Add WatcherFilesystemEvent.

Author: davidmorgan

pkgs/watcher/lib/src/directory_watcher/linux.dart

@@ -12,6 +12,7 @@ import '../path_set.dart';
 import '../resubscribable.dart';
 import '../utils.dart';
 import '../watch_event.dart';
+import '../watcher_filesystem_event.dart';
 
 /// Uses the inotify subsystem to watch for filesystem events.
 ///
@@ -145,7 +146,7 @@ class _LinuxDirectoryWatcher
   }
 
   /// The callback that's run when a batch of changes comes in.
-  void _onBatch(List<FileSystemEvent> batch) {
+  void _onBatch(List<WatcherFilesystemEvent> batch) {
     var files = <String>{};
     var dirs = <String>{};
     var changed = <String>{};
@@ -162,15 +163,15 @@ class _LinuxDirectoryWatcher
 
       changed.add(event.path);
 
-      if (event is FileSystemMoveEvent) {
+      if (event.isMove) {
         files.remove(event.path);
         dirs.remove(event.path);
 
         var destination = event.destination;
         if (destination == null) continue;
 
         changed.add(destination);
-        if (event.isDirectory) {
+        if (event.isDirectory!) {
           files.remove(destination);
           dirs.add(destination);
         } else {
@@ -180,7 +181,7 @@ class _LinuxDirectoryWatcher
       } else if (event is FileSystemDeleteEvent) {
         files.remove(event.path);
         dirs.remove(event.path);
-      } else if (event.isDirectory) {
+      } else if (event.isDirectory!) {
         files.remove(event.path);
         dirs.add(event.path);
       } else {

pkgs/watcher/lib/src/directory_watcher/mac_os.dart

@@ -12,6 +12,7 @@ import '../path_set.dart';
 import '../resubscribable.dart';
 import '../utils.dart';
 import '../watch_event.dart';
+import '../watcher_filesystem_event.dart';
 
 /// Uses the FSEvents subsystem to watch for filesystem events.
 ///
@@ -63,7 +64,7 @@ class _MacOSDirectoryWatcher
   ///
   /// This is separate from [_listSubscriptions] because this stream
   /// occasionally needs to be resubscribed in order to work around issue 14849.
-  StreamSubscription<List<FileSystemEvent>>? _watchSubscription;
+  StreamSubscription<List<WatcherFilesystemEvent>>? _watchSubscription;
 
   /// The subscription to the [Directory.list] call for the initial listing of
   /// the directory to determine its initial state.
@@ -109,7 +110,7 @@ class _MacOSDirectoryWatcher
   }
 
   /// The callback that's run when [Directory.watch] emits a batch of events.
-  void _onBatch(List<FileSystemEvent> batch) {
+  void _onBatch(List<WatcherFilesystemEvent> batch) {
     // If we get a batch of events before we're ready to begin emitting events,
     // it's probable that it's a batch of pre-watcher events (see issue 14373).
     // Ignore those events and re-list the directory.
@@ -184,8 +185,9 @@ class _MacOSDirectoryWatcher
   ///
   /// The returned events won't contain any [FileSystemMoveEvent]s, nor will it
   /// contain any events relating to [path].
-  Map<String, Set<FileSystemEvent>> _sortEvents(List<FileSystemEvent> batch) {
-    var eventsForPaths = <String, Set<FileSystemEvent>>{};
+  Map<String, Set<WatcherFilesystemEvent>> _sortEvents(
+      List<WatcherFilesystemEvent> batch) {
+    var eventsForPaths = <String, Set<WatcherFilesystemEvent>>{};
 
     // FSEvents can report past events, including events on the root directory
     // such as it being created. We want to ignore these. If the directory is
@@ -196,22 +198,18 @@ class _MacOSDirectoryWatcher
     // 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 <String>{};
-      if (event is FileSystemMoveEvent) {
-        var destination = event.destination;
-        if (destination != null) {
-          return {event.path, destination};
-        }
-      }
-      return {event.path};
+      if (event.isDirectory == false) return <String>{};
+      return event.paths;
     }));
 
     bool isInModifiedDirectory(String path) =>
         directories.any((dir) => path != dir && p.isWithin(dir, path));
 
-    void addEvent(String path, FileSystemEvent event) {
+    void addEvent(String path, WatcherFilesystemEvent event) {
       if (isInModifiedDirectory(path)) return;
-      eventsForPaths.putIfAbsent(path, () => <FileSystemEvent>{}).add(event);
+      eventsForPaths
+          .putIfAbsent(path, () => <WatcherFilesystemEvent>{})
+          .add(event);
     }
 
     for (var event in batch) {
@@ -233,29 +231,29 @@ class _MacOSDirectoryWatcher
   /// 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) {
+  WatcherFilesystemEvent? _canonicalEvent(Set<WatcherFilesystemEvent> 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 isDirectory = 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;
+      if (isDirectory != 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) {
+      if (event.isModify) {
         hadModifyEvent = true;
         continue;
       }
-      assert(event is FileSystemCreateEvent || event is FileSystemDeleteEvent);
+      assert(event.isCreate || event.isDelete);
 
       // 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.
@@ -285,12 +283,14 @@ class _MacOSDirectoryWatcher
         // that the directory was moved and then re-created.
         // [_eventsBasedOnFileSystem] will handle this correctly by producing a
         // DELETE event followed by a CREATE event if the directory exists.
-        if (isDir) return null;
-        return FileSystemCreateEvent(batch.first.path, false);
+        if (isDirectory!) return null;
+        return WatcherFilesystemEvent.create(batch.first.path,
+            isDirectory: false);
       case FileSystemEvent.delete:
-        return FileSystemDeleteEvent(batch.first.path, isDir);
+        return WatcherFilesystemEvent.delete(batch.first.path);
       case FileSystemEvent.modify:
-        return FileSystemModifyEvent(batch.first.path, isDir, false);
+        return WatcherFilesystemEvent.modify(batch.first.path,
+            isDirectory: isDirectory!);
       default:
         throw StateError('unreachable');
     }

pkgs/watcher/lib/src/file_watcher/native.dart

@@ -9,6 +9,7 @@ import '../file_watcher.dart';
 import '../resubscribable.dart';
 import '../utils.dart';
 import '../watch_event.dart';
+import '../watcher_filesystem_event.dart';
 
 /// Uses the native file system notifications to watch for filesystem events.
 ///
@@ -33,7 +34,7 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
   Future<void> get ready => _readyCompleter.future;
   final _readyCompleter = Completer<void>();
 
-  StreamSubscription<List<FileSystemEvent>>? _subscription;
+  StreamSubscription<List<WatcherFilesystemEvent>>? _subscription;
 
   /// On MacOS only, whether the file existed on startup.
   bool? _existedAtStartup;
@@ -65,8 +66,8 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
         onError: _eventsController.addError, onDone: _onDone);
   }
 
-  void _onBatch(List<FileSystemEvent> batch) {
-    if (batch.any((event) => event.type == FileSystemEvent.delete)) {
+  void _onBatch(List<WatcherFilesystemEvent> batch) {
+    if (batch.any((event) => event.isDelete)) {
       // If the file is deleted, the underlying stream will close. We handle
       // emitting our own REMOVE event in [_onDone].
       return;
@@ -76,8 +77,7 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
       // On MacOS, a spurious `create` event can be received for a file that is
       // created just before the `watch`. If the file existed at startup then it
       // should be ignored.
-      if (_existedAtStartup! &&
-          batch.every((event) => event.type == FileSystemEvent.create)) {
+      if (_existedAtStartup! && batch.every((event) => event.isCreate)) {
         return;
       }
     }

pkgs/watcher/lib/src/utils.dart

@@ -6,6 +6,8 @@ import 'dart:async';
 import 'dart:collection';
 import 'dart:io';
 
+import 'watcher_filesystem_event.dart';
+
 /// Returns `true` if [error] is a [FileSystemException] for a missing
 /// directory.
 bool isDirectoryNotFoundException(Object error) {
@@ -20,19 +22,19 @@ bool isDirectoryNotFoundException(Object error) {
 Set<T> unionAll<T>(Iterable<Set<T>> sets) =>
     sets.fold(<T>{}, (union, set) => union.union(set));
 
-extension BatchEvents<T> on Stream<T> {
+extension BatchEvents on Stream<FileSystemEvent> {
   /// Batches all events that are sent at the same time.
   ///
   /// When multiple events are synchronously added to a stream controller, the
   /// [StreamController] implementation uses [scheduleMicrotask] to schedule the
   /// asynchronous firing of each event. In order to recreate the synchronous
   /// batches, this collates all the events that are received in "nearby"
   /// microtasks.
-  Stream<List<T>> batchEvents() {
-    var batch = Queue<T>();
-    return StreamTransformer<T, List<T>>.fromHandlers(
-        handleData: (event, sink) {
-      batch.add(event);
+  Stream<List<WatcherFilesystemEvent>> batchEvents() {
+    var batch = Queue<WatcherFilesystemEvent>();
+    return StreamTransformer<FileSystemEvent,
+        List<WatcherFilesystemEvent>>.fromHandlers(handleData: (event, sink) {
+      batch.add(WatcherFilesystemEvent(event));
 
       // [Timer.run] schedules an event that runs after any microtasks that have
       // been scheduled.

pkgs/watcher/lib/src/watcher_filesystem_event.dart

@@ -0,0 +1,38 @@
+// Copyright (c) 2025, 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.
+
+import 'dart:io';
+
+extension type WatcherFilesystemEvent(FileSystemEvent event) {
+  bool get isDelete => type == FileSystemEvent.delete;
+  bool get isCreate => type == FileSystemEvent.create;
+  bool get isModify => type == FileSystemEvent.modify;
+  bool get isMove => type == FileSystemEvent.move;
+
+  String get path => event.path;
+  String? get destination =>
+      isMove ? (event as FileSystemMoveEvent).destination : null;
+  bool? get isDirectory => isDelete ? null : event.isDirectory;
+  int get type => event.type;
+  Set<String> get paths => {event.path, if (destination != null) destination!};
+
+  static WatcherFilesystemEvent create(String path,
+          {required bool isDirectory}) =>
+      WatcherFilesystemEvent(FileSystemCreateEvent(path, isDirectory));
+
+  static WatcherFilesystemEvent delete(String path) =>
+      WatcherFilesystemEvent(FileSystemDeleteEvent(
+          path,
+          // `FileSystemDeleteEvent` just discards `isDirectory`, nothing to pass
+          // here.
+          false));
+
+  static WatcherFilesystemEvent modify(String path,
+          {required bool isDirectory}) =>
+      WatcherFilesystemEvent(FileSystemModifyEvent(
+          path,
+          isDirectory,
+          // `contentChanged` is not used by `package:watcher`, don't set it.
+          false));
+}

pkgs/watcher/pubspec.yaml

@@ -7,7 +7,7 @@ repository: https://github.com/dart-lang/tools/tree/main/pkgs/watcher
 issue_tracker: https://github.com/dart-lang/tools/labels/package%3Awatcher
 
 environment:
-  sdk: ^3.1.0
+  sdk: ^3.3.0
 
 dependencies:
   async: ^2.5.0

pkgs/watcher/test/directory_watcher/shared.dart

@@ -138,7 +138,7 @@ void sharedTests() {
       renameFile('from.txt', 'to.txt');
       await inAnyOrder([isRemoveEvent('from.txt'), isModifyEvent('to.txt')]);
     }, onPlatform: {
-      'windows': const Skip('https://github.com/dart-lang/watcher/issues/125')
+      //'windows': const Skip('https://github.com/dart-lang/watcher/issues/125')
     });
   });
 
@@ -281,7 +281,7 @@ void sharedTests() {
         isAddEvent('new')
       ]);
     }, onPlatform: {
-      'windows': const Skip('https://github.com/dart-lang/watcher/issues/21')
+      // 'windows': const Skip('https://github.com/dart-lang/watcher/issues/21')
     });
 
     test('emits events for many nested files added at once', () async {