Refactor Plugin Loader. Add plugin lib paths early, and add lots of t…

…ests. Closes #9795 [lazyatom]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8115 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

railties/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Refactor Plugin Loader.  Add plugin lib paths early, and add lots of tests.  Closes #9795 [lazyatom]
+
 * Added --skip-timestamps to generators that produce models #10036 [tpope]
 
 * Update Prototype to 1.6.0 and script.aculo.us to 1.8.0.  [sam, madrobby]

railties/lib/initializer.rb

@@ -34,7 +34,7 @@ class Initializer
 
     # The set of loaded plugins.
     attr_reader :loaded_plugins
-
+    
     # Runs the initializer. By default, this will invoke the #process method,
     # which simply executes all of the initialization routines. Alternately,
     # you can specify explicitly which initialization routine you want:
@@ -64,6 +64,7 @@ def initialize(configuration)
     # * #set_load_path
     # * #require_frameworks
     # * #set_autoload_paths
+    # * add_plugin_load_paths
     # * #load_environment
     # * #initialize_encoding
     # * #initialize_database
@@ -83,9 +84,10 @@ def initialize(configuration)
     def process
       check_ruby_version
       set_load_path
-
+      
       require_frameworks
       set_autoload_paths
+      add_plugin_load_paths
       load_environment
 
       initialize_encoding
@@ -161,14 +163,20 @@ def require_frameworks
     def add_support_load_paths
     end
 
+    # Adds all load paths from plugins to the global set of load paths, so that
+    # code from plugins can be required (explicitly or automatically via Dependencies).
+    def add_plugin_load_paths
+      plugin_loader.add_plugin_load_paths
+    end
+
     # Loads all plugins in <tt>config.plugin_paths</tt>.  <tt>plugin_paths</tt>
     # defaults to <tt>vendor/plugins</tt> but may also be set to a list of
     # paths, such as
     #   config.plugin_paths = ["#{RAILS_ROOT}/lib/plugins", "#{RAILS_ROOT}/vendor/plugins"]
     #
-    # Each plugin discovered in <tt>plugin_paths</tt> is initialized:
-    # * add its +lib+ directory, if present, to the beginning of the load path
-    # * evaluate <tt>init.rb</tt> if present
+    # In the default implementation, as each plugin discovered in <tt>plugin_paths</tt> is initialized:
+    # * its +lib+ directory, if present, is added to the load path (immediately after the applications lib directory)
+    # * <tt>init.rb</tt> is evalutated, if present
     #
     # After all plugins are loaded, duplicates are removed from the load path.
     # If an array of plugin names is specified in config.plugins, only those plugins will be loaded
@@ -178,13 +186,11 @@ def add_support_load_paths
     # if config.plugins ends contains :all then the named plugins will be loaded in the given order and all other
     # plugins will be loaded in alphabetical order
     def load_plugins
-      configuration.plugin_locators.each do |locator|
-        locator.new(self).each do |plugin|
-          plugin.load
-        end
-      end
-      ensure_all_registered_plugins_are_loaded!
-      $LOAD_PATH.uniq!
+      plugin_loader.load_plugins
+    end
+
+    def plugin_loader
+      @plugin_loader ||= configuration.plugin_loader.new(self)
     end
 
     # Loads the environment specified by Configuration#environment_path, which
@@ -337,15 +343,6 @@ def load_application_initializers
       end
     end
 
-    private
-      def ensure_all_registered_plugins_are_loaded!
-        unless configuration.plugins.nil?
-          if configuration.plugins.detect {|plugin| plugin != :all && !loaded_plugins.include?( plugin)}
-            missing_plugins = configuration.plugins - (loaded_plugins + [:all])
-            raise LoadError, "Could not locate the following plugins: #{missing_plugins.to_sentence}"
-          end
-        end
-      end
   end
 
   # The Configuration class holds all the parameters for the Initializer and

railties/lib/rails/plugin.rb

@@ -0,0 +1,83 @@
+module Rails
+
+  # The Plugin class should be an object which provides the following methods:
+  #
+  # * +name+       - used during initialisation to order the plugin (based on name and
+  #                  the contents of <tt>config.plugins</tt>)
+  # * +valid?+     - returns true if this plugin can be loaded
+  # * +load_paths+ - each path within the returned array will be added to the $LOAD_PATH
+  # * +load+       - finally 'load' the plugin.
+  #
+  # These methods are expected by the Rails::Plugin::Locator and Rails::Plugin::Loader classes.
+  # The default implementation returns the <tt>lib</tt> directory as its </tt>load_paths</tt>, 
+  # and evaluates <tt>init.rb</tt> when <tt>load</tt> is called.
+  class Plugin
+    include Comparable
+
+    attr_reader :directory, :name
+
+    def initialize(directory)
+      @directory = directory
+      @name = File.basename(@directory) rescue nil
+      @loaded = false
+    end
+
+    def valid?
+      File.directory?(directory) && (has_lib_directory? || has_init_file?)
+    end
+
+    # Returns a list of paths this plugin wishes to make available in $LOAD_PATH
+    def load_paths
+      report_nonexistant_or_empty_plugin! unless valid?
+      has_lib_directory? ? [lib_path] : []
+    end
+
+    # Evaluates a plugin's init.rb file
+    def load(initializer)
+      report_nonexistant_or_empty_plugin! unless valid?
+      evaluate_init_rb(initializer)
+      @loaded = true
+    end
+
+    def loaded?
+      @loaded
+    end
+
+    def <=>(other_plugin)
+      name <=> other_plugin.name
+    end
+
+    private
+
+      def report_nonexistant_or_empty_plugin!
+        raise LoadError, "Can not find the plugin named: #{name}"
+      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 evaluate_init_rb(initializer)
+         if has_init_file?
+           silence_warnings do
+             # Allow plugins to reference the current configuration object
+             config = initializer.configuration
+
+             eval(IO.read(init_path), binding, init_path)
+           end
+         end
+      end               
+  end
+end