Lazy evaluate middleware arguments [#2028 state:resolved]

Signed-off-by: NJoshua Peek <josh@joshpeek.com>

actionpack/lib/action_controller/middleware_stack.rb

@@ -67,11 +67,17 @@ def inspect
 
       def build(app)
         if block
-          klass.new(app, *args, &block)
+          klass.new(app, *build_args, &block)
         else
-          klass.new(app, *args)
+          klass.new(app, *build_args)
         end
       end
+
+      private
+
+        def build_args
+          Array(args).map { |arg| arg.respond_to?(:call) ? arg.call : arg }
+        end
     end
 
     def initialize(*args, &block)

actionpack/lib/action_controller/middlewares.rb

@@ -5,7 +5,7 @@
 use "ActionController::Failsafe"
 
 use lambda { ActionController::Base.session_store },
-  ActionController::Base.session_options
+    lambda { ActionController::Base.session_options }
 
 use "ActionController::RewindableInput"
 use "ActionController::ParamsParser"

actionpack/test/controller/middleware_stack_test.rb

@@ -80,4 +80,11 @@ def setup
     end
     assert_equal BazMiddleware, @stack.last.klass
   end
+
+  test "lazy evaluates middleware arguments" do
+    assert_difference "@stack.size" do
+      @stack.use BazMiddleware, lambda { :foo }
+    end
+    assert_equal [:foo], @stack.last.send(:build_args)
+  end
 end