Fix bugs where events could be added after watchers were closed.

lib/src/directory_watcher/mac_os.dart

 // Copyright (c) 2013, 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.directory_watcher.mac_os;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 51 matching lines @@
   /// The subscription to the stream returned by [Directory.watch].
   ///
   /// This is separate from [_subscriptions] because this stream occasionally
   /// needs to be resubscribed in order to work around issue 14849.
   StreamSubscription<FileSystemEvent> _watchSubscription;
 
   /// The subscription to the [Directory.list] call for the initial listing of
   /// the directory to determine its initial state.
   StreamSubscription<FileSystemEntity> _initialListSubscription;
 
-  /// The subscription to the [Directory.list] call for listing the contents of
-  /// a subdirectory that was moved into the watched directory.
-  StreamSubscription<FileSystemEntity> _listSubscription;
+  /// The subscriptions to [Directory.list] calls for listing the contents of a
+  /// subdirectory that was moved into the watched directory.
+  final _listSubscriptions = new Set<StreamSubscription<FileSystemEntity>>();
 
   /// The timer for tracking how long we wait for an initial batch of bogus
   /// events (see issue 14373).
   Timer _bogusEventTimer;
 
   _MacOSDirectoryWatcher(String directory, int parentId)
       : directory = directory,
         _files = new PathSet(directory),
         _id = "$parentId/${_count++}" {
     _startWatch();
@@ skipping 21 matching lines @@
       _readyCompleter.complete();
     });
   }
 
   void close() {
     if (MacOSDirectoryWatcher.logDebugInfo) {
       print("[$_id] watcher is closed\n${new Chain.current().terse}");
     }
     if (_watchSubscription != null) _watchSubscription.cancel();
     if (_initialListSubscription != null) _initialListSubscription.cancel();
-    if (_listSubscription != null) _listSubscription.cancel();
     _watchSubscription = null;
     _initialListSubscription = null;
-    _listSubscription = null;
+
+    for (var subscription in _listSubscriptions) {
+      subscription.cancel();
+    }
+    _listSubscriptions.clear();
+
     _eventsController.close();
   }
 
   /// The callback that's run when [Directory.watch] emits a batch of events.
   void _onBatch(List<FileSystemEvent> batch) {
     if (MacOSDirectoryWatcher.logDebugInfo) {
       print("[$_id] ======== batch:");
       for (var event in batch) {
         print("[$_id]   ${_formatEvent(event)}");
       }
@@ skipping 54 matching lines @@
             // that happened prior to the watch beginning.
             if (_files.contains(path)) continue;
 
             _emitEvent(ChangeType.ADD, path);
             _files.add(path);
             continue;
           }
 
           if (_files.containsDir(path)) continue;
 
-          var stream = Chain.track(new Directory(path).list(recursive: true));
-          _listSubscription = stream.listen((entity) {
+          var subscription;
+          subscription = Chain.track(new Directory(path).list(recursive: true))
+              .listen((entity) {
             if (entity is Directory) return;
             if (_files.contains(path)) return;
 
             _emitEvent(ChangeType.ADD, entity.path);
             _files.add(entity.path);
           }, onError: (e, stackTrace) {
             if (MacOSDirectoryWatcher.logDebugInfo) {
               print("[$_id] got error listing $relativePath: $e");
             }
             _emitError(e, stackTrace);
+          }, onDone: () {
+            _listSubscriptions.remove(subscription);
           }, cancelOnError: true);
+          _listSubscriptions.add(subscription);
         } else if (event is FileSystemModifyEvent) {
           assert(!event.isDirectory);
           _emitEvent(ChangeType.MODIFY, path);
         } else {
           assert(event is FileSystemDeleteEvent);
           for (var removedPath in _files.remove(path)) {
             _emitEvent(ChangeType.REMOVE, removedPath);
           }
         }
       }
@@ skipping 271 matching lines @@
     } else if (event is FileSystemDeleteEvent) {
       return "delete $type $path";
     } else if (event is FileSystemModifyEvent) {
       return "modify $type $path";
     } else if (event is FileSystemMoveEvent) {
       return "move $type $path to "
           "${p.relative(event.destination, from: directory)}";
     }
   }
 }