Roda plugin to easily support (and prefer) trailing slashes in certain paths.

rodaplugin_redirect_to_slash.rb

# frozen-string-literal: true

class Roda
  module RodaPlugins
    # Treats any string matchers with a trailing slash ("/") almost like
    # the slash wasn't there, but GET requests to that path without the
    # slash are redirected to the path with a trailing slash.
    # 
    # Example:
    #
    #   route do |r|
    #     r.is "a/" do
    #       "path is #{r.path}"
    #     end
    #   end
    #
    #   # with redirect_to_slash:
    #   # GET /a   => browser gets redirected to /a/
    #   # GET /a/  => browser gets the response "path is /a/"
    #   # POST /a  => browser gets the response "path is /a"
    #   # POST /a/ => browser gets the response "path is /a/"
    module RedirectToSlash
      module RequestMethods
        private

        def match(str)
          if String === str
            # trailing slash?
            if str[-1] == "/"
              # try the normal matcher without the slash
              return false unless _match_string(str.chop)

              # let's say the matcher was "a/", we accept both "/a" and "/a/"
              if @remaining_path == "/"
                # consume the trailing slash from the path so that TERM can match
                @remaining_path = ""
              elsif @remaining_path == "" && is_get?
                # but if the path ends with "/a" and it's a GET request,
                # redirect to "/a/"
                redirect(path + "/")
              end
              return true

            end
            
            # no trailing slash, call the normal matcher
            _match_string(str)

          else
            super(str)
          end
        end
          
      end
    end

    register_plugin(:redirect_to_slash, RedirectToSlash)
  end
end