strategies are not dispoable anymore but can be cleaned. Make LiveVirtualStrategy is faster.

Author: AnakinRaW

src/PetroglyphTools/PG.StarWarsGame.Engine.FileSystem/IO/FileExistStrategies/FileExistsStrategy.cs

@@ -4,11 +4,11 @@
 
 namespace PG.StarWarsGame.Engine.IO.FileExistStrategies;
 
-internal abstract class FileExistsStrategy(IFileSystem fileSystem) : IDisposable
+internal abstract class FileExistsStrategy(IFileSystem fileSystem)
 {
     protected readonly IFileSystem FileSystem = fileSystem;
 
     public abstract bool FileExists(ReadOnlySpan<char> baseDirectory, ref ValueStringBuilder stringBuilder);
 
-    public virtual void Dispose() { }
+    internal virtual void Cleanup() { }
 }

src/PetroglyphTools/PG.StarWarsGame.Engine.FileSystem/IO/FileExistStrategies/LiveVirtualFileExistsStrategy.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.IO;
 using System.IO.Abstractions;
 using AnakinRaW.CommonUtilities.FileSystem;
@@ -13,8 +13,7 @@ internal sealed class LiveVirtualFileExistsStrategy(IFileSystem fileSystem, File
     private const int WatcherBufferSize = 64 * 1024;
 
     private readonly object _watchersLock = new();
-    private readonly Dictionary<string, IFileSystemWatcher> _watchers = new(StringComparer.OrdinalIgnoreCase);
-    private bool _disposed;
+    private readonly ConcurrentDictionary<string, IFileSystemWatcher> _watchers = new(StringComparer.OrdinalIgnoreCase);
 
     public override bool FileExists(ReadOnlySpan<char> baseDirectory, ref ValueStringBuilder stringBuilder)
     {
@@ -23,18 +22,37 @@ public override bool FileExists(ReadOnlySpan<char> baseDirectory, ref ValueStrin
         return base.FileExists(baseDirectory, ref stringBuilder);
     }
 
+    internal override void Cleanup()
+    {
+        IFileSystemWatcher[] watchers;
+        lock (_watchersLock)
+        {
+            watchers = new IFileSystemWatcher[_watchers.Count];
+            _watchers.Values.CopyTo(watchers, 0);
+            _watchers.Clear();
+        }
+
+        foreach (var watcher in watchers)
+            TearDownWatcher(watcher);
+
+        base.Cleanup();
+    }
+
     private void EnsureWatcher(ReadOnlySpan<char> baseDirectory)
     {
-        if (_disposed)
+        var rootStr = baseDirectory.ToString();
+
+        // Fast path: already watching this directory — lockless, no OS call.
+        if (_watchers.ContainsKey(rootStr))
             return;
 
-        var rootStr = baseDirectory.ToString();
+        // Only pay for the Directory.Exists syscall when the watcher might be missing.
         if (!FileSystem.Directory.Exists(rootStr))
             return;
 
         lock (_watchersLock)
         {
-            if (_disposed || _watchers.ContainsKey(rootStr))
+            if (_watchers.ContainsKey(rootStr))
                 return;
 
             var watcher = FileSystem.FileSystemWatcher.New(rootStr);
@@ -53,25 +71,6 @@ private void EnsureWatcher(ReadOnlySpan<char> baseDirectory)
         }
     }
 
-    public override void Dispose()
-    {
-        IFileSystemWatcher[] watchers;
-        lock (_watchersLock)
-        {
-            if (_disposed)
-                return;
-            _disposed = true;
-            watchers = new IFileSystemWatcher[_watchers.Count];
-            _watchers.Values.CopyTo(watchers, 0);
-            _watchers.Clear();
-        }
-
-        foreach (var watcher in watchers)
-            TearDownWatcher(watcher);
-
-        base.Dispose();
-    }
-
     private void OnFileEvent(object sender, FileSystemEventArgs e)
     {
         InvalidatePathAndSubtree(e.FullPath);
@@ -89,8 +88,6 @@ private void OnWatcherError(object sender, ErrorEventArgs e)
         string? brokenRoot = null;
         lock (_watchersLock)
         {
-            if (_disposed)
-                return;
             foreach (var kv in _watchers)
             {
                 if (ReferenceEquals(kv.Value, sender))
@@ -102,7 +99,7 @@ private void OnWatcherError(object sender, ErrorEventArgs e)
             }
             if (broken is null)
                 return;
-            _watchers.Remove(brokenRoot!);
+            _watchers.TryRemove(brokenRoot!, out _);
         }
 
         ClearCacheUnder(brokenRoot!);

src/PetroglyphTools/PG.StarWarsGame.Engine.FileSystem/IO/FileExistStrategies/VirtualFileExistsStrategyBase.cs

@@ -15,10 +15,10 @@ internal abstract class VirtualFileExistsStrategyBase(IFileSystem fileSystem, Fi
 
     protected readonly FileExistsStrategy Underlying = underlying;
 
-    public override void Dispose()
+    internal override void Cleanup()
     {
         Store.Clear();
-        Underlying.Dispose();
+        Underlying.Cleanup();
     }
 
     public override bool FileExists(ReadOnlySpan<char> baseDirectory, ref ValueStringBuilder stringBuilder)

src/PetroglyphTools/PG.StarWarsGame.Engine.FileSystem/IO/PetroglyphFileSystem.Strategies.cs

@@ -8,6 +8,15 @@ public sealed partial class PetroglyphFileSystem
 {
     private FileExistsStrategy _strategy;
 
+    internal void CleanupStrategy() => _strategy.Cleanup();
+
+    private FileExistsStrategy CreateDefaultStrategy()
+    {
+        return RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+            ? new WindowsFileExistsStrategy(_underlyingFileSystem)
+            : new VirtualFileExistsStrategy(_underlyingFileSystem, new WineFileExistsStrategy(_underlyingFileSystem));
+    }
+
     /// <summary>
     /// Switches the active file-exists strategy to one that issues a Win32 <c>CreateFileA</c> call per lookup.
     /// </summary>
@@ -116,6 +125,6 @@ private void SwapStrategy(FileExistsStrategy next)
     {
         var old = _strategy;
         _strategy = next;
-        old?.Dispose();
+        old.Cleanup();
     }
 }

src/PetroglyphTools/PG.StarWarsGame.Engine.FileSystem/IO/PetroglyphFileSystem.cs

@@ -4,8 +4,6 @@
 using System.IO;
 using System.IO.Abstractions;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-using PG.StarWarsGame.Engine.IO.FileExistStrategies;
 
 namespace PG.StarWarsGame.Engine.IO;
 
@@ -47,9 +45,7 @@ public PetroglyphFileSystem(IServiceProvider serviceProvider)
             throw new ArgumentNullException(nameof(serviceProvider));
         _underlyingFileSystem = serviceProvider.GetRequiredService<IFileSystem>();
 
-        _strategy = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
-            ? new WindowsFileExistsStrategy(_underlyingFileSystem)
-            : new VirtualFileExistsStrategy(_underlyingFileSystem, new WineFileExistsStrategy(_underlyingFileSystem));
+        _strategy = CreateDefaultStrategy();
     }
 
     /// <summary>