Fix resource counting bug with respond_to?(:length)

test/liquid/template_test.rb

@@ -14,6 +14,14 @@ class TemplateContextDrop < Liquid::Drop
   end
 end
 
+class SomethingWithLength
+  def length
+    nil
+  end
+
+  liquid_methods :length
+end
+
 class TemplateTest < Test::Unit::TestCase
   include Liquid
 
@@ -86,6 +94,12 @@ class TemplateTest < Test::Unit::TestCase
     @global = nil
   end
 
+  def test_resource_limits_works_with_custom_length_method
+    t = Template.parse("{% assign foo = bar %}")
+    t.resource_limits = { :render_length_limit => 42 }
+    assert_equal "", t.render("bar" => SomethingWithLength.new)
+  end
+
   def test_resource_limits_render_length
     t = Template.parse("0123456789")
     t.resource_limits = { :render_length_limit => 5 }