Merge pull request #1331 from Shopify/pz-freeze-block

Freeze block body after parsing completes

lib/liquid/block.rb

@@ -13,6 +13,7 @@ module Liquid
       @body = new_body
       while parse_body(@body, tokens)
       end
+      @body.freeze
     end
 
     # For backwards compatibility

lib/liquid/block_body.rb

@@ -19,6 +19,8 @@ module Liquid
     end
 
     def parse(tokenizer, parse_context, &block)
+      raise FrozenError, "can't modify frozen Liquid::BlockBody" if frozen?
+
       parse_context.line_number = tokenizer.line_number
 
       if tokenizer.for_liquid_tag
@@ -28,6 +30,11 @@ module Liquid
       end
     end
 
+    def freeze
+      @nodelist.freeze
+      super
+    end
+
     private def parse_for_liquid_tag(tokenizer, parse_context)
       while (token = tokenizer.shift)
         unless token.empty? || token =~ WhitespaceOrNothing
@@ -192,6 +199,8 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
+      freeze unless frozen?
+
       context.resource_limits.increment_render_score(@nodelist.length)
 
       idx = 0

lib/liquid/document.rb

@@ -22,6 +22,7 @@ module Liquid
     def parse(tokenizer, parse_context)
       while parse_body(tokenizer)
       end
+      @body.freeze
     rescue SyntaxError => e
       e.line_number ||= parse_context.line_number
       raise

lib/liquid/tags/case.rb

@@ -21,8 +21,9 @@ module Liquid
     def parse(tokens)
       body = new_body
       body = @blocks.last.attachment while parse_body(body, tokens)
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      @blocks.each do |condition|
+        condition.attachment.remove_blank_strings if blank?
+        condition.attachment.freeze
       end
     end
 

lib/liquid/tags/for.rb

@@ -66,6 +66,8 @@ module Liquid
         @for_block.remove_blank_strings
         @else_block&.remove_blank_strings
       end
+      @for_block.freeze
+      @else_block&.freeze
     end
 
     def nodelist

lib/liquid/tags/if.rb

@@ -31,8 +31,9 @@ module Liquid
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
-      if blank?
-        @blocks.each { |condition| condition.attachment.remove_blank_strings }
+      @blocks.each do |block|
+        block.attachment.remove_blank_strings if blank?
+        block.attachment.freeze
       end
     end