Merge pull request dart-lang/watcher#99 from scheglov/migrate-null-safe

Migrate to null safety.

pkgs/watcher/.travis.yml

@@ -2,7 +2,6 @@ language: dart
 
 dart:
 - dev
-- 2.8.4
 
 os:
 - linux
@@ -16,9 +15,6 @@ matrix:
   include:
   - dart: dev
     dart_task: dartfmt
-  - dart: 2.8.4
-    dart_task:
-      dartanalyzer: --fatal-warnings .
   - dart: dev
     dart_task:
       dartanalyzer: --fatal-warnings --fatal-infos .

pkgs/watcher/lib/src/async_queue.dart

@@ -33,7 +33,8 @@ class AsyncQueue<T> {
   /// Used to avoid top-leveling asynchronous errors.
   final Function _errorHandler;
 
-  AsyncQueue(this._processor, {Function onError}) : _errorHandler = onError;
+  AsyncQueue(this._processor, {required Function onError})
+      : _errorHandler = onError;
 
   /// Enqueues [item] to be processed and starts asynchronously processing it
   /// if a process isn't already running.

pkgs/watcher/lib/src/custom_watcher_factory.dart

@@ -7,9 +7,9 @@ import '../watcher.dart';
 /// A factory to produce custom watchers for specific file paths.
 class _CustomWatcherFactory {
   final String id;
-  final DirectoryWatcher Function(String path, {Duration pollingDelay})
+  final DirectoryWatcher? Function(String path, {Duration? pollingDelay})
       createDirectoryWatcher;
-  final FileWatcher Function(String path, {Duration pollingDelay})
+  final FileWatcher? Function(String path, {Duration? pollingDelay})
       createFileWatcher;
 
   _CustomWatcherFactory(
@@ -22,7 +22,7 @@ class _CustomWatcherFactory {
 /// registered more than once.
 /// [createDirectoryWatcher] and [createFileWatcher] should return watchers for
 /// the file paths they are able to handle. If the custom watcher is not able to
-/// handle the path it should reuturn null.
+/// handle the path it should return null.
 /// The paths handled by each custom watch may not overlap, at most one custom
 /// matcher may return a non-null watcher for a given path.
 ///
@@ -31,9 +31,10 @@ class _CustomWatcherFactory {
 /// will be used instead of the default.
 void registerCustomWatcher(
   String id,
-  DirectoryWatcher Function(String path, {Duration pollingDelay})
+  DirectoryWatcher Function(String path, {Duration? pollingDelay})?
       createDirectoryWatcher,
-  FileWatcher Function(String path, {Duration pollingDelay}) createFileWatcher,
+  FileWatcher Function(String path, {Duration? pollingDelay})?
+      createFileWatcher,
 ) {
   if (_customWatcherFactories.containsKey(id)) {
     throw ArgumentError('A custom watcher with id `$id` '
@@ -49,10 +50,10 @@ void registerCustomWatcher(
 ///
 /// Returns `null` if no custom watcher was applicable and throws a [StateError]
 /// if more than one was.
-DirectoryWatcher createCustomDirectoryWatcher(String path,
-    {Duration pollingDelay}) {
-  DirectoryWatcher customWatcher;
-  String customFactoryId;
+DirectoryWatcher? createCustomDirectoryWatcher(String path,
+    {Duration? pollingDelay}) {
+  DirectoryWatcher? customWatcher;
+  String? customFactoryId;
   for (var watcherFactory in _customWatcherFactories.values) {
     if (customWatcher != null) {
       throw StateError('Two `CustomWatcherFactory`s applicable: '
@@ -69,9 +70,9 @@ DirectoryWatcher createCustomDirectoryWatcher(String path,
 ///
 /// Returns `null` if no custom watcher was applicable and throws a [StateError]
 /// if more than one was.
-FileWatcher createCustomFileWatcher(String path, {Duration pollingDelay}) {
-  FileWatcher customWatcher;
-  String customFactoryId;
+FileWatcher? createCustomFileWatcher(String path, {Duration? pollingDelay}) {
+  FileWatcher? customWatcher;
+  String? customFactoryId;
   for (var watcherFactory in _customWatcherFactories.values) {
     if (customWatcher != null) {
       throw StateError('Two `CustomWatcherFactory`s applicable: '

pkgs/watcher/lib/src/directory_watcher.dart

@@ -28,7 +28,7 @@ abstract class DirectoryWatcher implements Watcher {
   /// shorter will give more immediate feedback at the expense of doing more IO
   /// and higher CPU usage. Defaults to one second. Ignored for non-polling
   /// watchers.
-  factory DirectoryWatcher(String directory, {Duration pollingDelay}) {
+  factory DirectoryWatcher(String directory, {Duration? pollingDelay}) {
     if (FileSystemEntity.isWatchSupported) {
       var customWatcher =
           createCustomDirectoryWatcher(directory, pollingDelay: pollingDelay);

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

@@ -91,7 +91,7 @@ class _LinuxDirectoryWatcher
       } else {
         _files.add(entity.path);
       }
-    }, onError: (error, StackTrace stackTrace) {
+    }, onError: (Object error, StackTrace stackTrace) {
       _eventsController.addError(error, stackTrace);
       close();
     }, onDone: () {
@@ -155,13 +155,16 @@ class _LinuxDirectoryWatcher
         files.remove(event.path);
         dirs.remove(event.path);
 
-        changed.add(event.destination);
+        var destination = event.destination;
+        if (destination == null) continue;
+
+        changed.add(destination);
         if (event.isDirectory) {
-          files.remove(event.destination);
-          dirs.add(event.destination);
+          files.remove(destination);
+          dirs.add(destination);
         } else {
-          files.add(event.destination);
-          dirs.remove(event.destination);
+          files.add(destination);
+          dirs.remove(destination);
         }
       } else if (event is FileSystemDeleteEvent) {
         files.remove(event.path);
@@ -221,7 +224,7 @@ class _LinuxDirectoryWatcher
         _files.add(entity.path);
         _emit(ChangeType.ADD, entity.path);
       }
-    }, onError: (error, StackTrace stackTrace) {
+    }, onError: (Object error, StackTrace stackTrace) {
       // Ignore an exception caused by the dir not existing. It's fine if it
       // was added and then quickly removed.
       if (error is FileSystemException) return;
@@ -258,8 +261,10 @@ class _LinuxDirectoryWatcher
   /// Like [Stream.listen], but automatically adds the subscription to
   /// [_subscriptions] so that it can be canceled when [close] is called.
   void _listen<T>(Stream<T> stream, void Function(T) onData,
-      {Function onError, void Function() onDone, bool cancelOnError}) {
-    StreamSubscription subscription;
+      {Function? onError,
+      void Function()? onDone,
+      bool cancelOnError = false}) {
+    late StreamSubscription subscription;
     subscription = stream.listen(onData, onError: onError, onDone: () {
       _subscriptions.remove(subscription);
       onDone?.call();

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

@@ -64,19 +64,19 @@ 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<FileSystemEvent>>? _watchSubscription;
 
   /// The subscription to the [Directory.list] call for the initial listing of
   /// the directory to determine its initial state.
-  StreamSubscription<FileSystemEntity> _initialListSubscription;
+  StreamSubscription<FileSystemEntity>? _initialListSubscription;
 
   /// The subscriptions to [Directory.list] calls for listing the contents of a
   /// subdirectory that was moved into the watched directory.
   final _listSubscriptions = <StreamSubscription<FileSystemEntity>>{};
 
   /// The timer for tracking how long we wait for an initial batch of bogus
   /// events (see issue 14373).
-  Timer _bogusEventTimer;
+  late Timer _bogusEventTimer;
 
   _MacOSDirectoryWatcher(String path)
       : path = path,
@@ -144,18 +144,20 @@ class _MacOSDirectoryWatcher
 
           if (_files.containsDir(path)) continue;
 
-          StreamSubscription<FileSystemEntity> subscription;
-          subscription = Directory(path).list(recursive: true).listen((entity) {
+          var stream = Directory(path).list(recursive: true);
+          var subscription = stream.listen((entity) {
             if (entity is Directory) return;
             if (_files.contains(path)) return;
 
             _emitEvent(ChangeType.ADD, entity.path);
             _files.add(entity.path);
-          }, onError: (e, StackTrace stackTrace) {
-            _emitError(e, stackTrace);
-          }, onDone: () {
-            _listSubscriptions.remove(subscription);
           }, cancelOnError: true);
+          subscription.onDone(() {
+            _listSubscriptions.remove(subscription);
+          });
+          subscription.onError((Object e, StackTrace stackTrace) {
+            _emitError(e, stackTrace);
+          });
           _listSubscriptions.add(subscription);
         } else if (event is FileSystemModifyEvent) {
           assert(!event.isDirectory);
@@ -192,7 +194,10 @@ class _MacOSDirectoryWatcher
     var directories = unionAll(batch.map((event) {
       if (!event.isDirectory) return <String>{};
       if (event is FileSystemMoveEvent) {
-        return {event.path, event.destination};
+        var destination = event.destination;
+        if (destination != null) {
+          return {event.path, destination};
+        }
       }
       return {event.path};
     }));
@@ -224,7 +229,7 @@ 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) {
+  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;
@@ -394,7 +399,7 @@ class _MacOSDirectoryWatcher
   }
 
   /// Emit an error, then close the watcher.
-  void _emitError(error, StackTrace stackTrace) {
+  void _emitError(Object error, StackTrace stackTrace) {
     _eventsController.addError(error, stackTrace);
     close();
   }

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

@@ -24,7 +24,7 @@ class PollingDirectoryWatcher extends ResubscribableWatcher
   /// will pause between successive polls of the directory contents. Making this
   /// shorter will give more immediate feedback at the expense of doing more IO
   /// and higher CPU usage. Defaults to one second.
-  PollingDirectoryWatcher(String directory, {Duration pollingDelay})
+  PollingDirectoryWatcher(String directory, {Duration? pollingDelay})
       : super(directory, () {
           return _PollingDirectoryWatcher(
               directory, pollingDelay ?? Duration(seconds: 1));
@@ -56,12 +56,12 @@ class _PollingDirectoryWatcher
   /// The previous modification times of the files in the directory.
   ///
   /// Used to tell which files have been modified.
-  final _lastModifieds = <String, DateTime>{};
+  final _lastModifieds = <String, DateTime?>{};
 
   /// The subscription used while [directory] is being listed.
   ///
   /// Will be `null` if a list is not currently happening.
-  StreamSubscription<FileSystemEntity> _listSubscription;
+  StreamSubscription<FileSystemEntity>? _listSubscription;
 
   /// The queue of files waiting to be processed to see if they have been
   /// modified.
@@ -70,7 +70,10 @@ class _PollingDirectoryWatcher
   /// queue exists to let each of those proceed at their own rate. The lister
   /// will enqueue files as quickly as it can. Meanwhile, files are dequeued
   /// and processed sequentially.
-  AsyncQueue<String> _filesToProcess;
+  late final AsyncQueue<String?> _filesToProcess = AsyncQueue<String?>(
+      _processFile, onError: (Object e, StackTrace stackTrace) {
+    if (!_events.isClosed) _events.addError(e, stackTrace);
+  });
 
   /// The set of files that have been seen in the current directory listing.
   ///
@@ -79,11 +82,6 @@ class _PollingDirectoryWatcher
   final _polledFiles = <String>{};
 
   _PollingDirectoryWatcher(this.path, this._pollingDelay) {
-    _filesToProcess =
-        AsyncQueue<String>(_processFile, onError: (e, StackTrace stackTrace) {
-      if (!_events.isClosed) _events.addError(e, stackTrace);
-    });
-
     _poll();
   }
 
@@ -120,7 +118,7 @@ class _PollingDirectoryWatcher
 
       if (entity is! File) return;
       _filesToProcess.add(entity.path);
-    }, onError: (error, StackTrace stackTrace) {
+    }, onError: (Object error, StackTrace stackTrace) {
       if (!isDirectoryNotFoundException(error)) {
         // It's some unknown error. Pipe it over to the event stream so the
         // user can see it.
@@ -136,7 +134,7 @@ class _PollingDirectoryWatcher
 
   /// Processes [file] to determine if it has been modified since the last
   /// time it was scanned.
-  Future<void> _processFile(String file) async {
+  Future<void> _processFile(String? file) async {
     // `null` is the sentinel which means the directory listing is complete.
     if (file == null) {
       await _completePoll();