From f15eb9d8ad8c997e4fa664f34740f32c2a42204d Mon Sep 17 00:00:00 2001
From: David Morgan <davidmorgan@google.com>
Date: Mon, 29 Sep 2025 13:35:43 +0200
Subject: [PATCH 1/2] Add test coverage around startup race and missing file on
 startup.

---
 pkgs/watcher/test/file_watcher/startup_race_tests.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/watcher/test/file_watcher/startup_race_tests.dart b/pkgs/watcher/test/file_watcher/startup_race_tests.dart
index 59e4f8e7b..37814e1ab 100644
--- a/pkgs/watcher/test/file_watcher/startup_race_tests.dart
+++ b/pkgs/watcher/test/file_watcher/startup_race_tests.dart
@@ -31,7 +31,7 @@ void startupRaceTests({required bool isNative}) {
     // TODO(davidmorgan): the MacOS watcher currently does get unwanted events,
     // fix it.
     if (isNative && Platform.isMacOS) {
-      expect(events, greaterThan(10));
+      expect(events, greaterThan(50));
     } else {
       expect(events, 0);
     }

From c69889e8d19f3e05ac8a0ffe719268bdc179d5d1 Mon Sep 17 00:00:00 2001
From: David Morgan <davidmorgan@google.com>
Date: Mon, 29 Sep 2025 16:15:36 +0200
Subject: [PATCH 2/2] Fix unwanted file modify event on MacOS on startup.

---
 pkgs/watcher/CHANGELOG.md                     |  7 ++++
 pkgs/watcher/lib/src/file_watcher/native.dart | 36 +++++++++++++++----
 pkgs/watcher/pubspec.yaml                     |  2 +-
 .../test/file_watcher/startup_race_tests.dart | 11 +-----
 4 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/pkgs/watcher/CHANGELOG.md b/pkgs/watcher/CHANGELOG.md
index 562c2e587..686126dc1 100644
--- a/pkgs/watcher/CHANGELOG.md
+++ b/pkgs/watcher/CHANGELOG.md
@@ -1,3 +1,10 @@
+## 1.1.5-wip
+
+- Bug fix: with `FileWatcher` on MacOS, a modify event was sometimes reported if
+  the file was created immediately before the watcher was created. Now, if the
+  file exists when the watcher is created then this modify event is not sent.
+  This matches the Linux native and polling (Windows) watchers.
+
 ## 1.1.4
 
 - Improve handling of subdirectories: ignore `PathNotFoundException` due to
diff --git a/pkgs/watcher/lib/src/file_watcher/native.dart b/pkgs/watcher/lib/src/file_watcher/native.dart
index 502aa1095..28cf8a180 100644
--- a/pkgs/watcher/lib/src/file_watcher/native.dart
+++ b/pkgs/watcher/lib/src/file_watcher/native.dart
@@ -35,6 +35,9 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
 
   StreamSubscription<List<FileSystemEvent>>? _subscription;
 
+  /// On MacOS only, whether the file existed on startup.
+  bool? _existedAtStartup;
+
   _NativeFileWatcher(this.path) {
     _listen();
 
@@ -43,12 +46,23 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
     _readyCompleter.complete();
   }
 
-  void _listen() {
-    // Batch the events together so that we can dedup them.
-    _subscription = File(path)
-        .watch()
-        .batchEvents()
-        .listen(_onBatch, onError: _eventsController.addError, onDone: _onDone);
+  void _listen() async {
+    var file = File(path);
+
+    // Batch the events together so that we can dedupe them.
+    var stream = file.watch().batchEvents();
+
+    if (Platform.isMacOS) {
+      var existedAtStartupFuture = file.exists();
+      // Delay processing watch events until the existence check finishes.
+      stream = stream.asyncMap((event) async {
+        _existedAtStartup ??= await existedAtStartupFuture;
+        return event;
+      });
+    }
+
+    _subscription = stream.listen(_onBatch,
+        onError: _eventsController.addError, onDone: _onDone);
   }
 
   void _onBatch(List<FileSystemEvent> batch) {
@@ -58,6 +72,16 @@ class _NativeFileWatcher implements FileWatcher, ManuallyClosedWatcher {
       return;
     }
 
+    if (Platform.isMacOS) {
+      // 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)) {
+        return;
+      }
+    }
+
     _eventsController.add(WatchEvent(ChangeType.MODIFY, path));
   }
 
diff --git a/pkgs/watcher/pubspec.yaml b/pkgs/watcher/pubspec.yaml
index eff642fe5..c7119052d 100644
--- a/pkgs/watcher/pubspec.yaml
+++ b/pkgs/watcher/pubspec.yaml
@@ -1,5 +1,5 @@
 name: watcher
-version: 1.1.4
+version: 1.1.5-wip
 description: >-
   A file system watcher. It monitors changes to contents of directories and
   sends notifications when files have been added, removed, or modified.
diff --git a/pkgs/watcher/test/file_watcher/startup_race_tests.dart b/pkgs/watcher/test/file_watcher/startup_race_tests.dart
index 37814e1ab..50f5328f6 100644
--- a/pkgs/watcher/test/file_watcher/startup_race_tests.dart
+++ b/pkgs/watcher/test/file_watcher/startup_race_tests.dart
@@ -2,8 +2,6 @@
 // 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';
-
 import 'package:test/test.dart';
 
 import '../utils.dart';
@@ -27,13 +25,6 @@ void startupRaceTests({required bool isNative}) {
       );
     }
     await Future.wait(futures);
-
-    // TODO(davidmorgan): the MacOS watcher currently does get unwanted events,
-    // fix it.
-    if (isNative && Platform.isMacOS) {
-      expect(events, greaterThan(50));
-    } else {
-      expect(events, 0);
-    }
+    expect(events, 0);
   });
 }