File watcher: ignore directories, allow watching non-recursively (#49150)

Author: tmat

src/BuiltInTools/dotnet-watch/DotNetWatcher.cs

@@ -79,7 +79,7 @@ public override async Task WatchAsync(CancellationToken shutdownCancellationToke
                 using var combinedCancellationSource = CancellationTokenSource.CreateLinkedTokenSource(shutdownCancellationToken, currentRunCancellationSource.Token);
                 using var fileSetWatcher = new FileWatcher(Context.Reporter);
 
-                fileSetWatcher.WatchContainingDirectories(evaluationResult.Files.Keys);
+                fileSetWatcher.WatchContainingDirectories(evaluationResult.Files.Keys, includeSubdirectories: true);
 
                 var processTask = ProcessRunner.RunAsync(processSpec, Context.Reporter, isUserApplication: true, launchResult: null, combinedCancellationSource.Token);
 

src/BuiltInTools/dotnet-watch/HotReloadDotNetWatcher.cs

@@ -180,7 +180,7 @@ public override async Task WatchAsync(CancellationToken shutdownCancellationToke
                         return;
                     }
 
-                    fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys);
+                    fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys, includeSubdirectories: true);
 
                     var changedFilesAccumulator = ImmutableList<ChangedPath>.Empty;
 
@@ -441,7 +441,7 @@ async Task<ImmutableList<ChangedFile>> CaptureChangedFilesSnapshot(ImmutableDict
                                 evaluationResult = await EvaluateRootProjectAsync(iterationCancellationToken);
 
                                 // additional directories may have been added:
-                                fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys);
+                                fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys, includeSubdirectories: true);
 
                                 await compilationHandler.Workspace.UpdateProjectConeAsync(RootFileSetFactory.RootProjectFile, iterationCancellationToken);
 
@@ -554,7 +554,7 @@ private async ValueTask WaitForFileChangeBeforeRestarting(FileWatcher fileWatche
             {
                 if (!fileWatcher.WatchingDirectories)
                 {
-                    fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys);
+                    fileWatcher.WatchContainingDirectories(evaluationResult.Files.Keys, includeSubdirectories: true);
                 }
 
                 _ = await fileWatcher.WaitForFileChangeAsync(
@@ -564,8 +564,8 @@ private async ValueTask WaitForFileChangeBeforeRestarting(FileWatcher fileWatche
             }
             else
             {
-                // evaluation cancelled - watch for any changes in the directory containing the root project:
-                fileWatcher.WatchContainingDirectories([RootFileSetFactory.RootProjectFile]);
+                // evaluation cancelled - watch for any changes in the directory tree containing the root project:
+                fileWatcher.WatchContainingDirectories([RootFileSetFactory.RootProjectFile], includeSubdirectories: true);
 
                 _ = await fileWatcher.WaitForFileChangeAsync(
                     acceptChange: change => AcceptChange(change),
@@ -605,12 +605,6 @@ private bool AcceptChange(ChangedPath change)
         {
             var (path, kind) = change;
 
-            // only handle file changes:
-            if (Directory.Exists(path))
-            {
-                return false;
-            }
-
             if (PathUtilities.GetContainingDirectories(path).FirstOrDefault(IsHiddenDirectory) is { } containingHiddenDir)
             {
                 Context.Reporter.Report(MessageDescriptor.IgnoringChangeInHiddenDirectory, containingHiddenDir, kind, path);

src/BuiltInTools/dotnet-watch/Internal/FileWatcher.cs

@@ -5,8 +5,13 @@ namespace Microsoft.DotNet.Watch
 {
     internal sealed class FileWatcher(IReporter reporter) : IDisposable
     {
-        // Directory watcher for each watched directory
-        private readonly Dictionary<string, IDirectoryWatcher> _watchers = [];
+        // Directory watcher for each watched directory tree.
+        // Keyed by full path to the root directory with a trailing directory separator.
+        private readonly Dictionary<string, IDirectoryWatcher> _directoryTreeWatchers = new(PathUtilities.OSSpecificPathComparer);
+
+        // Directory watcher for each watched directory (non-recursive).
+        // Keyed by full path to the root directory with a trailing directory separator.
+        private readonly Dictionary<string, IDirectoryWatcher> _directoryWatchers = new(PathUtilities.OSSpecificPathComparer);
 
         private bool _disposed;
         public event Action<ChangedPath>? OnFileChange;
@@ -22,7 +27,7 @@ public void Dispose()
 
             _disposed = true;
 
-            foreach (var (_, watcher) in _watchers)
+            foreach (var (_, watcher) in _directoryTreeWatchers)
             {
                 watcher.OnFileChange -= WatcherChangedHandler;
                 watcher.OnError -= WatcherErrorHandler;
@@ -31,39 +36,33 @@ public void Dispose()
         }
 
         public bool WatchingDirectories
-            => _watchers.Count > 0;
+            => _directoryTreeWatchers.Count > 0 || _directoryWatchers.Count > 0;
 
-        public void WatchContainingDirectories(IEnumerable<string> filePaths)
-            => WatchDirectories(filePaths.Select(path => Path.GetDirectoryName(path)!));
+        public void WatchContainingDirectories(IEnumerable<string> filePaths, bool includeSubdirectories)
+            => WatchDirectories(filePaths.Select(path => Path.GetDirectoryName(path)!), includeSubdirectories);
 
-        public void WatchDirectories(IEnumerable<string> directories)
+        public void WatchDirectories(IEnumerable<string> directories, bool includeSubdirectories)
         {
             ObjectDisposedException.ThrowIf(_disposed, this);
 
-            foreach (var dir in directories)
+            foreach (var dir in directories.Distinct())
             {
-                var directory = EnsureTrailingSlash(dir);
-
-                var alreadyWatched = _watchers
-                    .Where(d => directory.StartsWith(d.Key))
-                    .Any();
+                var directory = PathUtilities.EnsureTrailingSlash(PathUtilities.NormalizeDirectorySeparators(dir));
 
-                if (alreadyWatched)
+                // the directory is watched by active directory watcher:
+                if (!includeSubdirectories && _directoryWatchers.ContainsKey(directory))
                 {
                     continue;
                 }
 
-                var redundantWatchers = _watchers
-                    .Where(d => d.Key.StartsWith(directory))
-                    .Select(d => d.Key)
-                    .ToList();
-
-                foreach (var watcher in redundantWatchers)
+                // the directory is a root or subdirectory of active directory tree watcher:
+                var alreadyWatched = _directoryTreeWatchers.Any(d => directory.StartsWith(d.Key, PathUtilities.OSSpecificPathComparison));
+                if (alreadyWatched)
                 {
-                    DisposeWatcher(watcher);
+                    continue;
                 }
 
-                var newWatcher = FileWatcherFactory.CreateWatcher(directory);
+                var newWatcher = FileWatcherFactory.CreateWatcher(directory, includeSubdirectories);
                 if (newWatcher is EventBasedDirectoryWatcher eventBasedWatcher)
                 {
                     eventBasedWatcher.Logger = message => reporter.Verbose(message);
@@ -73,7 +72,30 @@ public void WatchDirectories(IEnumerable<string> directories)
                 newWatcher.OnError += WatcherErrorHandler;
                 newWatcher.EnableRaisingEvents = true;
 
-                _watchers.Add(directory, newWatcher);
+                // watchers that are now redundant (covered by the new directory watcher):
+                if (includeSubdirectories)
+                {
+                    var watchersToRemove = _directoryTreeWatchers
+                        .Where(d => d.Key.StartsWith(directory, PathUtilities.OSSpecificPathComparison))
+                        .ToList();
+
+                    foreach (var (watchedDirectory, watcher) in watchersToRemove)
+                    {
+                        _directoryTreeWatchers.Remove(watchedDirectory);
+
+                        watcher.EnableRaisingEvents = false;
+                        watcher.OnFileChange -= WatcherChangedHandler;
+                        watcher.OnError -= WatcherErrorHandler;
+
+                        watcher.Dispose();
+                    }
+
+                    _directoryTreeWatchers.Add(directory, newWatcher);
+                }
+                else
+                {
+                    _directoryWatchers.Add(directory, newWatcher);
+                }
             }
         }
 
@@ -93,21 +115,6 @@ private void WatcherChangedHandler(object? sender, ChangedPath change)
             }
         }
 
-        private void DisposeWatcher(string directory)
-        {
-            var watcher = _watchers[directory];
-            _watchers.Remove(directory);
-
-            watcher.EnableRaisingEvents = false;
-            watcher.OnFileChange -= WatcherChangedHandler;
-            watcher.OnError -= WatcherErrorHandler;
-
-            watcher.Dispose();
-        }
-
-        private static string EnsureTrailingSlash(string path)
-            => (path is [.., var last] && last != Path.DirectorySeparatorChar) ? path + Path.DirectorySeparatorChar : path;
-
         public async Task<ChangedFile?> WaitForFileChangeAsync(IReadOnlyDictionary<string, FileItem> fileSet, Action? startedWatching, CancellationToken cancellationToken)
         {
             var changedPath = await WaitForFileChangeAsync(
@@ -151,7 +158,7 @@ public static async ValueTask WaitForFileChangeAsync(string filePath, IReporter
         {
             using var watcher = new FileWatcher(reporter);
 
-            watcher.WatchDirectories([Path.GetDirectoryName(filePath)!]);
+            watcher.WatchContainingDirectories([filePath], includeSubdirectories: false);
 
             var fileChange = await watcher.WaitForFileChangeAsync(
                 acceptChange: change => change.Path == filePath,

src/BuiltInTools/dotnet-watch/Internal/FileWatcher/EventBasedDirectoryWatcher.cs

@@ -8,22 +8,21 @@ namespace Microsoft.DotNet.Watch
     internal sealed class EventBasedDirectoryWatcher : IDirectoryWatcher
     {
         public event EventHandler<ChangedPath>? OnFileChange;
-
         public event EventHandler<Exception>? OnError;
 
         public string WatchedDirectory { get; }
-
-        internal Action<string>? Logger { get; set; }
+        public bool IncludeSubdirectories { get; }
+        public Action<string>? Logger { get; set; }
 
         private volatile bool _disposed;
-
         private FileSystemWatcher? _fileSystemWatcher;
+        private readonly Lock _createLock = new();
 
-        private readonly object _createLock = new();
-
-        internal EventBasedDirectoryWatcher(string watchedDirectory)
+        internal EventBasedDirectoryWatcher(string watchedDirectory, bool includeSubdirectories)
         {
             WatchedDirectory = watchedDirectory;
+            IncludeSubdirectories = includeSubdirectories;
+
             CreateFileSystemWatcher();
         }
 
@@ -40,7 +39,7 @@ private void WatcherErrorHandler(object sender, ErrorEventArgs e)
                 return;
             }
 
-            Logger?.Invoke("Error");
+            Logger?.Invoke("[FW] Error");
 
             var exception = e.GetException();
 
@@ -65,21 +64,23 @@ private void WatcherRenameHandler(object sender, RenamedEventArgs e)
                 return;
             }
 
-            Logger?.Invoke($"Renamed '{e.OldFullPath}' to '{e.FullPath}'.");
-
-            NotifyChange(e.OldFullPath, ChangeKind.Delete);
-            NotifyChange(e.FullPath, ChangeKind.Add);
+            Logger?.Invoke($"[FW] Renamed '{e.OldFullPath}' to '{e.FullPath}'.");
 
             if (Directory.Exists(e.FullPath))
             {
-                foreach (var newLocation in Directory.EnumerateFileSystemEntries(e.FullPath, "*", SearchOption.AllDirectories))
+                foreach (var newLocation in Directory.EnumerateFiles(e.FullPath, "*", SearchOption.AllDirectories))
                 {
                     // Calculated previous path of this moved item.
                     var oldLocation = Path.Combine(e.OldFullPath, newLocation.Substring(e.FullPath.Length + 1));
                     NotifyChange(oldLocation, ChangeKind.Delete);
                     NotifyChange(newLocation, ChangeKind.Add);
                 }
             }
+            else
+            {
+                NotifyChange(e.OldFullPath, ChangeKind.Delete);
+                NotifyChange(e.FullPath, ChangeKind.Add);
+            }
         }
 
         private void WatcherDeletedHandler(object sender, FileSystemEventArgs e)
@@ -89,7 +90,16 @@ private void WatcherDeletedHandler(object sender, FileSystemEventArgs e)
                 return;
             }
 
-            Logger?.Invoke($"Deleted '{e.FullPath}'.");
+            var isDir = Directory.Exists(e.FullPath);
+
+            Logger?.Invoke($"[FW] Deleted '{e.FullPath}'.");
+
+            // ignore directory changes:
+            if (isDir)
+            {
+                return;
+            }
+
             NotifyChange(e.FullPath, ChangeKind.Delete);
         }
 
@@ -100,7 +110,16 @@ private void WatcherChangeHandler(object sender, FileSystemEventArgs e)
                 return;
             }
 
-            Logger?.Invoke($"Updated  '{e.FullPath}'.");
+            var isDir = Directory.Exists(e.FullPath);
+
+            Logger?.Invoke($"[FW] Updated '{e.FullPath}'.");
+
+            // ignore directory changes:
+            if (isDir)
+            {
+                return;
+            }
+
             NotifyChange(e.FullPath, ChangeKind.Update);
         }
 
@@ -111,7 +130,15 @@ private void WatcherAddedHandler(object sender, FileSystemEventArgs e)
                 return;
             }
 
-            Logger?.Invoke($"Added  '{e.FullPath}'.");
+            var isDir = Directory.Exists(e.FullPath);
+
+            Logger?.Invoke($"[FW] Added '{e.FullPath}'.");
+
+            if (isDir)
+            {
+                return;
+            }
+
             NotifyChange(e.FullPath, ChangeKind.Add);
         }
 
@@ -136,7 +163,7 @@ private void CreateFileSystemWatcher()
 
                 _fileSystemWatcher = new FileSystemWatcher(WatchedDirectory)
                 {
-                    IncludeSubdirectories = true
+                    IncludeSubdirectories = IncludeSubdirectories
                 };
 
                 _fileSystemWatcher.Created += WatcherAddedHandler;

src/BuiltInTools/dotnet-watch/Internal/FileWatcher/FileWatcherFactory.cs

@@ -5,14 +5,14 @@ namespace Microsoft.DotNet.Watch
 {
     internal static class FileWatcherFactory
     {
-        public static IDirectoryWatcher CreateWatcher(string watchedDirectory)
-            => CreateWatcher(watchedDirectory, EnvironmentVariables.IsPollingEnabled);
+        public static IDirectoryWatcher CreateWatcher(string watchedDirectory, bool includeSubdirectories)
+            => CreateWatcher(watchedDirectory, EnvironmentVariables.IsPollingEnabled, includeSubdirectories);
 
-        public static IDirectoryWatcher CreateWatcher(string watchedDirectory, bool usePollingWatcher)
+        public static IDirectoryWatcher CreateWatcher(string watchedDirectory, bool usePollingWatcher, bool includeSubdirectories)
         {
             return usePollingWatcher ?
-                new PollingDirectoryWatcher(watchedDirectory) :
-                new EventBasedDirectoryWatcher(watchedDirectory);
+                new PollingDirectoryWatcher(watchedDirectory, includeSubdirectories) :
+                new EventBasedDirectoryWatcher(watchedDirectory, includeSubdirectories);
         }
     }
 }

src/BuiltInTools/dotnet-watch/Internal/FileWatcher/IDirectoryWatcher.cs

@@ -1,16 +1,18 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace Microsoft.DotNet.Watch
+namespace Microsoft.DotNet.Watch;
+
+/// <summary>
+/// Watches for changes in a <see cref="WatchedDirectory"/> and its subdirectories.
+/// </summary>
+internal interface IDirectoryWatcher : IDisposable
 {
-    internal interface IDirectoryWatcher : IDisposable
-    {
-        event EventHandler<ChangedPath> OnFileChange;
+    event EventHandler<ChangedPath> OnFileChange;
 
-        event EventHandler<Exception> OnError;
+    event EventHandler<Exception> OnError;
 
-        string WatchedDirectory { get; }
+    string WatchedDirectory { get; }
 
-        bool EnableRaisingEvents { get; set; }
-    }
+    bool EnableRaisingEvents { get; set; }
 }