require "active_support/core_ext/array/wrap" require "active_support/core_ext/array/extract_options" module ActiveSupport # \FileUpdateChecker specifies the API used by Rails to watch files # and control reloading. The API depends on four methods: # # * +initialize+ which expects two parameters and one block as # described below; # # * +updated?+ which returns a boolean if there were updates in # the filesystem or not; # # * +execute+ which executes the given block on initialization # and updates the counter to the latest timestamp; # # * +execute_if_updated+ which just executes the block if it was updated; # # After initialization, a call to +execute_if_updated+ must execute # the block only if there was really a change in the filesystem. # # == Examples # # This class is used by Rails to reload the I18n framework whenever # they are changed upon a new request. # # i18n_reloader = ActiveSupport::FileUpdateChecker.new(paths) do # I18n.reload! # end # # ActionDispatch::Reloader.to_prepare do # i18n_reloader.execute_if_updated # end # class FileUpdateChecker # It accepts two parameters on initialization. The first is an array # of files and the second is an optional hash of directories. The hash must # have directories as keys and the value is an array of extensions to be # watched under that directory. # # This method must also receive a block that will be called once a path changes. # # == Implementation details # # This particular implementation checks for added and updated files, # but not removed files. Directories lookup are compiled to a glob for # performance. Therefore, while someone can add new files to the +files+ # array after initialization (and parts of Rails do depend on this feature), # adding new directories after initialization is not allowed. # # Notice that other objects that implements FileUpdateChecker API may # not even allow new files to be added after initialization. If this # is the case, we recommend freezing the +files+ after initialization to # avoid changes that won't make effect. def initialize(files, dirs={}, &block) @files = files @glob = compile_glob(dirs) @block = block @updated_at = nil @last_update_at = updated_at end # Check if any of the entries were updated. If so, the updated_at # value is cached until the block is executed via +execute+ or +execute_if_updated+ def updated? current_updated_at = updated_at if @last_update_at < current_updated_at @updated_at = updated_at true else false end end # Executes the given block and updates the counter to latest timestamp. def execute @last_update_at = updated_at @block.call ensure @updated_at = nil end # Execute the block given if updated. def execute_if_updated if updated? execute true else false end end private def updated_at #:nodoc: @updated_at || begin all = [] all.concat @files.select { |f| File.exists?(f) } all.concat Dir[@glob] if @glob all.map { |path| File.mtime(path) }.max || Time.at(0) end end def compile_glob(hash) #:nodoc: hash.freeze # Freeze so changes aren't accidently pushed return if hash.empty? globs = [] hash.each do |key, value| globs << "#{key}/**/*#{compile_ext(value)}" end "{#{globs.join(",")}}" end def compile_ext(array) #:nodoc: array = Array.wrap(array) return if array.empty? ".{#{array.join(",")}}" end end end