Roll Observatory packages and add a roll script

watcher/lib/src/file_watcher/native.dart

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library watcher.file_watcher.native;
-
-import 'dart:async';
-import 'dart:io';
-
-import '../file_watcher.dart';
-import '../resubscribable.dart';
-import '../utils.dart';
-import '../watch_event.dart';
-
-/// Uses the native file system notifications to watch for filesystem events.
-///
-/// Single-file notifications are much simpler than those for multiple files, so
-/// this doesn't need to be split out into multiple OS-specific classes.
-class NativeFileWatcher extends ResubscribableWatcher implements FileWatcher {
-  NativeFileWatcher(String path)
-      : super(path, () => new _NativeFileWatcher(path));
-}
-
-class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
-  final String path;
-
-  Stream<WatchEvent> get events => _eventsController.stream;
-  final _eventsController = new StreamController<WatchEvent>.broadcast();
-
-  bool get isReady => _readyCompleter.isCompleted;
-
-  Future get ready => _readyCompleter.future;
-  final _readyCompleter = new Completer();
-
-  StreamSubscription _subscription;
-
-  _NativeFileWatcher(this.path) {
-    _listen();
-
-    // We don't need to do any initial set-up, so we're ready immediately after
-    // being listened to.
-    _readyCompleter.complete();
-  }
-
-  void _listen() {
-    // Batch the events together so that we can dedup them.
-    _subscription = new File(path).watch()
-        .transform(new BatchedStreamTransformer<FileSystemEvent>())
-        .listen(_onBatch, onError: _eventsController.addError, onDone: _onDone);
-  }
-
-  void _onBatch(List<FileSystemEvent> batch) {
-    if (batch.any((event) => event.type == FileSystemEvent.DELETE)) {
-      // If the file is deleted, the underlying stream will close. We handle
-      // emitting our own REMOVE event in [_onDone].
-      return;
-    }
-
-    _eventsController.add(new WatchEvent(ChangeType.MODIFY, path));
-  }
-
-  _onDone() async {
-    var fileExists = await new File(path).exists();
-
-    // Check for this after checking whether the file exists because it's
-    // possible that [close] was called between [File.exists] being called and
-    // it completing.
-    if (_eventsController.isClosed) return;
-
-    if (fileExists) {
-      // If the file exists now, it was probably removed and quickly replaced;
-      // this can happen for example when another file is moved on top of it.
-      // Re-subscribe and report a modify event.
-      _eventsController.add(new WatchEvent(ChangeType.MODIFY, path));
-      _listen();
-    } else {
-      _eventsController.add(new WatchEvent(ChangeType.REMOVE, path));
-      close();
-    }
-  }
-
-  void close() {
-    if (_subscription != null) _subscription.cancel();
-    _subscription = null;
-    _eventsController.close();
-  }
-}