Improve diagnostics and robustness for MTP Coverlet extension

Add detailed diagnostic logging and debugger attach support via environment variables. Enhance test module path resolution and configuration logging. Refactor DI container creation and introduce MtpProcessExitHandler for in/out-of-process execution. Add default exclude filter, improve report output handling, and expand command line parsing. Integrate Microsoft.Extensions.Configuration and update test project output path for consistency.

Author: Bertk

Directory.Packages.props

@@ -27,6 +27,7 @@
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="$(MicrosoftCodeAnalysisVersion)" />
     <PackageVersion Include="Microsoft.CodeAnalysis.BannedApiAnalyzers" Version="5.0.0-1.25277.114" />
     <PackageVersion Include="Microsoft.Extensions.DependencyModel" Version="8.0.2" />
+    <PackageVersion Include="Microsoft.Extensions.Configuration" Version="10.0.1" />
     <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
     <PackageVersion Include="Microsoft.Extensions.FileSystemGlobbing" Version="8.0.0" />
     <!--For test TestInstrument_NetstandardAwareAssemblyResolver_PreserveCompilationContext-->

src/coverlet.MTP/CoverletExtensionCollector.cs

@@ -26,5 +26,6 @@ internal class CoverletExtensionConfiguration
     public bool SkipAutoProps { get; set; }
     public bool DeterministicReport { get; set; }
     public string? ExcludeAssembliesWithoutSources { get; set; }
+    public bool DisableManagedInstrumentationRestore { get; set; }
   }
 }

src/coverlet.MTP/CoverletExtensionConfiguration.cs

@@ -7,6 +7,7 @@
 using Microsoft.Testing.Platform.Extensions.TestHostControllers;
 using Microsoft.Testing.Platform.Services;
 using Microsoft.Testing.Extensions.Diagnostics;
+using Microsoft.Extensions.Configuration;
 
 namespace coverlet.Extension
 {
@@ -23,9 +24,17 @@ public static void AddCoverletExtensionProvider(this ITestApplicationBuilder bui
               serviceProvider.GetLoggerFactory()));
 
       builder.TestHostControllers.AddProcessLifetimeHandler(static serviceProvider
-          => new CoverletExtensionCollector(
-              serviceProvider.GetLoggerFactory(),
-              serviceProvider.GetCommandLineOptions()) as ITestHostProcessLifetimeHandler);
+          =>
+          {
+            if (serviceProvider.GetConfiguration() is not IConfiguration configuration)
+            {
+              throw new ArgumentNullException(nameof(configuration), "Configuration cannot be null.");
+            }
+            return new CoverletExtensionCollector(
+                serviceProvider.GetLoggerFactory(),
+                serviceProvider.GetCommandLineOptions(),
+                configuration) as ITestHostProcessLifetimeHandler;
+          });
 
       builder.CommandLine.AddProvider(() => new CoverletExtensionCommandLineProvider(_extension));
     }

src/coverlet.MTP/CoverletExtensionProvider.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Toni Solarin-Sodara
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Coverlet.Core.Abstractions;
+
+namespace coverlet.Extension.Collector
+{
+  /// <summary>
+  /// Implementation of IProcessExitHandler for Microsoft Testing Platform.
+  /// Supports both in-process and out-of-process execution modes.
+  /// </summary>
+  internal sealed class MtpProcessExitHandler : IProcessExitHandler
+  {
+    private readonly bool _isOutOfProcess;
+
+    /// <summary>
+    /// Creates a new instance of MtpProcessExitHandler.
+    /// </summary>
+    /// <param name="isOutOfProcess">
+    /// True if running in out-of-process mode (controller manages lifecycle).
+    /// False if running in-process (needs AppDomain.ProcessExit).
+    /// </param>
+    public MtpProcessExitHandler(bool isOutOfProcess = true)
+    {
+      _isOutOfProcess = isOutOfProcess;
+    }
+
+    public void Add(EventHandler handler)
+    {
+      if (_isOutOfProcess)
+      {
+        // Out-of-process: MTP handles cleanup via OnTestHostProcessExitedAsync
+        // No need to register ProcessExit handler
+        return;
+      }
+
+      // In-process: Register the handler for AppDomain.ProcessExit
+      AppDomain.CurrentDomain.ProcessExit += handler;
+    }
+  }
+}

src/coverlet.MTP/MtpProcessExitHandler.cs

@@ -54,6 +54,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Configuration" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
     <PackageReference Include="Microsoft.Testing.Platform" />
     <PackageReference Include="System.Buffers" />

src/coverlet.MTP/coverlet.MTP.csproj

@@ -33,7 +33,7 @@ public CollectCoverageTests()
   }
 
   [Fact]
-  public async Task BasicNoCoverage_CollectsDataForCoveredLines()
+  public async Task TestCodeWithoutCodeCoverage()
   {
     // Arrange
     using var testProject = CreateTestProject(includeSimpleTest: true,
@@ -303,7 +303,8 @@ private TestProject CreateTestProject(
 
     File.WriteAllText(Path.Combine(tempPath, "Tests.cs"), testCode);
 
-    return new TestProject(projectFile, Path.Combine(tempPath, "bin", _buildConfiguration, _buildTargetFramework));
+    string outputPath = Path.Combine(tempPath, "bin", _buildConfiguration.ToLower());
+    return new TestProject(projectFile, outputPath);
   }
 
   private void CreateNuGetConfig(string projectPath)