Merge pull request #298 from Shopify/respond_to_resource_counting_bug

Fix resource counting bug with respond_to?(:length)

History.md

@@ -3,6 +3,7 @@
 ## 3.0.0 / not yet released / branch "master"
 
 * ...
+* Fix resource counting bug with respond_to?(:length), see #263 [Florian Weingarten, fw42]
 * Allow specifying custom patterns for template filenames, see #284 [Andrei Gladkyi, agladkyi]
 * Allow drops to optimize loading a slice of elements, see #282 [Tom Burns, boourns]
 * Support for passing variables to snippets in subdirs, see #271 [Joost Hietbrink, joost]

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
 

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 }