Refactor highlight tag to behave like the raw tag (#6821)

Merge pull request 6821

lib/jekyll/tags/highlight.rb

@@ -2,7 +2,7 @@
 
 module Jekyll
   module Tags
-    class HighlightBlock < Liquid::Block
+    class HighlightBlock < Liquid::Raw
       include Liquid::StandardFilters
 
       # The regular expression syntax checker. Start with the language specifier.
@@ -28,10 +28,12 @@ module Jekyll
         end
       end
 
+      LEADING_OR_TRAILING_LINE_TERMINATORS = %r!\A(\n|\r)+|(\n|\r)+\z!.freeze
+
       def render(context)
         prefix = context["highlighter_prefix"] || ""
         suffix = context["highlighter_suffix"] || ""
-        code = super.to_s.gsub(%r!\A(\n|\r)+|(\n|\r)+\z!, "")
+        code   = @body.gsub(LEADING_OR_TRAILING_LINE_TERMINATORS, "")
 
         output =
           case context.registers[:site].highlighter
@@ -101,6 +103,8 @@ module Jekyll
         "<figure class=\"highlight\"><pre><code #{code_attributes}>"\
         "#{code.chomp}</code></pre></figure>"
       end
+
+      def ensure_valid_markup(tag_name, markup, parse_context); end
     end
   end
 end