1 files changed, 123 insertions, 0 deletions
diff --git a/railties/lib/rails/plugin/loader.rb b/railties/lib/rails/plugin/loader.rb
new file mode 100644
index 0000000000..d5ad3aa8e3
--- /dev/null
+++ b/railties/lib/rails/plugin/loader.rb
@@ -0,0 +1,123 @@
+module Rails
+  module Plugin
+    class Loader
+      include Comparable
+      attr_reader :initializer, :directory, :name
+  
+      class << self
+        def load(*args)
+          new(*args).load
+        end
+      end
+  
+      def initialize(initializer, directory)
+        @initializer = initializer
+        @directory   = directory
+        @name        = File.basename(directory)
+      end
+  
+      def load
+        return false if loaded?
+        report_nonexistant_or_empty_plugin!
+        add_to_load_path!
+        register_plugin_as_loaded
+        evaluate
+        true
+      end
+  
+      def loaded?
+        initializer.loaded_plugins.include?(name)
+      end
+  
+      def plugin_path?
+        File.directory?(directory) && (has_lib_directory? || has_init_file?)
+      end
+      
+      def enabled?
+        !explicit_plugin_loading_order? || registered?
+      end
+        
+      def registered?
+        explicit_plugin_loading_order? && registered_plugins.include?(name)
+      end
+      
+      def plugin_does_not_exist!(plugin_name = name)
+        raise LoadError, "Can not find the plugin named: #{plugin_name}"
+      end
+      
+      private
+        # The plugins that have been explicitly listed with config.plugins. If this list is nil
+        # then it means the client does not care which plugins or in what order they are loaded, 
+        # so we load all in alphabetical order. If it is an empty array, we load no plugins, if it is
+        # non empty, we load the named plugins in the order specified.
+        def registered_plugins
+          config.plugins
+        end
+        
+        def explicit_plugin_loading_order?
+          !registered_plugins.nil?
+        end
+        
+        def report_nonexistant_or_empty_plugin!
+          plugin_does_not_exist! unless plugin_path?
+        end
+        
+        def lib_path
+          File.join(directory, 'lib')
+        end
+  
+        def init_path
+          File.join(directory, 'init.rb')
+        end
+  
+        def has_lib_directory?
+          File.directory?(lib_path)
+        end
+  
+        def has_init_file?
+          File.file?(init_path)
+        end
+  
+        def add_to_load_path!
+          # Add lib to load path *after* the application lib, to allow
+          # application libraries to override plugin libraries.
+          if has_lib_directory?
+            application_lib_index = $LOAD_PATH.index(application_library_path) || 0
+            $LOAD_PATH.insert(application_lib_index + 1, lib_path)
+            Dependencies.load_paths      << lib_path
+            Dependencies.load_once_paths << lib_path
+          end
+        end
+      
+        def application_library_path
+          File.join(RAILS_ROOT, 'lib')
+        end
+  
+        # Allow plugins to reference the current configuration object
+        def config
+          initializer.configuration
+        end
+  
+        def register_plugin_as_loaded
+          initializer.loaded_plugins << name
+        end
+  
+        # Evaluate in init.rb
+        def evaluate
+          silence_warnings { eval(IO.read(init_path), binding, init_path)} if has_init_file?
+        end
+      
+        def <=>(other_plugin_loader)
+          if explicit_plugin_loading_order?
+            if non_existent_plugin = [self, other_plugin_loader].detect {|plugin| !registered_plugins.include?(plugin.name)}
+              plugin_does_not_exist!(non_existent_plugin.name)
+            end
+            
+            registered_plugins.index(name) <=> registered_plugins.index(other_plugin_loader.name)
+          else
+            name <=> other_plugin_loader.name
+          end
+        end
+    end
+  end
+end