middleman: Redcarpet & HAML not working correctly

Config

set :markdown_engine, :redcarpet
set :markdown, {smartypants: true, underline: true}

Haml

:markdown
  -- "foo" _bar_ *test*

In the generated HTML the markdown is processed but the custom options (underline & smartypants in this example) aren’t applied. Markdown files work fine, it just doesn’t work within the :markdown HAML filter.

module Haml::Filters
  module Markdown
    include Base
    def render text
      md_options = {smartypants: true, underline: true}
      x = Redcarpet::Render::SmartyHTML.new md_options
      y = Redcarpet::Markdown.new x, md_options
      y.render text
    end
  end
end

This change I’m currently using adds the options, but isn’t using middleman’s custom RedcarpetTemplate which has many useful changes: https://github.com/middleman/middleman/blob/v3-stable/middleman-core/lib/middleman-core/renderers/redcarpet.rb and supports stuff like middleman-syntax within the markdown.

I think what’s happening by default is something like this:

module Haml::Filters
  module Markdown
    include Base
    def render text
      ::Tilt['markdown'].new{ text }.render
    end
  end
end

But for some reason this isn’t applying the custom options.