Fix ArgumentError when block given with keyword arguments

lib/rabl/engine.rb

@@ -356,8 +356,8 @@ def respond_to?(name, include_private = false)
       end
 
       # Supports calling helpers defined for the template context_scope using method_missing hook
-      def method_missing(name, *args, &block)
-        context_scope.respond_to?(name, true) ? context_scope.__send__(name, *args, &block) : super
+      def method_missing(name, *args, **kwargs, &block)
+        context_scope.respond_to?(name, true) ? context_scope.__send__(name, *args, **kwargs, &block) : super
       end
 
       def copy_instance_variables_from(object, exclude = []) #:nodoc:

test/engine_test.rb

@@ -27,6 +27,15 @@
     denies("that it raises exception when given frozen locals").raises(RuntimeError) do
       Rabl::Engine.new("").apply(Object.new, {}.freeze)
     end
+
+    asserts "that it can call method in block with positional and keyword arguments" do
+      template = RablTemplate.new("code") { 'node(:foo) { func("bar", kw: "baz") }' }
+      obj = Object.new
+      def obj.func(arg, kw:)
+        "#{arg}-#{kw}"
+      end
+      template.render(obj)
+    end.equals "{\"foo\":\"bar-baz\"}"
   end
 
   context "#request_format" do