Sinatra + Sinatra::Sprockets + rails-asset.org + append paths

config.ru

require 'find'

map "/#{Sinatra::Sprockets.config.prefix}" do
  env = Sinatra::Sprockets.environment

  installed_assets = Bundler.definition.resolve.select {|e|
    e.name =~ /^rails-assets/
  }.map {|e|
    spec = e.instance_variable_get(:@specification)
    [spec.name, spec.version].join('-')
  }

  if installed_assets.size > 0

    bundle_root = File.join(
                       Bundler.root,
                       Bundler.settings.instance_variable_get(:@local_config)['BUNDLE_PATH'],
                       Bundler.ruby_scope,
                       'gems'
                       )

    assets_parent_dir = "vendor/assets"

    Find.find(bundle_root) {|path|
      next unless File.directory?(path)
      next unless installed_assets.include?(File.basename(path))

      %w(javascripts stylesheets images fonts).each {|asset|
        assets_dir = File.join(path, assets_parent_dir, asset)
        if File.directory?(assets_dir) and !env.paths.include?(assets_dir)
          env.append_path assets_dir
          Find.prune
        end
      }
    }
  end

  env.append_path "assets/javascripts"
  env.append_path "assets/stylesheets"

  run env
end