Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/watcher/src/directory_watcher/windows.dart

+// Copyright (c) 2014, 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.
+// TODO(rnystrom): Merge with mac_os version.
+
+library watcher.directory_watcher.windows;
+
+import 'dart:async';
+import 'dart:collection';
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:stack_trace/stack_trace.dart';
+
+import '../constructable_file_system_event.dart';
+import '../path_set.dart';
+import '../utils.dart';
+import '../watch_event.dart';
+import 'resubscribable.dart';
+
+class WindowsDirectoryWatcher extends ResubscribableDirectoryWatcher {
+  WindowsDirectoryWatcher(String directory)
+      : super(directory, () => new _WindowsDirectoryWatcher(directory));
+}
+
+class _EventBatcher {
+  static const Duration _BATCH_DELAY = const Duration(milliseconds: 100);
+  final List<FileSystemEvent> events = [];
+  Timer timer;
+
+  void addEvent(FileSystemEvent event, void callback()) {
+    events.add(event);
+    if (timer != null) {
+      timer.cancel();
+    }
+    timer = new Timer(_BATCH_DELAY, callback);
+  }
+
+  void cancelTimer() {
+    timer.cancel();
+  }
+}
+
+class _WindowsDirectoryWatcher implements ManuallyClosedDirectoryWatcher {
+  final String directory;
+
+  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();
+
+  final Map<String, _EventBatcher> _eventBatchers =
+      new HashMap<String, _EventBatcher>();
+
+  /// The set of files that are known to exist recursively within the watched
+  /// directory.
+  ///
+  /// The state of files on the filesystem is compared against this to determine
+  /// the real change that occurred. This is also used to emit REMOVE events
+  /// when subdirectories are moved out of the watched directory.
+  final PathSet _files;
+
+  /// The subscription to the stream returned by [Directory.watch].
+  StreamSubscription<FileSystemEvent> _watchSubscription;
+
+  /// The subscription to the stream returned by [Directory.watch] of the
+  /// parent directory to [directory]. This is needed to detect changes to
+  /// [directory], as they are not included on Windows.
+  StreamSubscription<FileSystemEvent> _parentWatchSubscription;
+
+  /// The subscription to the [Directory.list] call for the initial listing of
+  /// the directory to determine its initial state.
+  StreamSubscription<FileSystemEntity> _initialListSubscription;
+
+  /// The subscriptions to the [Directory.list] calls for listing the contents
+  /// of subdirectories that were moved into the watched directory.
+  final Set<StreamSubscription<FileSystemEntity>> _listSubscriptions
+      = new HashSet<StreamSubscription<FileSystemEntity>>();
+
+  _WindowsDirectoryWatcher(String directory)
+      : directory = directory, _files = new PathSet(directory) {
+    // Before we're ready to emit events, wait for [_listDir] to complete.
+    _listDir().then((_) {
+      _startWatch();
+      _startParentWatcher();
+      _readyCompleter.complete();
+    });
+  }
+
+  void close() {
+    if (_watchSubscription != null) _watchSubscription.cancel();
+    if (_parentWatchSubscription != null) _parentWatchSubscription.cancel();
+    if (_initialListSubscription != null) _initialListSubscription.cancel();
+    for (var sub in _listSubscriptions) {
+      sub.cancel();
+    }
+    _listSubscriptions.clear();
+    for (var batcher in _eventBatchers.values) {
+      batcher.cancelTimer();
+    }
+    _eventBatchers.clear();
+    _watchSubscription = null;
+    _parentWatchSubscription = null;
+    _initialListSubscription = null;
+    _eventsController.close();
+  }
+
+  /// On Windows, if [directory] is deleted, we will not receive any event.
+  ///
+  /// Instead, we add a watcher on the parent folder (if any), that can notify
+  /// us about [directory]. This also includes events such as moves.
+  void _startParentWatcher() {
+    var absoluteDir = p.absolute(directory);
+    var parent = p.dirname(absoluteDir);
+    // Check if [directory] is already the root directory.
+    if (FileSystemEntity.identicalSync(parent, directory)) return;
+    var parentStream = Chain.track(
+        new Directory(parent).watch(recursive: false));
+    _parentWatchSubscription = parentStream.listen((event) {
+      // Only look at events for 'directory'.
+      if (p.basename(event.path) != p.basename(absoluteDir)) return;
+      // Test if the directory is removed. FileSystemEntity.typeSync will
+      // return NOT_FOUND if it's unable to decide upon the type, including
+      // access denied issues, which may happen when the directory is deleted.
+      // FileSystemMoveEvent and FileSystemDeleteEvent events will always mean
+      // the directory is now gone.
+      if (event is FileSystemMoveEvent ||
+          event is FileSystemDeleteEvent ||
+          (FileSystemEntity.typeSync(directory) ==
+           FileSystemEntityType.NOT_FOUND)) {
+        for (var path in _files.toSet()) {
+          _emitEvent(ChangeType.REMOVE, path);
+        }
+        _files.clear();
+        close();
+      }
+    }, onError: (error) {
+      // Ignore errors, simply close the stream. The user listens on
+      // [directory], and while it can fail to listen on the parent, we may
+      // still be able to listen on the path requested.
+      _parentWatchSubscription.cancel();
+      _parentWatchSubscription = null;
+    });
+  }
+
+  void _onEvent(FileSystemEvent event) {
+    assert(isReady);
+    final batcher = _eventBatchers.putIfAbsent(
+        event.path, () => new _EventBatcher());
+    batcher.addEvent(event, () {
+      _eventBatchers.remove(event.path);
+      _onBatch(batcher.events);
+    });
+  }
+
+  /// The callback that's run when [Directory.watch] emits a batch of events.
+  void _onBatch(List<FileSystemEvent> batch) {
+    _sortEvents(batch).forEach((path, events) {
+      var relativePath = p.relative(path, from: directory);
+
+      var canonicalEvent = _canonicalEvent(events);
+      events = canonicalEvent == null ?
+          _eventsBasedOnFileSystem(path) : [canonicalEvent];
+
+      for (var event in events) {
+        if (event is FileSystemCreateEvent) {
+          if (!event.isDirectory) {
+            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));
+          var sub;
+          sub = stream.listen((entity) {
+            if (entity is Directory) return;
+            if (_files.contains(path)) return;
+
+            _emitEvent(ChangeType.ADD, entity.path);
+            _files.add(entity.path);
+          }, onDone: () {
+            _listSubscriptions.remove(sub);
+          }, onError: (e, stackTrace) {
+            _listSubscriptions.remove(sub);
+            _emitError(e, stackTrace);
+          }, cancelOnError: true);
+          _listSubscriptions.add(sub);
+        } else if (event is FileSystemModifyEvent) {
+          if (!event.isDirectory) {
+            _emitEvent(ChangeType.MODIFY, path);
+          }
+        } else {
+          assert(event is FileSystemDeleteEvent);
+          for (var removedPath in _files.remove(path)) {
+            _emitEvent(ChangeType.REMOVE, removedPath);
+          }
+        }
+      }
+    });
+  }
+
+  /// Sort all the events in a batch into sets based on their path.
+  ///
+  /// A single input event may result in multiple events in the returned map;
+  /// for example, a MOVE event becomes a DELETE event for the source and a
+  /// CREATE event for the destination.
+  ///
+  /// The returned events won't contain any [FileSystemMoveEvent]s, nor will it
+  /// contain any events relating to [directory].
+  Map<String, Set<FileSystemEvent>> _sortEvents(List<FileSystemEvent> batch) {
+    var eventsForPaths = {};
+
+    // Events within directories that already have events are superfluous; the
+    // directory's full contents will be examined anyway, so we ignore such
+    // events. Emitting them could cause useless or out-of-order events.
+    var directories = unionAll(batch.map((event) {
+      if (!event.isDirectory) return new Set();
+      if (event is! FileSystemMoveEvent) return new Set.from([event.path]);
+      return new Set.from([event.path, event.destination]);
+    }));
+
+    isInModifiedDirectory(path) =>
+        directories.any((dir) => path != dir && path.startsWith(dir));
+
+    addEvent(path, event) {
+      if (isInModifiedDirectory(path)) return;
+      var set = eventsForPaths.putIfAbsent(path, () => new Set());
+      set.add(event);
+    }
+
+    for (var event in batch) {
+      if (event is FileSystemMoveEvent) {
+        addEvent(event.destination, event);
+      }
+      addEvent(event.path, event);
+    }
+
+    return eventsForPaths;
+  }
+
+  /// Returns the canonical event from a batch of events on the same path, if
+  /// one exists.
+  ///
+  /// If [batch] doesn't contain any contradictory events (e.g. DELETE and
+  /// CREATE, or events with different values for [isDirectory]), this returns a
+  /// single event that describes what happened to the path in question.
+  ///
+  /// If [batch] does contain contradictory events, this returns `null` to
+  /// indicate that the state of the path on the filesystem should be checked to
+  /// determine what occurred.
+  FileSystemEvent _canonicalEvent(Set<FileSystemEvent> batch) {
+    // An empty batch indicates that we've learned earlier that the batch is
+    // contradictory (e.g. because of a move).
+    if (batch.isEmpty) return null;
+
+    var type = batch.first.type;
+    var isDir = batch.first.isDirectory;
+    var hadModifyEvent = false;
+
+    for (var event in batch.skip(1)) {
+      // If one event reports that the file is a directory and another event
+      // doesn't, that's a contradiction.
+      if (isDir != event.isDirectory) return null;
+
+      // Modify events don't contradict either CREATE or REMOVE events. We can
+      // safely assume the file was modified after a CREATE or before the
+      // REMOVE; otherwise there will also be a REMOVE or CREATE event
+      // (respectively) that will be contradictory.
+      if (event is FileSystemModifyEvent) {
+        hadModifyEvent = true;
+        continue;
+      }
+      assert(event is FileSystemCreateEvent ||
+             event is FileSystemDeleteEvent ||
+             event is FileSystemMoveEvent);
+
+      // If we previously thought this was a MODIFY, we now consider it to be a
+      // CREATE or REMOVE event. This is safe for the same reason as above.
+      if (type == FileSystemEvent.MODIFY) {
+        type = event.type;
+        continue;
+      }
+
+      // A CREATE event contradicts a REMOVE event and vice versa.
+      assert(type == FileSystemEvent.CREATE ||
+             type == FileSystemEvent.DELETE ||
+             type == FileSystemEvent.MOVE);
+      if (type != event.type) return null;
+    }
+
+    switch (type) {
+      case FileSystemEvent.CREATE:
+        return new ConstructableFileSystemCreateEvent(batch.first.path, isDir);
+      case FileSystemEvent.DELETE:
+        return new ConstructableFileSystemDeleteEvent(batch.first.path, isDir);
+      case FileSystemEvent.MODIFY:
+        return new ConstructableFileSystemModifyEvent(
+            batch.first.path, isDir, false);
+      case FileSystemEvent.MOVE:
+        return null;
+      default: assert(false);
+    }
+  }
+
+  /// Returns one or more events that describe the change between the last known
+  /// state of [path] and its current state on the filesystem.
+  ///
+  /// This returns a list whose order should be reflected in the events emitted
+  /// to the user, unlike the batched events from [Directory.watch]. The
+  /// returned list may be empty, indicating that no changes occurred to [path]
+  /// (probably indicating that it was created and then immediately deleted).
+  List<FileSystemEvent> _eventsBasedOnFileSystem(String path) {
+    var fileExisted = _files.contains(path);
+    var dirExisted = _files.containsDir(path);
+    var fileExists = new File(path).existsSync();
+    var dirExists = new Directory(path).existsSync();
+
+    var events = [];
+    if (fileExisted) {
+      if (fileExists) {
+        events.add(new ConstructableFileSystemModifyEvent(path, false, false));
+      } else {
+        events.add(new ConstructableFileSystemDeleteEvent(path, false));
+      }
+    } else if (dirExisted) {
+      if (dirExists) {
+        // If we got contradictory events for a directory that used to exist and
+        // still exists, we need to rescan the whole thing in case it was
+        // replaced with a different directory.
+        events.add(new ConstructableFileSystemDeleteEvent(path, true));
+        events.add(new ConstructableFileSystemCreateEvent(path, true));
+      } else {
+        events.add(new ConstructableFileSystemDeleteEvent(path, true));
+      }
+    }
+
+    if (!fileExisted && fileExists) {
+      events.add(new ConstructableFileSystemCreateEvent(path, false));
+    } else if (!dirExisted && dirExists) {
+      events.add(new ConstructableFileSystemCreateEvent(path, true));
+    }
+
+    return events;
+  }
+
+  /// The callback that's run when the [Directory.watch] stream is closed.
+  /// Note that this is unlikely to happen on Windows, unless the system itself
+  /// closes the handle.
+  void _onDone() {
+    _watchSubscription = null;
+
+    // Emit remove events for any remaining files.
+    for (var file in _files.toSet()) {
+      _emitEvent(ChangeType.REMOVE, file);
+    }
+    _files.clear();
+    close();
+  }
+
+  /// Start or restart the underlying [Directory.watch] stream.
+  void _startWatch() {
+    // Batch the events together so that we can dedup events.
+    var innerStream =
+        Chain.track(new Directory(directory).watch(recursive: true));
+    _watchSubscription = innerStream.listen(_onEvent,
+        onError: _eventsController.addError,
+        onDone: _onDone);
+  }
+
+  /// Starts or restarts listing the watched directory to get an initial picture
+  /// of its state.
+  Future _listDir() {
+    assert(!isReady);
+    if (_initialListSubscription != null) _initialListSubscription.cancel();
+
+    _files.clear();
+    var completer = new Completer();
+    var stream = Chain.track(new Directory(directory).list(recursive: true));
+    void handleEntity(entity) {
+      if (entity is! Directory) _files.add(entity.path);
+    }
+    _initialListSubscription = stream.listen(
+        handleEntity,
+        onError: _emitError,
+        onDone: completer.complete,
+        cancelOnError: true);
+    return completer.future;
+  }
+
+  /// Emit an event with the given [type] and [path].
+  void _emitEvent(ChangeType type, String path) {
+    if (!isReady) return;
+
+    _eventsController.add(new WatchEvent(type, path));
+  }
+
+  /// Emit an error, then close the watcher.
+  void _emitError(error, StackTrace stackTrace) {
+    _eventsController.addError(error, stackTrace);
+    close();
+  }
+}