Accept a Pathname in Application#config_for

That would make possible to use it with action cable configuration.

Author: rafaelfranca

railties/lib/rails/application.rb

@@ -219,7 +219,11 @@ def message_verifier(verifier_name)
     #       config.middleware.use ExceptionNotifier, config_for(:exception_notification)
     #     end
     def config_for(name, env: Rails.env)
-      yaml = Pathname.new("#{paths["config"].existent.first}/#{name}.yml")
+      if name.is_a?(Pathname)
+        yaml = name
+      else
+        yaml = Pathname.new("#{paths["config"].existent.first}/#{name}.yml")
+      end
 
       if yaml.exist?
         require "erb"

railties/test/application/configuration_test.rb

@@ -1306,6 +1306,21 @@ def index
       assert_equal 'custom key', Rails.application.config.my_custom_config['key']
     end
 
+    test "config_for use the Pathname object if it is provided" do
+      app_file 'config/custom.yml', <<-RUBY
+      development:
+        key: 'custom key'
+      RUBY
+
+      add_to_config <<-RUBY
+        config.my_custom_config = config_for(Pathname.new(Rails.root.join("config/custom.yml")))
+      RUBY
+
+      app 'development'
+
+      assert_equal 'custom key', Rails.application.config.my_custom_config['key']
+    end
+
     test "config_for raises an exception if the file does not exist" do
       add_to_config <<-RUBY
         config.my_custom_config = config_for('custom')