class Rails::BacktraceCleaner

def add_gem_filters
  return unless defined?(Gem)
  gems_paths = (Gem.path + [Gem.default_dir]).uniq.map!{ |p| Regexp.escape(p) }
  return if gems_paths.empty?
  gems_regexp = %r{(#{gems_paths.join('|')})/gems/([^/]+)-([\w\.]+)/(.*)}
  add_filter { |line| line.sub(gems_regexp, '\2 (\3) \4') }
end

def initialize
  super
  add_filter   { |line| line.sub("#{Rails.root}/", '') }
  add_filter   { |line| line.sub(RENDER_TEMPLATE_PATTERN, '') }
  add_filter   { |line| line.sub('./', '/') } # for tests
  add_gem_filters
  add_silencer { |line| line !~ APP_DIRS_PATTERN }
end