Avoid logging >Task returned false but did not log an error.< (#2557)

* Avoid logging >Task returned false but did not log an error.< on test failure

* Add VSTEST_BUILD_DEBUG env var

* Using namespaces

Author: nohwnd

src/Microsoft.TestPlatform.Build/Tasks/VSTestTask.cs

@@ -5,7 +5,9 @@ namespace Microsoft.TestPlatform.Build.Tasks
 {
     using System;
     using System.Collections.Generic;
+    using System.Diagnostics;
     using System.Linq;
+    using System.Threading;
     using Microsoft.Build.Framework;
     using Microsoft.Build.Utilities;
     using Microsoft.TestPlatform.Build.Resources;
@@ -161,6 +163,27 @@ public override bool Execute()
             var traceEnabledValue = Environment.GetEnvironmentVariable("VSTEST_BUILD_TRACE");
             Tracing.traceEnabled = !string.IsNullOrEmpty(traceEnabledValue) && traceEnabledValue.Equals("1", StringComparison.OrdinalIgnoreCase);
 
+            var debugEnabled = Environment.GetEnvironmentVariable("VSTEST_BUILD_DEBUG");
+            if (!string.IsNullOrEmpty(debugEnabled) && debugEnabled.Equals("1", StringComparison.Ordinal))
+            {
+                Console.WriteLine("Waiting for debugger attach...");
+
+                var currentProcess = Process.GetCurrentProcess();
+                Console.WriteLine(string.Format("Process Id: {0}, Name: {1}", currentProcess.Id, currentProcess.ProcessName));
+
+                while (!Debugger.IsAttached)
+                {
+                    Thread.Sleep(1000);
+                }
+
+                Debugger.Break();
+            }
+
+            // Avoid logging "Task returned false but did not log an error." on test failure, because we don't
+            // write MSBuild error. https://github.com/dotnet/msbuild/blob/51a1071f8871e0c93afbaf1b2ac2c9e59c7b6491/src/Framework/IBuildEngine7.cs#L12
+            var allowfailureWithoutError = BuildEngine.GetType().GetProperty("AllowFailureWithoutError");
+            allowfailureWithoutError?.SetValue(BuildEngine, true);
+
             vsTestForwardingApp = new VSTestForwardingApp(this.VSTestConsolePath, this.CreateArgument());
             if (!string.IsNullOrEmpty(this.VSTestFramework))
             {