Add an option to use Rouge's Escape lexer

See rouge-ruby/rouge#1152 See also https://github.com/ole/middleman-syntax/tree/escape-support
honeybadger-io · Feb 1, 2023 · 6d983bc · 6d983bc
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diff --git a/lib/middleman-syntax/extension.rb b/lib/middleman-syntax/extension.rb
@@ -8,6 +8,7 @@ module Middleman
   module Syntax
     class SyntaxExtension < Extension
       option :css_class, 'highlight', 'Class name applied to the syntax-highlighted output.'
+      option :escape, false, 'Allow escaping in code blocks using "<! … !>". WARNING: Can be a security risk if you don’t control the input. See https://github.com/rouge-ruby/rouge/pull/1152 for details.'
       option :line_numbers, false, 'Generate line numbers.'
       option :line_numbers_div, false, 'Generate line numbers with wrapping divs.'
       option :start_line, 1, 'Start the line numbering (if enabled) at the desired integer'

diff --git a/lib/middleman-syntax/highlighter.rb b/lib/middleman-syntax/highlighter.rb
@@ -7,10 +7,42 @@ module Highlighter
 
       # A helper module for highlighting code
       def self.highlight(code, language=nil, opts={})
-        lexer = Rouge::Lexer.find_fancy(language, code) || Rouge::Lexers::PlainText
+        raw_lexer = Rouge::Lexer.find_fancy(language, code) || Rouge::Lexers::PlainText
+
+        if options[:escape]
+          # #reset! is normally called once by #lex, but since #lex is never
+          # called on the raw lexer, we need to call it manually. (The escape
+          # lexer only calls #continue_lex)
+          # See https://github.com/rouge-ruby/rouge/blob/a4ed658d2778a3e2d3e68873f7221b91149a2ed4/lib/rouge/lexer.rb#LL468C7-L468C13
+          # and https://github.com/rouge-ruby/rouge/blob/a4ed658d2778a3e2d3e68873f7221b91149a2ed4/lib/rouge/lexers/escape.rb#L44
+          #
+          # Otherwise you'll get weird errors w/ some lexers:
+          #
+          #   NoMethodError: undefined method `continue_lex' for nil:NilClass
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:424:in `delegate'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/lexers/jsx.rb:44:in `block (2 levels) in <class:JSX>'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:364:in `instance_exec'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:364:in `block in step'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:346:in `each'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:346:in `step'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/regex_lexer.rb:327:in `stream_tokens'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/lexer.rb:480:in `continue_lex'
+          #     ~/.asdf/installs/ruby/2.7.2/lib/ruby/gems/2.7.0/gems/rouge-3.30.0/lib/rouge/lexers/escape.rb:44:in `block in stream_tokens'
+          raw_lexer.reset!
+
+          # See https://github.com/rouge-ruby/rouge/pull/1152
+          Rouge::Formatter.enable_escape!
+          lexer = Rouge::Lexers::Escape.new(
+            start: "<!",
+            end: "!>",
+            lang: raw_lexer
+          )
+        else
+          lexer = raw_lexer
+        end
 
         highlighter_options = options.to_h.merge(opts)
-        highlighter_options[:css_class] = [ highlighter_options[:css_class], lexer.tag ].join(' ')
+        highlighter_options[:css_class] = [highlighter_options[:css_class], raw_lexer.tag].join(" ")
         lexer_options = highlighter_options.delete(:lexer_options)
 
         formatter = Middleman::Syntax::Formatters::HTML.new(highlighter_options)