Avoid (@_var ||= nil) pattern by using initialize methods and ensuring everyone calls super as expected.

actionpack/lib/abstract_controller/layouts.rb

@@ -345,11 +345,9 @@ module AbstractController
     # * <tt>template</tt> - The template object for the default layout (or nil)
     def _default_layout(require_layout = false)
       begin
-        @_layout ||= nil
         layout_name = _layout if action_has_layout?
       rescue NameError => e
-        raise NoMethodError,
-          "You specified #{@_layout.inspect} as the layout, but no such method was found"
+        raise e.class, "Coult not render layout: #{e.message}"
       end
 
       if require_layout && action_has_layout? && !layout_name

actionpack/lib/abstract_controller/rendering.rb

@@ -66,7 +66,7 @@ module AbstractController
     attr_writer :view_context_class
 
     def view_context_class
-      (@view_context_class ||= nil) || self.class.view_context_class
+      @view_context_class || self.class.view_context_class
     end
 
     def initialize(*)

actionpack/lib/abstract_controller/url_for.rb

@@ -1,7 +1,6 @@
 module AbstractController
   module UrlFor
     extend ActiveSupport::Concern
-
     include ActionDispatch::Routing::UrlFor
 
     def _routes

actionpack/lib/action_dispatch/middleware/stack.rb

@@ -41,7 +41,11 @@ module ActionDispatch
       end
     end
 
+    # Use this instead of super to work around a warning.
+    alias :array_initialize :initialize
+
     def initialize(*args)
+      array_initialize(*args)
       yield(self) if block_given?
     end
 

actionpack/lib/action_dispatch/middleware/static.rb

@@ -4,10 +4,9 @@ module ActionDispatch
   class FileHandler
     def initialize(at, root)
       @at, @root = at.chomp('/'), root.chomp('/')
-      @compiled_at = Regexp.compile(/^#{Regexp.escape(at)}/) unless @at.blank?
+      @compiled_at = (Regexp.compile(/^#{Regexp.escape(at)}/) unless @at.blank?)
       @compiled_root = Regexp.compile(/^#{Regexp.escape(root)}/)
       @file_server = ::Rack::File.new(root)
-      @compiled_at ||= nil
     end
 
     def match?(path)

actionpack/lib/action_dispatch/routing/url_for.rb

@@ -98,6 +98,11 @@ module ActionDispatch
         end
       end
 
+      def initialize(*)
+        @_routes = nil
+        super
+      end
+
       def url_options
         default_url_options
       end
@@ -136,7 +141,6 @@ module ActionDispatch
 
       protected
         def _with_routes(routes)
-          @_routes ||= nil
           old_routes, @_routes = @_routes, routes
           yield
         ensure

actionpack/lib/action_dispatch/testing/integration.rb

@@ -171,6 +171,7 @@ module ActionDispatch
 
       # Create and initialize a new Session instance.
       def initialize(app)
+        super
         @app = app
 
         # If the app is a Rails app, make url_helpers available on the session

actionpack/lib/action_view/helpers/form_helper.rb

@@ -850,7 +850,7 @@ module ActionView
       extend ActiveSupport::Concern
       include Helpers::CaptureHelper, Context, Helpers::TagHelper, Helpers::FormTagHelper
 
-      attr_reader :method_name, :object_name
+      attr_reader :object, :method_name, :object_name
 
       DEFAULT_FIELD_OPTIONS     = { "size" => 30 }
       DEFAULT_RADIO_OPTIONS     = { }
@@ -859,14 +859,9 @@ module ActionView
       def initialize(object_name, method_name, template_object, object = nil)
         @object_name, @method_name = object_name.to_s.dup, method_name.to_s.dup
         @template_object = template_object
-        @object = object
-        if @object_name.sub!(/\[\]$/,"") || @object_name.sub!(/\[\]\]$/,"]")
-          if (object ||= @template_object.instance_variable_get("@#{Regexp.last_match.pre_match}")) && object.respond_to?(:to_param)
-            @auto_index = object.to_param
-          else
-            raise ArgumentError, "object[] naming but object param and @object var don't exist or don't respond to to_param: #{object.inspect}"
-          end
-        end
+        @object_name.sub!(/\[\]$/,"") || @object_name.sub!(/\[\]\]$/,"]")
+        @object = retrieve_object(object)
+        @auto_index = retrieve_autoindex(Regexp.last_match.pre_match) if Regexp.last_match
       end
 
       def to_label_tag(text = nil, options = {}, &block)
@@ -990,18 +985,26 @@ module ActionView
         content_tag(tag_name, value(object), options)
       end
 
-      def object
-        if @object
-          @object
+      def retrieve_object(object)
+        if object
+          object
         elsif @template_object.instance_variable_defined?("@#{@object_name}")
           @template_object.instance_variable_get("@#{@object_name}")
         end
       rescue NameError
-        # As @object_name may contain the nested syntax (item[subobject]) we
-        # need to fallback to nil.
+        # As @object_name may contain the nested syntax (item[subobject]) we need to fallback to nil.
         nil
       end
 
+      def retrieve_autoindex(pre_match)
+        object = self.object || @template_object.instance_variable_get("@#{pre_match}")
+        if object && object.respond_to?(:to_param)
+          object.to_param
+        else
+          raise ArgumentError, "object[] naming but object param and @object var don't exist or don't respond to to_param: #{object.inspect}"
+        end
+      end
+
       def value(object)
         self.class.value(object, @method_name)
       end

actionpack/lib/action_view/test_case.rb

@@ -20,12 +20,12 @@ module ActionView
       end
 
       def initialize
+        super
         self.class.controller_path = ""
         @request = ActionController::TestRequest.new
         @response = ActionController::TestResponse.new
 
         @request.env.delete('PATH_INFO')
-
         @params = {}
       end
     end
@@ -156,15 +156,15 @@ module ActionView
       # The instance of ActionView::Base that is used by +render+.
       def view
         @view ||= begin
-                     view = ActionView::Base.new(ActionController::Base.view_paths, {}, @controller)
-                     view.singleton_class.send :include, _helpers
-                     view.singleton_class.send :include, @controller._routes.url_helpers
-                     view.singleton_class.send :delegate, :alert, :notice, :to => "request.flash"
-                     view.extend(Locals)
-                     view.locals = self.locals
-                     view.output_buffer = self.output_buffer
-                     view
-                   end
+          view = ActionView::Base.new(ActionController::Base.view_paths, {}, @controller)
+          view.singleton_class.send :include, _helpers
+          view.singleton_class.send :include, @controller._routes.url_helpers
+          view.singleton_class.send :delegate, :alert, :notice, :to => "request.flash"
+          view.extend(Locals)
+          view.locals = self.locals
+          view.output_buffer = self.output_buffer
+          view
+        end
       end
 
       alias_method :_view, :view
@@ -201,7 +201,7 @@ module ActionView
 
       def method_missing(selector, *args)
         if @controller.respond_to?(:_routes) &&
-        @controller._routes.named_routes.helpers.include?(selector)
+          @controller._routes.named_routes.helpers.include?(selector)
           @controller.__send__(selector, *args)
         else
           super

actionpack/test/abstract/layouts_test.rb

@@ -225,7 +225,7 @@ module AbstractControllerTests
       end
 
       test "when the layout is specified as a symbol and the method doesn't exist, raise an exception" do
-        assert_raises(NoMethodError) { WithSymbolAndNoMethod.new.process(:index) }
+        assert_raises(NameError) { WithSymbolAndNoMethod.new.process(:index) }
       end
 
       test "when the layout is specified as a symbol and the method returns something besides a string/false/nil, raise an exception" do