Pop the for_stack register in an ensure

lib/liquid/tags/for.rb

@@ -132,8 +132,9 @@ module Liquid
         end
       end
 
-      for_stack.pop
       result
+    ensure
+      for_stack.pop
     end
 
     protected

test/integration/error_handling_test.rb

@@ -1,24 +1,5 @@
 require 'test_helper'
 
-class ErrorDrop < Liquid::Drop
-  def standard_error
-    raise Liquid::StandardError, 'standard error'
-  end
-
-  def argument_error
-    raise Liquid::ArgumentError, 'argument error'
-  end
-
-  def syntax_error
-    raise Liquid::SyntaxError, 'syntax error'
-  end
-
-  def exception
-    raise Exception, 'exception'
-  end
-
-end
-
 class ErrorHandlingTest < Minitest::Test
   include Liquid
 

test/integration/tags/for_tag_test.rb

@@ -388,4 +388,14 @@ HERE
     assert_template_result(expected, template, loader_assigns)
     assert_template_result(expected, template, array_assigns)
   end
+
+  def test_for_cleans_up_registers
+    context = Context.new(ErrorDrop.new)
+
+    assert_raises(StandardError) do
+      Liquid::Template.parse('{% for i in (1..2) %}{{ standard_error }}{% endfor %}').render!(context)
+    end
+
+    assert context.registers[:for_stack].empty?
+  end
 end

test/test_helper.rb

@@ -88,3 +88,22 @@ class ThingWithToLiquid
     'foobar'
   end
 end
+
+class ErrorDrop < Liquid::Drop
+  def standard_error
+    raise Liquid::StandardError, 'standard error'
+  end
+
+  def argument_error
+    raise Liquid::ArgumentError, 'argument error'
+  end
+
+  def syntax_error
+    raise Liquid::SyntaxError, 'syntax error'
+  end
+
+  def exception
+    raise Exception, 'exception'
+  end
+end
+