fix: second-pass audit — robustness, logging, null safety

High:
- AppLog.Write: wrap in try/catch to prevent recursive crash in global
  exception handlers when disk is full or log path is inaccessible
- AppLog: add log rotation (5 MB cap, rotate to .bak)

Medium:
- VsrepoService: kill elevated process tree on cancellation (RunVsrepoElevatedAsync)
- ProbeAsync: use VSRGUI_PROBE marker to extract JSON from noisy stdout
- LoadDefinitions: null-guard Packages and Releases after deserialization
- GetInstalledAsync: document assumed vsrepo column layout

Low:
- RestoreAppState: add _isRestoringState flag to prevent redundant
  FilterChanged/TargetComboBox_SelectionChanged during state restoration
- EnsureEnvironmentAsync: clear path text boxes on probe failure
- RunBusyOperationAsync: show status message when operation is skipped
- NuGet.config: remove non-portable VS offline package source

Author: Frank

MainWindow.xaml.cs

@@ -48,6 +48,7 @@ public partial class MainWindow : WpfFluentWindow
     private bool _isBusy;
     private bool _isNavigationExpanded;
     private bool _isUpdatingThemeSelection;
+    private bool _isRestoringState;
 
     private sealed record PackageCommand(string Operation, bool Force);
 
@@ -228,6 +229,10 @@ private async Task<bool> EnsureEnvironmentAsync(bool reprobe)
         }
 
         AppendLog($"Probe failed: {_lastProbe.Message}");
+        _lastPaths = null;
+        DefinitionsPathTextBox.Text = string.Empty;
+        BinariesPathTextBox.Text = string.Empty;
+        ScriptsPathTextBox.Text = string.Empty;
         return false;
     }
 
@@ -482,6 +487,19 @@ private void RestoreSelection(string? identifier)
     }
 
     private void RestoreAppState()
+    {
+        _isRestoringState = true;
+        try
+        {
+            RestoreAppStateCore();
+        }
+        finally
+        {
+            _isRestoringState = false;
+        }
+    }
+
+    private void RestoreAppStateCore()
     {
         _appState = _appStateService.Load();
         ApplyThemeSelection();
@@ -683,6 +701,7 @@ private async Task RunBusyOperationAsync(Func<Task> action, string errorContext)
     {
         if (_isBusy)
         {
+            StatusTextBlock.Text = "Operation in progress, please wait...";
             return;
         }
 
@@ -929,7 +948,7 @@ private void SearchTextBox_TextChanged(object sender, TextChangedEventArgs e)
     private void FilterChanged(object sender, SelectionChangedEventArgs e)
     {
         UpdateStatusSummarySelection();
-        if (IsLoaded)
+        if (IsLoaded && !_isRestoringState)
         {
             ApplyFilters(_selectedPackage?.Identifier);
             SaveAppState();
@@ -951,7 +970,7 @@ private void StatusSummaryButton_Click(object sender, RoutedEventArgs e)
 
     private async void TargetComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
     {
-        if (IsLoaded && !string.IsNullOrWhiteSpace(PythonPathTextBox.Text) && !_isBusy)
+        if (IsLoaded && !_isRestoringState && !string.IsNullOrWhiteSpace(PythonPathTextBox.Text) && !_isBusy)
         {
             _lastPaths = null;
             await RefreshPackagesAsync(updateDefinitions: false, reprobe: false, reloadDefinitions: false);
@@ -968,6 +987,7 @@ private async void PackagesGrid_MouseDoubleClick(object sender, MouseButtonEvent
     {
         if (_isBusy || PackagesGrid.SelectedItem is not PackageItem item)
         {
+            if (_isBusy) StatusTextBlock.Text = "Operation in progress, please wait...";
             return;
         }
 

NuGet.config

@@ -3,6 +3,5 @@
   <packageSources>
     <clear />
     <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
-    <add key="Microsoft Visual Studio Offline Packages" value="C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\" />
   </packageSources>
 </configuration>

Services/AppLog.cs

@@ -1,4 +1,4 @@
-using System.Diagnostics;
+using System.Diagnostics;
 using System.IO;
 
 namespace VSRepo_Gui.Services;
@@ -8,22 +8,51 @@ public static class AppLog
     private static readonly object SyncRoot = new();
     private static readonly string LogDirectory = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "VSRepo_Gui", "logs");
     private static readonly string LogPath = Path.Combine(LogDirectory, "latest.log");
+    private const long MaxLogSizeBytes = 5 * 1024 * 1024; // 5 MB
 
     public static string CurrentLogPath => LogPath;
 
     public static void Write(string message)
     {
-        lock (SyncRoot)
+        try
         {
-            Directory.CreateDirectory(LogDirectory);
-            File.AppendAllText(LogPath, $"[{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}] {message}{Environment.NewLine}");
+            lock (SyncRoot)
+            {
+                Directory.CreateDirectory(LogDirectory);
+                RotateIfNeeded();
+                File.AppendAllText(LogPath, $"[{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}] {message}{Environment.NewLine}");
+            }
+        }
+        catch
+        {
+            // Must never throw — this is called from global exception handlers.
+            // If logging fails (disk full, permissions), silently degrade.
+            Debug.WriteLine($"AppLog.Write failed: {message}");
         }
     }
 
     public static void Write(Exception exception, string context)
     {
         Write($"{context}: {exception}");
     }
-}
-
-
+
+    private static void RotateIfNeeded()
+    {
+        try
+        {
+            var info = new FileInfo(LogPath);
+            if (info.Exists && info.Length > MaxLogSizeBytes)
+            {
+                var bakPath = LogPath + ".bak";
+                File.Delete(bakPath);
+                File.Move(LogPath, bakPath, overwrite: true);
+            }
+        }
+        catch
+        {
+            // Best effort — don't let rotation failure block logging.
+        }
+    }
+}
+
+

Services/VsrepoService.cs

@@ -118,7 +118,7 @@ public async Task<ProbeResult> ProbeAsync(string pythonExe, CancellationToken ca
             "spec = importlib.util.find_spec('vsrepo.vsrepo')",
             "result['has_vsrepo'] = spec is not None",
             "result['vsrepo_path'] = None if spec is None else spec.origin",
-            "print(json.dumps(result))",
+            "print('VSRGUI_PROBE:' + json.dumps(result))",
         });
 
         var command = await RunProcessAsync(pythonExe, ["-c", code], cancellationToken);
@@ -127,7 +127,13 @@ public async Task<ProbeResult> ProbeAsync(string pythonExe, CancellationToken ca
             return new ProbeResult(false, command.CombinedOutput, pythonExe, false, false, null, null, null);
         }
 
-        using var document = JsonDocument.Parse(command.StdOut);
+        // Extract the marker line — Python libraries may print warnings to stdout during import.
+        var jsonLine = command.StdOut.Split(new[] { "\r\n", "\n" }, StringSplitOptions.RemoveEmptyEntries)
+            .LastOrDefault(l => l.StartsWith("VSRGUI_PROBE:"))
+            ?? throw new InvalidOperationException($"Probe script produced no valid output:{Environment.NewLine}{command.StdOut}");
+        var jsonText = jsonLine["VSRGUI_PROBE:".Length..];
+
+        using var document = JsonDocument.Parse(jsonText);
         var root = document.RootElement;
         var hasVs = root.GetProperty("has_vapoursynth").GetBoolean();
         var hasVsrepo = root.GetProperty("has_vsrepo").GetBoolean();
@@ -194,7 +200,17 @@ public async Task<CommandResult> RunVsrepoElevatedAsync(string pythonExe, string
             };
 
             process.Start();
-            await process.WaitForExitAsync(cancellationToken);
+            try
+            {
+                await process.WaitForExitAsync(cancellationToken);
+            }
+            catch (OperationCanceledException)
+            {
+                // Best effort — Kill may fail on an elevated child from a non-elevated parent.
+                try { process.Kill(entireProcessTree: true); }
+                catch { /* ignored */ }
+                throw;
+            }
 
             var std = File.Exists(outputPath)
                 ? await File.ReadAllTextAsync(outputPath, cancellationToken)
@@ -293,6 +309,9 @@ public async Task<Dictionary<string, InstalledPackageInfo>> GetInstalledAsync(st
                 status = PackageInstallState.InstalledUnknown;
             }
 
+            // Assumed vsrepo output columns: [Name] [Installed] [Latest] [Type] [Identifier]
+            // Index from end:                  ^[^5]     [^4]       [^3]    [^2]   [^1]
+            // So tokens[^1] = Identifier, tokens[^3] = Latest (displayed as installed version reference).
             var identifier = tokens[^1].Trim();
             var installedVersion = tokens[^3].Trim();
             if (string.IsNullOrWhiteSpace(identifier))
@@ -309,8 +328,17 @@ public async Task<Dictionary<string, InstalledPackageInfo>> GetInstalledAsync(st
     public VsPackageRoot LoadDefinitions(string definitionsPath)
     {
         var json = File.ReadAllText(definitionsPath, Encoding.UTF8);
-        return JsonSerializer.Deserialize<VsPackageRoot>(json, JsonOptions)
-               ?? new VsPackageRoot();
+        var root = JsonSerializer.Deserialize<VsPackageRoot>(json, JsonOptions)
+                   ?? new VsPackageRoot();
+
+        // System.Text.Json does not enforce C# nullable annotations — explicit null in JSON overrides default.
+        root.Packages ??= [];
+        foreach (var pkg in root.Packages)
+        {
+            pkg.Releases ??= [];
+        }
+
+        return root;
     }
 
     public bool IsAdministrator()