feat(plugins): wire host logger factories so plugin load stops being silent

GMConverter.CLI/Program.cs

@@ -17,7 +17,16 @@ public static int Main(string[] args)
     {
         Console.OutputEncoding = Encoding.UTF8;
 
-        PluginHost.Initialize(PluginHost.DefaultDirectory);
+        // Plugin load is observability that belongs in the same stream as the rest of the CLI's
+        // output. A console logger at Information level surfaces plugin discovery + load failures
+        // alongside conversion progress, so a user running the CLI sees plugin issues immediately
+        // instead of hunting for them.
+        using var pluginLoggerFactory = LoggerFactory.Create(builder =>
+        {
+            builder.SetMinimumLevel(LogLevel.Information);
+            builder.AddConsole();
+        });
+        PluginHost.Initialize(PluginHost.DefaultDirectory, pluginLoggerFactory);
 
         var rootCommand = CreateRootCommand();
 

GMConverter.UI/Program.cs

@@ -1,5 +1,7 @@
 using Avalonia;
 using GMConverter.Plugins;
+using GMConverter.UI.Services;
+using Microsoft.Extensions.Logging;
 
 namespace GMConverter.UI;
 
@@ -19,7 +21,18 @@ public static void Main(string[] args)
             licenseType: "OpenSourceLicense",
             license: "A543-105E-0047-F209-CC6E-32CD-D155-4F0F-11AD-2706-9E68-7A5B-4945-D56B-9F96-C0CB-A45F-9339-DB9E-F4CE-C84A-DFAD-82B5-B095-1B");
 
-        PluginHost.Initialize(PluginHost.DefaultDirectory);
+        // Plugin load happens before Avalonia is initialized, so we cannot route plugin diagnostics
+        // through UiLogSink (which posts to Dispatcher.UIThread). A simple file-backed logger
+        // captures plugin discovery + load failures into %TEMP%\GMConverter.Plugins.log so the
+        // user has a place to look when a plugin fails to register importers/exporters/explorers
+        // at startup. Piping plugin events into the in-app console once Avalonia is ready is a
+        // follow-up.
+        using var pluginLoggerFactory = LoggerFactory.Create(builder =>
+        {
+            builder.SetMinimumLevel(LogLevel.Information);
+            builder.AddProvider(new PluginLogFileProvider());
+        });
+        PluginHost.Initialize(PluginHost.DefaultDirectory, pluginLoggerFactory);
 
         BuildAvaloniaApp().StartWithClassicDesktopLifetime(args);
     }

GMConverter.UI/Services/PluginLogFileProvider.cs

@@ -0,0 +1,97 @@
+using System.Globalization;
+using Microsoft.Extensions.Logging;
+
+namespace GMConverter.UI.Services;
+
+/// <summary>
+/// Minimal file-backed <see cref="ILoggerProvider"/> used during host startup before Avalonia
+/// is ready (and therefore before <see cref="UiLogSink"/> can post entries to the UI thread).
+/// Plugin discovery and load failures land here so they aren't silent if a plugin fails to load
+/// at startup. The log path is exposed as a static property so the rest of the app can surface
+/// it (e.g. in an "About" pane) when we eventually wire that up.
+/// </summary>
+internal sealed class PluginLogFileProvider : ILoggerProvider
+{
+    public static string LogPath { get; } =
+        Path.Join(Path.GetTempPath(), "GMConverter.Plugins.log");
+
+    private static readonly object _writeLock = new();
+
+    static PluginLogFileProvider()
+    {
+        try
+        {
+            File.WriteAllText(
+                LogPath,
+                FormattableString.Invariant(
+                    $"# GMConverter plugin log | pid {Environment.ProcessId} | started {DateTimeOffset.Now:O}{Environment.NewLine}"));
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException or System.Security.SecurityException)
+        {
+            // Telemetry is best-effort; never propagate filesystem failures from instrumentation.
+            _ = ex;
+        }
+    }
+
+    public ILogger CreateLogger(string categoryName)
+    {
+        return new FileLogger(categoryName);
+    }
+
+    public void Dispose()
+    {
+    }
+
+    private sealed class FileLogger(string categoryName) : ILogger
+    {
+        public IDisposable? BeginScope<TState>(TState state)
+            where TState : notnull
+        {
+            return null;
+        }
+
+        public bool IsEnabled(LogLevel logLevel)
+        {
+            return logLevel >= LogLevel.Information;
+        }
+
+        public void Log<TState>(
+            LogLevel logLevel,
+            EventId eventId,
+            TState state,
+            Exception? exception,
+            Func<TState, Exception?, string> formatter)
+        {
+            if (!IsEnabled(logLevel))
+            {
+                return;
+            }
+
+            var message = formatter(state, exception);
+            var line = string.Format(
+                CultureInfo.InvariantCulture,
+                "[{0:O}] [{1,-11}] {2}: {3}",
+                DateTimeOffset.Now,
+                logLevel,
+                categoryName,
+                message);
+
+            lock (_writeLock)
+            {
+                try
+                {
+                    File.AppendAllText(LogPath, line + Environment.NewLine);
+                    if (exception is not null)
+                    {
+                        File.AppendAllText(LogPath, exception.ToString() + Environment.NewLine);
+                    }
+                }
+                catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+                {
+                    // Best-effort telemetry — filesystem failures here must never block plugin load.
+                    _ = ex;
+                }
+            }
+        }
+    }
+}