For when you want to get the source for an expression

ugly_input_reconsumption.rb

class RawAttribute  < Parslet::Atoms::Base
  attr_reader :slice
  def initialize(slice)
    super()

    @slice = slice
  end
  
  def apply(source, context, consume_all)
    succ(@slice)
  end
  
  def to_s_inner(prec)
    "RawAttribute:#{slice}"
  end

end

def collect_raw_as name, &block
                        any.present?.capture(:start) >>
                        block.call >>
                       dynamic {|s,c|
                                 old_pos = s.pos; s.pos = c.captures[:start].offset
                                 RawAttribute.new(s.consume(old_pos - s.pos))
                                }.as(name)

end