require "set" require "pathname" require "concurrent/atomic/atomic_boolean" module ActiveSupport # Allows you to "listen" to changes in a file system. # The evented file updater does not hit disk when checking for updates # instead it uses platform specific file system events to trigger a change # in state. # # The file checker takes an array of files to watch or a hash specifying directories # and file extensions to watch. It also takes a block that is called when # EventedFileUpdateChecker#execute is run or when EventedFileUpdateChecker#execute_if_updated # is run and there have been changes to the file system. # # Note: Forking will cause the first call to `updated?` to return `true`. # # Example: # # checker = EventedFileUpdateChecker.new(["/tmp/foo"], -> { puts "changed" }) # checker.updated? # # => false # checker.execute_if_updated # # => nil # # FileUtils.touch("/tmp/foo") # # checker.updated? # # => true # checker.execute_if_updated # # => "changed" # class EventedFileUpdateChecker #:nodoc: all def initialize(files, dirs = {}, &block) @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 if (@dtw = directories_to_watch).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 begin 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 end boot! end def updated? @boot_mutex.synchronize do if @pid != Process.pid boot! @pid = Process.pid @updated.make_true end end @updated.true? end def execute @updated.make_false @block.call end def execute_if_updated if updated? yield if block_given? execute true end end private def boot! Listen.to(*@dtw, &method(:changed)).start end def changed(modified, added, removed) unless updated? @updated.make_true if (modified + added + removed).any? { |f| watching?(f) } end end def watching?(file) file = @ph.xpath(file) if @files.member?(file) true elsif file.directory? false else ext = @ph.normalize_extension(file.extname) file.dirname.ascend do |dir| if @dirs.fetch(dir, []).include?(ext) break true elsif dir == @lcsp || dir.root? break false end end end end def directories_to_watch dtw = (@files + @dirs.keys).map { |f| @ph.existing_parent(f) } dtw.compact! dtw.uniq! @ph.filter_out_descendants(dtw) end class PathHelper def xpath(path) Pathname.new(path).expand_path end def normalize_extension(ext) ext.to_s.sub(/\A\./, "") end # Given a collection of Pathname objects returns the longest subpath # common to all of them, or +nil+ if there is none. def longest_common_subpath(paths) return if paths.empty? lcsp = Pathname.new(paths[0]) paths[1..-1].each do |path| until ascendant_of?(lcsp, path) if lcsp.root? # If we get here a root directory is not an ascendant of path. # This may happen if there are paths in different drives on # Windows. return else lcsp = lcsp.parent end end end lcsp end # Returns the deepest existing ascendant, which could be the argument itself. def existing_parent(dir) dir.ascend do |ascendant| break ascendant if ascendant.directory? end end # Filters out directories which are descendants of others in the collection (stable). def filter_out_descendants(dirs) return dirs if dirs.length < 2 dirs_sorted_by_nparts = dirs.sort_by { |dir| dir.each_filename.to_a.length } descendants = [] until dirs_sorted_by_nparts.empty? dir = dirs_sorted_by_nparts.shift dirs_sorted_by_nparts.reject! do |possible_descendant| ascendant_of?(dir, possible_descendant) && descendants << possible_descendant end end # Array#- preserves order. dirs - descendants end private def ascendant_of?(base, other) base != other && other.ascend do |ascendant| break true if base == ascendant end end end end end