Minor optimizations

TestPlatform.sln

@@ -189,8 +189,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "testhost.arm64", "src\testh
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DumpMinitool.arm64", "src\DataCollectors\DumpMinitool.arm64\DumpMinitool.arm64.csproj", "{62E9D32B-B989-43CF-81A2-B38B3367FCA3}"
 EndProject
-Project("{D954291E-2A0B-460D-934E-DC6B0785DB48}") = "Microsoft.TestPlatform.Nullability", "src\Microsoft.TestPlatform.Nullability\Microsoft.TestPlatform.Nullability.shproj", "{9DF3BC3C-2A53-46E7-9291-40728ACE5F82}"
-EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -1025,7 +1023,6 @@ Global
 		{29270853-90DC-4C39-9621-F47AE40A79B6} = {B27FAFDF-2DBA-4AB0-BA85-FD5F21D359D6}
 		{186069FE-E1E8-4DE1-BEA4-0FF1484D22D1} = {ED0C35EB-7F31-4841-A24F-8EB708FFA959}
 		{62E9D32B-B989-43CF-81A2-B38B3367FCA3} = {B705537C-B82C-4A30-AFA5-6244D9A7DAEB}
-		{9DF3BC3C-2A53-46E7-9291-40728ACE5F82} = {7D4082EA-7AC9-4DFB-98E8-C5E08BDC0EC3}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {0541B30C-FF51-4E28-B172-83F5F3934BCD}
@@ -1039,7 +1036,6 @@ Global
 		src\Microsoft.TestPlatform.Nullability\Microsoft.TestPlatform.Nullability.projitems*{68adc720-316e-4895-9f8e-c3ccadd262be}*SharedItemsImports = 5
 		src\Microsoft.TestPlatform.Execution.Shared\Microsoft.TestPlatform.Execution.Shared.projitems*{71cb42ff-e750-4a3b-9c3a-ac938853cc89}*SharedItemsImports = 5
 		src\Microsoft.TestPlatform.Execution.Shared\Microsoft.TestPlatform.Execution.Shared.projitems*{7f26eda3-c8c4-4b7f-a9b6-d278c2f40a13}*SharedItemsImports = 13
-		src\Microsoft.TestPlatform.Nullability\Microsoft.TestPlatform.Nullability.projitems*{9df3bc3c-2a53-46e7-9291-40728ace5f82}*SharedItemsImports = 13
 		src\Microsoft.TestPlatform.Nullability\Microsoft.TestPlatform.Nullability.projitems*{fbf74c8f-695c-4967-84ac-358eefb1376d}*SharedItemsImports = 5
 	EndGlobalSection
 EndGlobal

src/Microsoft.TestPlatform.Common/Logging/InternalTestLoggerEvents.cs

@@ -316,9 +316,25 @@ private void TestRunMessageHandler(object sender, TestRunMessageEventArgs e)
     /// </summary>
     private void SafeInvokeAsync(Func<MulticastDelegate> eventHandlersFactory, EventArgs args, int size, string traceDisplayName)
     {
+        // If you are wondering why this is taking a Func<MulticastDelegate> rather than just a MulticastDelegate it is because
+        // taking just that will capture only the subscribers that were present at the time we passed the delegate into this
+        // method. Which means that if there were no subscribers we will capture null, and later when the queue is unpaused
+        // we won't call any logger that subscribed while the queue was paused.
+
         ValidateArg.NotNull(eventHandlersFactory, nameof(eventHandlersFactory));
         ValidateArg.NotNull(args, nameof(args));
 
+        // When the logger event queue is paused we want to enqueue the work because maybe there are no
+        // loggers yet, and there are maybe errors that the loggers should report once they subscribe.
+        // When the queue is running, don't bother adding tasks to the queue when there are no subscribers
+        // because there is very slim chance that a new logger will be added in the few milliseconds that will
+        // pass until we process the task, and it just puts pressure on the queue. If this proves to be a problem
+        // we have a race condition, and that side should pause the queue while it adds all the loggers and then resume.
+        if (!_loggerEventQueue.IsPaused && eventHandlersFactory() == null)
+        {
+            return;
+        }
+
         // Invoke the handlers on a background thread.
         _loggerEventQueue.QueueJob(
             () =>

src/Microsoft.TestPlatform.CommunicationUtilities/JsonDataSerializer.cs

@@ -50,6 +50,7 @@ private JsonDataSerializer()
         s_payloadSerializer = JsonSerializer.Create(jsonSettings);
         s_payloadSerializer2 = JsonSerializer.Create(jsonSettings);
 
+        var contractResolver = new DefaultTestPlatformContractResolver();
         s_fastJsonSettings = new JsonSerializerSettings
         {
             DateFormatHandling = jsonSettings.DateFormatHandling,
@@ -61,11 +62,11 @@ private JsonDataSerializer()
             // of changing how our consumers get their data.
             // NullValueHandling = NullValueHandling.Ignore,
 
-            ContractResolver = new DefaultTestPlatformContractResolver(),
+            ContractResolver = contractResolver,
         };
 
         s_payloadSerializer.ContractResolver = new TestPlatformContractResolver1();
-        s_payloadSerializer2.ContractResolver = new DefaultTestPlatformContractResolver();
+        s_payloadSerializer2.ContractResolver = contractResolver;
 
 #if TRACE_JSON_SERIALIZATION
         // MemoryTraceWriter can help diagnose serialization issues. Enable it for

src/Microsoft.TestPlatform.CoreUtilities/Utilities/JobQueue.cs

@@ -84,6 +84,8 @@ public class JobQueue<T> : IDisposable
     /// </summary>
     private readonly Action<string> _exceptionLogger;
 
+    public bool IsPaused { get; private set; }
+
     /// <summary>
     /// Initializes a new instance of the <see cref="JobQueue{T}"/> class.
     /// </summary>
@@ -128,7 +130,7 @@ public JobQueue(Action<T> processJob, string displayName, int maxQueueLength, in
         _exceptionLogger = exceptionLogger;
 
         // Setup the background thread to process the jobs.
-        _backgroundJobProcessor = new Task(() => BackgroundJobProcessor(), TaskCreationOptions.LongRunning);
+        _backgroundJobProcessor = new Task(() => BackgroundJobProcessor(_displayName), TaskCreationOptions.LongRunning);
         _backgroundJobProcessor.Start();
     }
 
@@ -155,6 +157,7 @@ public void Pause()
         CheckDisposed();
 
         // Do not allow any jobs to be processed.
+        IsPaused = true;
         _queueProcessing.Reset();
     }
 
@@ -167,6 +170,7 @@ public void Resume()
 
         // Resume processing of jobs.
         _queueProcessing.Set();
+        IsPaused = false;
     }
 
     /// <summary>
@@ -275,8 +279,11 @@ private void CheckDisposed()
     /// <summary>
     /// Method which processes the jobs on the background thread.
     /// </summary>
-    private void BackgroundJobProcessor()
+    private void BackgroundJobProcessor(string threadName)
     {
+#if DEBUG && (NETFRAMEWORK || NET || NETSTANDARD2_0_OR_GREATER)
+        Thread.CurrentThread.Name = threadName;
+#endif
         bool shutdown = false;
 
         do

src/Microsoft.TestPlatform.CoreUtilities/Utilities/MulticastDelegateUtilities.cs

@@ -59,17 +59,22 @@ public static void SafeInvoke(this Delegate delegates, object sender, object arg
                 try
                 {
                     handler.DynamicInvoke(sender, args);
-                    EqtTrace.Verbose("MulticastDelegateUtilities.SafeInvoke: {0}: Invoking callback {1}/{2} for {3}.{4}, took {5} ms.",
-                            traceDisplayName,
-                            ++i,
-                            invocationList.Length,
-                            handler.GetTargetName(),
-                            handler.GetMethodName(),
-                            stopwatch.ElapsedMilliseconds);
+                    if (EqtTrace.IsVerboseEnabled)
+                    {
+                        EqtTrace.Verbose("MulticastDelegateUtilities.SafeInvoke: {0}: Invoking callback {1}/{2} for {3}.{4}, took {5} ms.",
+                                traceDisplayName,
+                                ++i,
+                                invocationList.Length,
+                                handler.GetTargetName(),
+                                handler.GetMethodName(),
+                                stopwatch.ElapsedMilliseconds);
+                    }
                 }
                 catch (TargetInvocationException exception)
                 {
-                    EqtTrace.Error(
+                    if (EqtTrace.IsErrorEnabled)
+                    {
+                        EqtTrace.Error(
                         "MulticastDelegateUtilities.SafeInvoke: {0}: Invoking callback {1}/{2} for {3}.{4}, failed after {5} ms with: {6}.",
                         ++i,
                         invocationList.Length,
@@ -78,6 +83,7 @@ public static void SafeInvoke(this Delegate delegates, object sender, object arg
                         traceDisplayName,
                         stopwatch.ElapsedMilliseconds,
                         exception);
+                    }
                 }
             }
         }

src/Microsoft.TestPlatform.CrossPlatEngine/Discovery/DiscoveryManager.cs

@@ -123,11 +123,9 @@ public void DiscoverTests(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEve
             // If there are sources to discover
             if (verifiedExtensionSourceMap.Any())
             {
-                new DiscovererEnumerator(_requestData, discoveryResultCache, _cancellationTokenSource.Token).LoadTests(
-                    verifiedExtensionSourceMap,
-                    RunSettingsUtilities.CreateAndInitializeRunSettings(discoveryCriteria.RunSettings),
-                    discoveryCriteria.TestCaseFilter,
-                    _sessionMessageLogger);
+                var runSettings = RunSettingsUtilities.CreateAndInitializeRunSettings(discoveryCriteria.RunSettings);
+                var discovererEnumerator = new DiscovererEnumerator(_requestData, discoveryResultCache, _cancellationTokenSource.Token);
+                discovererEnumerator.LoadTests(verifiedExtensionSourceMap, runSettings, discoveryCriteria.TestCaseFilter, _sessionMessageLogger);
             }
         }
         finally