new

# File activesupport/lib/active_support/evented_file_update_checker.rb, line 36
    def initialize(files, dirs = {}, &block)
      unless block
        raise ArgumentError, "A block is required to initialize an EventedFileUpdateChecker"
      end

      @ph    = PathHelper.new
      @files = files.map { |f| @ph.xpath(f) }.to_set

      @dirs = {}
      dirs.each do |dir, exts|
        @dirs[@ph.xpath(dir)] = Array(exts).map { |ext| @ph.normalize_extension(ext) }
      end

      @block      = block
      @updated    = Concurrent::AtomicBoolean.new(false)
      @lcsp       = @ph.longest_common_subpath(@dirs.keys)
      @pid        = Process.pid
      @boot_mutex = Mutex.new

      dtw = directories_to_watch
      @dtw, @missing = dtw.partition(&:exist?)

      if @dtw.any?
        # Loading listen triggers warnings. These are originated by a legit
        # usage of attr_* macros for private attributes, but adds a lot of noise
        # to our test suite. Thus, we lazy load it and disable warnings locally.
        silence_warnings do
          require "listen"
        rescue LoadError => e
          raise LoadError, "Could not load the 'listen' gem. Add `gem 'listen'` to the development group of your Gemfile", e.backtrace
        end
      end
      boot!
    end