Remove SynchronizationContext monitoring from WpfFactAttribute

Test timeouts and deadlocks are handled by other infrastructure in Roslyn. This
functionality from WpfFactAttribute was interfering.

Closes #26247

src/EditorFeatures/TestUtilities/Threading/WpfTestInvoker.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
-
-using System;
-using System.Collections.Generic;
-using System.Reflection;
-using System.Threading;
-using Xunit.Abstractions;
-using Xunit.Sdk;
-
-namespace Roslyn.Test.Utilities
-{
-    public class WpfTestInvoker : XunitTestInvoker
-    {
-        public WpfTestSharedData SharedData { get; }
-        public WpfTestInvoker(
-            WpfTestSharedData sharedData,
-            ITest test,
-            IMessageBus messageBus,
-            Type testClass,
-            object[] constructorArguments,
-            MethodInfo testMethod,
-            object[] testMethodArguments,
-            IReadOnlyList<BeforeAfterTestAttribute> beforeAfterAttributes,
-            ExceptionAggregator aggregator,
-            CancellationTokenSource cancellationTokenSource)
-        : base(test, messageBus, testClass, constructorArguments, testMethod, testMethodArguments, beforeAfterAttributes, aggregator, cancellationTokenSource)
-        {
-            SharedData = sharedData;
-        }
-
-        protected override object CallTestMethod(object testClassInstance)
-        {
-            SharedData.MonitorActiveAsyncTestSyncContext();
-            return base.CallTestMethod(testClassInstance);
-        }
-    }
-}

src/EditorFeatures/TestUtilities/Threading/WpfTestRunner.cs

@@ -71,7 +71,7 @@ protected override Task<decimal> InvokeTestMethodAsync(ExceptionAggregator aggre
                         s_wpfFactRequirementReason = null;
 
                         // Just call back into the normal xUnit dispatch process now that we are on an STA Thread with no synchronization context.
-                        var invoker = new WpfTestInvoker(SharedData, Test, MessageBus, TestClass, ConstructorArguments, TestMethod, TestMethodArguments, BeforeAfterAttributes, aggregator, CancellationTokenSource);
+                        var invoker = new XunitTestInvoker(Test, MessageBus, TestClass, ConstructorArguments, TestMethod, TestMethodArguments, BeforeAfterAttributes, aggregator, CancellationTokenSource);
                         return invoker.RunAsync().JoinUsingDispatcher(CancellationTokenSource.Token);
                     }
                     finally

src/EditorFeatures/TestUtilities/Threading/WpfTestSharedData.cs

@@ -2,15 +2,9 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using System.Threading;
-using System.Threading.Tasks;
-using System.Windows.Threading;
-using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Xunit.Abstractions;
-using Xunit.Sdk;
 
 namespace Roslyn.Test.Utilities
 {
@@ -33,13 +27,10 @@ public sealed class WpfTestSharedData
         /// </summary>
         private readonly List<string> _recentTestCases = new List<string>();
 
-        private readonly ConditionalWeakTable<AsyncTestSyncContext, object> _contextTrackingTable = new ConditionalWeakTable<AsyncTestSyncContext, object>();
-
         public Semaphore TestSerializationGate = new Semaphore(1, 1, TestSerializationGateName.ToString("N"));
 
         private WpfTestSharedData()
         {
-
         }
 
         public void ExecutingTest(ITestMethod testMethod)
@@ -59,87 +50,5 @@ public void ExecutingTest(MethodInfo testMethod)
                 _recentTestCases.Add(name);
             }
         }
-
-        /// <summary>
-        /// When a <see cref="SynchronizationContext"/> instance is used in a <see cref="WpfFactAttribute"/>
-        /// test it can cause a deadlock. This happens when there are posted actions that are not run and the test
-        /// case is non-async. 
-        /// 
-        /// The xunit framework monitors all calls to the active <see cref="SynchronizationContext"/> and it will 
-        /// wait on them to complete before finishing a test. Hence if anything is posted but not run the test will
-        /// deadlock forever waiting for this to happen.
-        /// 
-        /// This code monitors the use of our <see cref="SynchronizationContext"/> and attempts to 
-        /// detect this situation and actively fail the test when it happens. The code is a hueristic and hence 
-        /// imprecise. But is effective in finding these problmes.
-        /// </summary>
-        public void MonitorActiveAsyncTestSyncContext()
-        {
-            // To cause the test to fail we need to post an action ot the AsyncTestContext. The xunit framework 
-            // wraps such delegates in a try / catch and fails the test if any exception occurs. This is best
-            // captured at the point a posted action occurs. 
-            var asyncContext = SynchronizationContext.Current as AsyncTestSyncContext;
-            if (_contextTrackingTable.TryGetValue(asyncContext, out _))
-            {
-                return;
-            }
-
-            var dispatcher = Dispatcher.CurrentDispatcher;
-
-            void runCallbacks()
-            {
-                var fieldInfo = asyncContext.GetType().GetField("innerContext", BindingFlags.NonPublic | BindingFlags.Instance);
-                var innerContext = fieldInfo.GetValue(asyncContext) as SynchronizationContext;
-                switch (innerContext)
-                {
-                    case DispatcherSynchronizationContext _:
-                        dispatcher.DoEvents();
-                        break;
-                    default:
-                        Debug.Fail($"Unrecognized context: {asyncContext.GetType()}");
-                        break;
-                }
-            }
-
-            _contextTrackingTable.Add(asyncContext, new object());
-            var startTime = DateTime.UtcNow;
-            void checkForBad()
-            {
-                try
-                {
-                    if (!asyncContext.WaitForCompletionAsync().IsCompleted)
-                    {
-                        var span = DateTime.UtcNow - startTime;
-                        if (span > TimeSpan.FromSeconds(30) && !Debugger.IsAttached)
-                        {
-                            asyncContext?.Post(_ => throw new Exception($"Unfulfilled {nameof(SynchronizationContext)} detected"), null);
-                            runCallbacks();
-                        }
-                        else
-                        {
-                            var timer = new Task(() =>
-                            {
-                                Thread.Sleep(TimeSpan.FromSeconds(2));
-                                queueCheckForBad();
-
-                            });
-                            timer.Start(TaskScheduler.Default);
-                        }
-                    }
-                }
-                catch (Exception ex)
-                {
-                    Debug.Fail($"Exception monitoring {nameof(SynchronizationContext)}: {ex.Message}");
-                }
-            }
-
-            void queueCheckForBad()
-            {
-                var task = new Task((Action)checkForBad);
-                task.Start(new SynchronizationContextTaskScheduler(StaTaskScheduler.DefaultSta.DispatcherSynchronizationContext));
-            }
-
-            queueCheckForBad();
-        }
     }
 }