Make sure after_routes_loaded hook runs on boot

This hook was only running when routes were reloaded, but not on boot.

The goal was to run any time routes are loaded. This commit fixes it
and adds a test.

Fixes rails#50720.

Author: rafaelfranca

railties/lib/rails/application/finisher.rb

@@ -161,6 +161,7 @@ def self.complete(_state)
         reloader.eager_load = app.config.eager_load
         reloader.execute
         reloaders << reloader
+
         app.reloader.to_run do
           # We configure #execute rather than #execute_if_updated because if
           # autoloaded constants are cleared we need to reload routes also in
@@ -175,6 +176,8 @@ def self.complete(_state)
           reloader.execute
           ActiveSupport.run_load_hooks(:after_routes_loaded, self)
         end
+
+        ActiveSupport.run_load_hooks(:after_routes_loaded, self)
       end
 
       # Set clearing dependencies after the finisher hook to ensure paths

railties/test/application/loading_test.rb

@@ -324,12 +324,12 @@ class User
     require "#{rails_root}/config/environment"
 
     get "/c"
-    assert_equal "3", last_response.body
+    assert_equal "7", last_response.body
 
     app_file "db/schema.rb", ""
 
     get "/c"
-    assert_equal "19", last_response.body
+    assert_equal "43", last_response.body
   end
 
   test "routes are only loaded once on boot" do
@@ -356,6 +356,36 @@ class User
     assert_equal "1", last_response.body
   end
 
+  test "after_routes_loaded runs once on boot" do
+    add_to_config <<-RUBY
+      config.enable_reloading = true
+    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
+
+    app_file "config/initializers/after_routes_loaded.rb", <<-RUBY
+      Rails.configuration.after_routes_loaded do
+        $counter *= 3
+      end
+    RUBY
+
+    boot_app "development"
+
+    require "rack/test"
+    extend Rack::Test::Methods
+
+    require "#{rails_root}/config/environment"
+
+    get "/c"
+    assert_equal "3", last_response.body
+  end
+
   test "columns migrations also trigger reloading" do
     add_to_config <<-RUBY
       config.enable_reloading = true