include ActiveSupport::Callbacks
+
       attr_reader :route_sets, :paths, :external_routes
-      attr_accessor :eager_load
+      attr_accessor :eager_load, :after_load_paths
       delegate :execute_if_updated, :execute, :updated?, to: :updater
 
+      define_callbacks :load_paths
+      set_callback :load_paths, :after, :run_after_load_paths
+
       def initialize
         @paths      = []
         @route_sets = []
@@ -44,7 +49,13 @@ module Rails
       end
 
       def load_paths
-        paths.each { |path| load(path) }
+        run_callbacks :load_paths do
+          paths.each { |path| load(path) }
+        end
+      end
+
+      def run_after_load_paths
+        after_load_paths.call if after_load_paths.respond_to?(:call)
       end
 
       def finalize!
diff --git a/railties/test/application/loading_test.rb b/railties/test/application/loading_test.rb
index 2d8961eb7f..bff17eb0db 100644
--- a/railties/test/application/loading_test.rb
+++ b/railties/test/application/loading_test.rb
@@ -283,12 +283,36 @@ class LoadingTest < ActiveSupport::TestCase
     require "#{rails_root}/config/environment"
 
     get "/c"
-    assert_equal "5", last_response.body
+    assert_equal "3", last_response.body
 
     app_file "db/schema.rb", ""
 
     get "/c"
-    assert_equal "11", last_response.body
+    assert_equal "7", last_response.body
+  end
+
+  test "routes are only loaded once on boot" do
+    add_to_config <<-RUBY
+      config.cache_classes = false
+    RUBY
+
+    app_file "config/routes.rb", <<-RUBY
+      $counter ||= 0
+      $counter += 1
+      Rails.application.routes.draw do
+        get '/c', to: lambda { |env| [200, {"Content-Type" => "text/plain"}, [$counter.to_s]] }
+      end
+    RUBY
+
+    boot_app "development"
+
+    require "rack/test"
+    extend Rack::Test::Methods
+
+    require "#{rails_root}/config/environment"
+
+    get "/c"
+    assert_equal "1", last_response.body
   end
 
   test "columns migrations also trigger reloading" do