def full_gem_path
    # TODO: try to get rid of this... or the awkward
    # TODO: also, shouldn't it default to full_name if it hasn't been written?
    return @full_gem_path if defined?(@full_gem_path) && @full_gem_path

    @full_gem_path = File.expand_path File.join(gems_dir, full_name)

    return @full_gem_path if File.directory? @full_gem_path

    @full_gem_path = File.expand_path File.join(gems_dir, original_name)
  end
#
The full path to the gem (install path + full name).