Patch for #1458

[3.1.0.rc1] App plugins initialized before engines and plugins inside
engines

It seems that plugins inside a Rails 3.1 application proper (i.e. in
/vendor/plugins) are initialized before engines and plugins inside
engines.

After some debugging, I found the culprit in
Rails::Application::Railties#all:

  def all(&block)
    @ALL ||= railties + engines + super
    @all.each(&block) if block
    @ALL
  end

The call to super here implicitly passes the &block argument, which
has the unfortunate side-effect of adding the plugin initializers
first (in front of other railties and engines) in the case of
Rails::Engine#initializers:

  def initializers
    initializers = []
    railties.all { |r| initializers += r.initializers }
    initializers += super
    initializers
  end

One solution that works here is to change how super is called, e.g.
this works:

  def all(&block)
    @railties_plus_engines ||= railties + engines
    @railties_plus_engines.each(&block) if block
    @railties_plus_engines + super
  end

(Here I'm deliberately not memoizing the result so that super is
always called, and that the block is run against the plugins after it
has been run against the railties and engines first.)

railties/lib/rails/application/railties.rb

@@ -4,9 +4,9 @@ module Rails
   class Application < Engine
     class Railties < Rails::Engine::Railties
       def all(&block)
-        @all ||= railties + engines + super
-        @all.each(&block) if block
-        @all
+        @railties_plus_engines ||= railties + engines
+        @railties_plus_engines.each(&block) if block
+        @railties_plus_engines + super
       end
     end
   end