Fix resource counting bug with respond_to?(:length)

lib/liquid/block.rb

@@ -135,7 +135,7 @@ module Liquid
           end
 
           token_output = (token.respond_to?(:render) ? token.render(context) : token)
-          context.resource_limits[:render_length_current] += (token_output.respond_to?(:length) ? token_output.length : 1)
+          context.increment_used_resources(:render_length_current, token_output)
           if context.resource_limits_reached?
             context.resource_limits[:reached] = true
             raise MemoryError.new("Memory limits exceeded")

lib/liquid/context.rb

@@ -28,6 +28,14 @@ module Liquid
       @filters = []
     end
 
+    def increment_used_resources(key, obj)
+      @resource_limits[key] += if obj.class.ancestors & [ String, Array, Hash ] != []
+        obj.length
+      else
+        1
+      end
+    end
+
     def resource_limits_reached?
       (@resource_limits[:render_length_limit] && @resource_limits[:render_length_current] > @resource_limits[:render_length_limit]) ||
       (@resource_limits[:render_score_limit]  && @resource_limits[:render_score_current]  > @resource_limits[:render_score_limit] ) ||

lib/liquid/tags/assign.rb

@@ -25,7 +25,7 @@ module Liquid
     def render(context)
       val = @from.render(context)
       context.scopes.last[@to] = val
-      context.resource_limits[:assign_score_current] += (val.respond_to?(:length) ? val.length : 1)
+      context.increment_used_resources(:assign_score_current, val)
       ''
     end
 

lib/liquid/tags/capture.rb

@@ -27,7 +27,7 @@ module Liquid
     def render(context)
       output = super
       context.scopes.last[@to] = output
-      context.resource_limits[:assign_score_current] += (output.respond_to?(:length) ? output.length : 1)
+      context.increment_used_resources(:assign_score_current, output)
       ''
     end