Clearly denote adapter interface for file reloading

activesupport/lib/active_support.rb

@@ -36,8 +36,9 @@ module ActiveSupport
   autoload :DescendantsTracker
   autoload :ExecutionWrapper
   autoload :Executor
-  autoload :FileUpdateChecker
-  autoload :EventedFileUpdateChecker
+  autoload :FileUpdateMonitor
+  autoload :FileUpdateChecker, 'active_support/file_update_monitor/classic'
+  autoload :EventedFileUpdateChecker, 'active_support/file_update_monitor/evented'
   autoload :LogSubscriber
   autoload :Notifications
   autoload :Reloader

activesupport/lib/active_support/file_update_monitor.rb

@@ -0,0 +1,62 @@
+module ActiveSupport
+  module FileUpdateMonitor
+    autoload :Classic, 'active_support/file_update_monitor/classic'
+    autoload :Evented, 'active_support/file_update_monitor/evented'
+
+    # FileUpdateMonitor::Base 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 latest watched files and 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.
+    #
+    # This class is used by Rails to reload the I18n framework whenever
+    # they are changed upon a new request.
+    #
+    #   i18n_reloader = ActiveSupport::FileUpdateMonitor::Base.new(paths) do
+    #     I18n.reload!
+    #   end
+    #
+    #   ActiveSupport::Reloader.to_prepare do
+    #     i18n_reloader.execute_if_updated
+    #   end
+    class Base
+      # 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. The array of files and list of directories cannot be changed
+      # after the object has been initialized.
+      def initialize(files, dirs = {}, &block)
+        raise NotImplementedError
+      end
+
+      # Executes the given block
+      def execute
+        raise NotImplementedError
+      end
+
+      # Execute the block given if updated
+      def execute_if_updated
+        raise NotImplementedError
+      end
+
+      # Check if any of the entries were updated
+      def updated?
+        raise NotImplementedError
+      end
+    end
+  end
+end