Allow loading of only specific Rails modules.

lib/combustion.rb

@@ -1,12 +1,15 @@
 require 'rails'
 require 'active_support/dependencies'
-require 'active_record/railtie'
-require 'action_controller/railtie'
-require 'action_view/railtie'
-require 'sprockets/railtie'
 
 module Combustion
-  def self.initialize!
+  Modules = %w( active_record action_controller action_view action_mailer
+    sprockets )
+
+  def self.initialize!(*modules)
+    modules = Modules if modules.empty? || modules == [:all]
+    modules.each { |mod| require "#{mod}/railtie" }
+
+    Combustion::Application.configure_for_combustion
     Combustion::Application.initialize!
 
     silence_stream(STDOUT) do
@@ -18,7 +21,7 @@ def self.initialize!
 
       config.include(Combustion::Application.routes.url_helpers)
       config.include(Combustion::Application.routes.mounted_helpers)
-    end if defined?(RSpec)
+    end if defined?(RSpec) && RSpec.respond_to?(:configure)
   end
 end
 

lib/combustion/application.rb

@@ -12,15 +12,23 @@ class Combustion::Application < Rails::Application
   # ActiveSupport Settings
   config.active_support.deprecation = :stderr
 
-  # Action Controller and Action Dispatch
-  config.action_dispatch.show_exceptions            = false
-  config.action_controller.perform_caching          = false
-  config.action_controller.allow_forgery_protection = false
+  # Some settings we're not sure if we want, so let's not load them by default.
+  # Instead, wait for this method to be invoked (to get around load-order
+  # complications).
+  def self.configure_for_combustion
+    if defined?(ActionController) && defined?(ActionController::Engine)
+      config.action_dispatch.show_exceptions            = false
+      config.action_controller.perform_caching          = false
+      config.action_controller.allow_forgery_protection = false
+    end
 
-  # Action Mailer Settings
-  # config.action_mailer.delivery_method      = :test
-  # config.action_mailer.default_url_options  = {:host => 'www.example.com'}
+    if defined?(ActionMailer) && defined?(ActionMailer::Engine)
+      config.action_mailer.delivery_method     = :test
+      config.action_mailer.default_url_options = {:host => 'www.example.com'}
+    end
 
-  # Asset Settings
-  config.assets.enabled = true
+    if defined?(Sprockets)
+      config.assets.enabled = true
+    end
+  end
 end