I emailed the Buildr developer mailing list and someone told me to look here for inspiration. Turns out that the relevant code snippet is ...
module TocFilter
def toc(input)
output = "<ol class=\"toc\">"
input.scan(/<(h2)(?:>|\s+(.*?)>)([^<]*)<\/\1\s*>/mi).each do |entry|
id = (entry[1][/^id=(['"])(.*)\1$/, 2] rescue nil)
title = entry[2].gsub(/<(\w*).*?>(.*?)<\/\1\s*>/m, '\2').strip
if id
output << %{<li><a href="##{id}">#{title}</a></li>}
else
output << %{<li>#{title}</li>}
end
end
output << '</ol>'
output
end
end
Liquid::Template.register_filter(TocFilter)
Make a folder in the source folder of your site called _plugins
and then paste this code into a file called TocFilter.rb
within that folder.
It works!!