Fix a bug in ActionDispatch::Static where Rails cannot find assets if started in another directory which is not the RAILS_ROOT.

actionpack/lib/action_controller/caching/pages.rb

@@ -38,22 +38,22 @@ module ActionController #:nodoc:
       extend ActiveSupport::Concern
 
       included do
-        @@page_cache_directory = defined?(Rails.public_path) ? Rails.public_path : ""
         ##
         # :singleton-method:
         # The cache directory should be the document root for the web server and is set using <tt>Base.page_cache_directory = "/document/root"</tt>.
         # For Rails, this directory has already been set to Rails.public_path (which is usually set to <tt>RAILS_ROOT + "/public"</tt>). Changing
         # this setting can be useful to avoid naming conflicts with files in <tt>public/</tt>, but doing so will likely require configuring your
         # web server to look in the new location for cached files.
+        @@page_cache_directory = ''
         cattr_accessor :page_cache_directory
 
-        @@page_cache_extension = '.html'
         ##
         # :singleton-method:
         # Most Rails requests do not have an extension, such as <tt>/weblog/new</tt>. In these cases, the page caching mechanism will add one in
         # order to make it easy for the cached files to be picked up properly by the web server. By default, this cache extension is <tt>.html</tt>.
         # If you want something else, like <tt>.php</tt> or <tt>.shtml</tt>, just set Base.page_cache_extension. In cases where a request already has an
         # extension, such as <tt>.xml</tt> or <tt>.rss</tt>, page caching will not add an extension. This allows it to work well with RESTful apps.
+        @@page_cache_extension = '.html'
         cattr_accessor :page_cache_extension
       end
 

actionpack/lib/action_controller/metal/compatibility.rb

@@ -32,8 +32,6 @@ module ActionController
       def rescue_action(env)
         raise env["action_dispatch.rescue.exception"]
       end
-
-      self.page_cache_directory = defined?(Rails.public_path) ? Rails.public_path : ""
     end
 
     # For old tests

actionpack/lib/action_controller/railtie.rb

@@ -44,6 +44,12 @@ module ActionController
       ActiveSupport.on_load(:action_controller) { self.logger ||= Rails.logger }
     end
 
+    initializer "action_controller.page_cache_directory" do
+      ActiveSupport.on_load(:action_controller) do
+        self.page_cache_directory = Rails.public_path
+      end
+    end
+
     initializer "action_controller.set_configs" do |app|
       paths = app.config.paths
       ac = app.config.action_controller

railties/lib/rails.rb

@@ -92,11 +92,12 @@ module Rails
     end
 
     def public_path
-      @@public_path ||= self.root ? File.join(self.root, "public") : "public"
+      application && application.paths.public.to_a.first
     end
 
     def public_path=(path)
-      @@public_path = path
+      ActiveSupport::Deprecation.warn "Setting Rails.public_path= is deprecated. " <<
+        "Please set paths.public = in config/application.rb instead.", caller
     end
   end
 end

railties/lib/rails/application/configuration.rb

@@ -137,7 +137,7 @@ module Rails
 
       def default_middleware_stack
         ActionDispatch::MiddlewareStack.new.tap do |middleware|
-          middleware.use('::ActionDispatch::Static', lambda { Rails.public_path }, :if => lambda { serve_static_assets })
+          middleware.use('::ActionDispatch::Static', lambda { paths.public.to_a.first }, :if => lambda { serve_static_assets })
           middleware.use('::Rack::Lock', :if => lambda { !allow_concurrency })
           middleware.use('::Rack::Runtime')
           middleware.use('::Rails::Rack::Logger')

railties/test/application/configuration_test.rb

@@ -184,6 +184,15 @@ module ApplicationTests
       end
     end
 
+    test "config.paths.public sets Rails.public_path" do
+      add_to_config <<-RUBY
+        config.paths.public = "somewhere"
+      RUBY
+
+      require "#{app_path}/config/application"
+      assert_equal File.join(app_path, "somewhere"), Rails.public_path
+    end
+
     def make_basic_app
       require "rails"
       require "action_controller/railtie"