class Opal::CliRunners::Compiler

def files_to_directories
  directories = @files.map { |file| File.dirname(file) }.uniq
  previous_dir = nil
  # Only get the topmost directories
  directories = directories.sort.map do |dir|
    if previous_dir && dir.start_with?(previous_dir + '/')
      nil
    else
      previous_dir = dir
    end
  end
  directories.compact
end