Lazy evaluate middleware arguments [#2028 state:resolved]

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

3 files changed, 16 insertions, 3 deletions

diff --git a/actionpack/lib/action_controller/middleware_stack.rb b/actionpack/lib/action_controller/middleware_stack.rb
index ee0ae48ac0..b739a6d72d 100644
--- a/actionpack/lib/action_controller/middleware_stack.rb
+++ b/actionpack/lib/action_controller/middleware_stack.rb
@@ -67,11 +67,17 @@ module ActionController
 
       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)
diff --git a/actionpack/lib/action_controller/middlewares.rb b/actionpack/lib/action_controller/middlewares.rb
index fd70eca1b1..371cf6d8f7 100644
--- a/actionpack/lib/action_controller/middlewares.rb
+++ b/actionpack/lib/action_controller/middlewares.rb
@@ -5,7 +5,7 @@ use "Rack::Lock", :if => lambda {
 use "ActionController::Failsafe"
 
 use lambda { ActionController::Base.session_store },
-  ActionController::Base.session_options
+    lambda { ActionController::Base.session_options }
 
 use "ActionController::RewindableInput"
 use "ActionController::ParamsParser"
diff --git a/actionpack/test/controller/middleware_stack_test.rb b/actionpack/test/controller/middleware_stack_test.rb
index 612a710fa7..918231013a 100644
--- a/actionpack/test/controller/middleware_stack_test.rb
+++ b/actionpack/test/controller/middleware_stack_test.rb
@@ -80,4 +80,11 @@ class MiddlewareStackTest < ActiveSupport::TestCase
     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