[release/11.0.1xx-preview7] Harden MTP artifact post-processing and add an opt-out

src/Cli/Microsoft.DotNet.Cli.Definitions/CommandDefinitionStrings.resx

@@ -494,6 +494,9 @@ This is equivalent to deleting project.assets.json.</value>
   <data name="CmdNoHttpCacheOptionDescription" xml:space="preserve">
     <value>Disable Http Caching for packages.</value>
   </data>
+  <data name="CmdNoArtifactPostProcessingDescription" xml:space="preserve">
+    <value>Do not merge compatible artifacts, such as TRX reports or code coverage files, produced by different test applications.</value>
+  </data>
   <data name="CmdNoProgressDescription" xml:space="preserve">
     <value>Disable progress reporting.</value>
   </data>

src/Cli/Microsoft.DotNet.Cli.Definitions/Commands/Test/TestCommandDefinition.MicrosoftTestingPlatform.cs

@@ -133,6 +133,12 @@ public sealed partial class MicrosoftTestingPlatform : TestCommandDefinition, IC
             Arity = ArgumentArity.Zero
         };
 
+        public readonly Option<bool> NoArtifactPostProcessingOption = new("--no-artifact-post-processing")
+        {
+            Description = CommandDefinitionStrings.CmdNoArtifactPostProcessingDescription,
+            Arity = ArgumentArity.Zero
+        };
+
         public readonly Option<OutputOptions> OutputOption = new("--output")
         {
             Description = CommandDefinitionStrings.CmdTestOutputDescription,
@@ -215,6 +221,7 @@ public MicrosoftTestingPlatform()
             Options.Add(UseCurrentRuntimeOption);
             Options.Add(NoAnsiOption);
             Options.Add(NoProgressOption);
+            Options.Add(NoArtifactPostProcessingOption);
             Options.Add(OutputOption);
             Options.Add(ListTestsOption);
             Options.Add(NoLaunchProfileOption);

src/Cli/dotnet/Commands/Test/MTP/ArtifactPostProcessingManager.cs

@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.ComponentModel;
 using System.Globalization;
 using System.Text.Json;
 using Microsoft.DotNet.Cli.Commands.Test.IPC.Models;
@@ -112,29 +111,29 @@ public async Task ExecuteAsync(
 
                 if (invocation.FailureMessage is { } failureMessage)
                 {
-                    output.WriteWarningMessage(string.Format(
+                    ReportFailureUnlessCancelled(output, ctrlC, string.Format(
                         CultureInfo.CurrentCulture,
                         CliCommandStrings.ArtifactPostProcessingFailed,
                         job.Application.Module.TargetPath,
                         failureMessage));
                 }
                 else if (exitCode != ExitCode.Success)
                 {
-                    output.WriteWarningMessage(string.Format(
+                    ReportFailureUnlessCancelled(output, ctrlC, string.Format(
                         CultureInfo.CurrentCulture,
                         CliCommandStrings.ArtifactPostProcessingProcessFailed,
                         job.Application.Module.TargetPath,
                         exitCode));
                 }
             }
-            catch (Exception ex) when (ex is IOException
-                or UnauthorizedAccessException
-                or InvalidOperationException
-                or Win32Exception
-                or NotSupportedException
-                or TimeoutException)
+            catch (Exception ex)
             {
-                output.WriteWarningMessage(string.Format(
+                // Post-processing is a best-effort convenience on top of a completed test run: the
+                // original artifacts are always still on disk and still reported, so no failure here
+                // may escape and turn a finished run into a CLI crash with a different exit code.
+                Logger.LogTrace($"Artifact post-processing with '{job.Application.Module.TargetPath}' failed: {ex}");
+
+                ReportFailureUnlessCancelled(output, ctrlC, string.Format(
                     CultureInfo.CurrentCulture,
                     CliCommandStrings.ArtifactPostProcessingFailed,
                     job.Application.Module.TargetPath,
@@ -157,6 +156,24 @@ or NotSupportedException
         }
     }
 
+    /// <summary>
+    /// Reports a post-processing failure, unless the user cancelled the run. Cancellation kills the
+    /// post-processing process the same way it kills a test application, so the resulting failure is
+    /// the cancellation the user asked for rather than a post-processing problem worth reporting.
+    /// </summary>
+    internal static void ReportFailureUnlessCancelled(
+        TerminalTestReporter output,
+        CtrlCCancellationManager ctrlC,
+        string message)
+    {
+        if (ctrlC.Token.IsCancellationRequested)
+        {
+            return;
+        }
+
+        output.WriteWarningMessage(message);
+    }
+
     internal IReadOnlyList<ArtifactPostProcessingApplication> SnapshotApplications()
     {
         lock (_lock)

src/Cli/dotnet/Commands/Test/MTP/MicrosoftTestingPlatformTestCommand.cs

@@ -116,7 +116,10 @@ public int Run(ParseResult parseResult, bool isHelp)
                 exitCode = ExitCode.TestSessionAborted;
             }
 
-            if (!testOptions.IsHelp && !testOptions.IsDiscovery && !ctrlC.Token.IsCancellationRequested)
+            if (!testOptions.IsHelp
+                && !testOptions.IsDiscovery
+                && !parseResult.GetValue(definition.NoArtifactPostProcessingOption)
+                && !ctrlC.Token.IsCancellationRequested)
             {
                 artifactPostProcessingManager.ExecuteAsync(buildOptions, output, ctrlC).GetAwaiter().GetResult();
             }