Optimize the server mode discovery workflow

samples/Playground/Playground.csproj

@@ -11,14 +11,8 @@
   <ItemGroup>
     <ProjectReference Include="$(RepoRoot)src\Platform\Microsoft.Testing.Platform\Microsoft.Testing.Platform.csproj" />
     <ProjectReference Include="$(RepoRoot)src\Adapter\MSTest.TestAdapter\MSTest.TestAdapter.csproj" />
-    <ProjectReference Include="$(RepoRoot)src\Analyzers\MSTest.Analyzers.CodeFixes\MSTest.Analyzers.CodeFixes.csproj"
-                      PrivateAssets="all"
-                      ReferenceOutputAssembly="false"
-                      OutputItemType="Analyzer" />
-    <ProjectReference Include="$(RepoRoot)src\Analyzers\MSTest.Analyzers\MSTest.Analyzers.csproj"
-                      PrivateAssets="all"
-                      ReferenceOutputAssembly="false"
-                      OutputItemType="Analyzer" />
+    <ProjectReference Include="$(RepoRoot)src\Analyzers\MSTest.Analyzers.CodeFixes\MSTest.Analyzers.CodeFixes.csproj" PrivateAssets="all" ReferenceOutputAssembly="false" OutputItemType="Analyzer" />
+    <ProjectReference Include="$(RepoRoot)src\Analyzers\MSTest.Analyzers\MSTest.Analyzers.csproj" PrivateAssets="all" ReferenceOutputAssembly="false" OutputItemType="Analyzer" />
     <PackageReference Include="StreamJsonRpc" />
     <ProjectReference Include="$(RepoRoot)src\Platform\Microsoft.Testing.Extensions.Telemetry\Microsoft.Testing.Extensions.Telemetry.csproj" />
   </ItemGroup>
@@ -39,4 +33,6 @@
     <ProjectCapability Include="TestContainer" />
   </ItemGroup>
 
+  <!-- Import the capabilities for the Microsoft.Testing.Platform -->
+  <Import Project="$(RepoRoot)src\Platform\Microsoft.Testing.Platform\buildMultiTargeting\Microsoft.Testing.Platform.props"/>
 </Project>

samples/Playground/Program.cs

@@ -8,6 +8,7 @@
 using Microsoft.Testing.Platform.Extensions.TestHostControllers;
 using Microsoft.Testing.Platform.Messages;
 using Microsoft.Testing.Platform.ServerMode.IntegrationTests.Messages.V100;
+using Microsoft.Testing.Platform.Services;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 using MSTest.Acceptance.IntegrationTests.Messages.V100;
@@ -24,12 +25,12 @@ public static async Task<int> Main(string[] args)
         if (Environment.GetEnvironmentVariable("TESTSERVERMODE") != "1")
         {
             // To attach to the children
-            // Microsoft.Testing.TestInfrastructure.DebuggerUtility.AttachCurrentProcessToParentVSProcess();
+            Microsoft.Testing.TestInfrastructure.DebuggerUtility.AttachCurrentProcessToParentVSProcess();
             ITestApplicationBuilder testApplicationBuilder = await TestApplication.CreateBuilderAsync(args);
             testApplicationBuilder.AddMSTest(() => [Assembly.GetEntryAssembly()!]);
 
             // Custom test host controller extension
-            // testApplicationBuilder.TestHostControllers.AddProcessLifetimeHandler(s => new OutOfProc(s.GetMessageBus()));
+            testApplicationBuilder.TestHostControllers.AddProcessLifetimeHandler(s => new OutOfProc(s.GetMessageBus()));
 
             // Enable Trx
             // testApplicationBuilder.AddTrxReportProvider();

src/Platform/Microsoft.Testing.Platform/Hosts/ConsoleTestHost.cs

@@ -66,7 +66,8 @@ protected override async Task<int> InternalRunAsync()
             _testFrameworkManager,
             _testHostManager,
             new MessageBusProxy(),
-            ServiceProvider.GetCommandLineOptions().IsOptionSet(PlatformCommandLineProvider.DiscoverTestsOptionKey)));
+            ServiceProvider.GetCommandLineOptions().IsOptionSet(PlatformCommandLineProvider.DiscoverTestsOptionKey),
+            false));
 
         ITelemetryCollector telemetry = ServiceProvider.GetTelemetryCollector();
         ITelemetryInformation telemetryInformation = ServiceProvider.GetTelemetryInformation();

src/Platform/Microsoft.Testing.Platform/Hosts/ServerTestHost.cs

@@ -461,7 +461,8 @@ private async Task<ResponseArgsBase> ExecuteRequestAsync(RequestArgsBase args, s
             _testFrameworkManager,
             _testSessionManager,
             new MessageBusProxy(),
-            method == JsonRpcMethods.TestingDiscoverTests));
+            method == JsonRpcMethods.TestingDiscoverTests,
+            true));
 
         DateTimeOffset adapterLoadStop = _clock.UtcNow;
 

src/Platform/Microsoft.Testing.Platform/Hosts/TestFrameworkBuilderData.cs

@@ -15,7 +15,8 @@ internal class TestFrameworkBuilderData(ServiceProvider serviceProvider, ITestEx
     ITestFrameworkInvoker testExecutionRequestInvoker, ITestExecutionFilterFactory testExecutionFilterFactory,
     IPlatformOutputDevice platformOutputDisplayService, IEnumerable<IDataConsumer> serverPerCallConsumers,
     TestFrameworkManager testFrameworkManager, TestHostManager testSessionManager, MessageBusProxy messageBusProxy,
-    bool isForDiscoveryRequest)
+    bool isForDiscoveryRequest,
+    bool isJsonRpcProtocol)
 {
     public ServiceProvider ServiceProvider { get; } = serviceProvider;
 
@@ -36,4 +37,6 @@ internal class TestFrameworkBuilderData(ServiceProvider serviceProvider, ITestEx
     public MessageBusProxy MessageBusProxy { get; } = messageBusProxy;
 
     public bool IsForDiscoveryRequest { get; } = isForDiscoveryRequest;
+
+    public bool IsJsonRpcProtocol { get; } = isJsonRpcProtocol;
 }

src/Platform/Microsoft.Testing.Platform/Hosts/TestHostBuilder.cs

@@ -740,10 +740,12 @@ private async Task<ITestFramework> BuildTestFrameworkAsync(TestFrameworkBuilderD
 
         IDataConsumer[] dataConsumerServices = dataConsumersBuilder.ToArray();
 
-        // Build the message hub
+        // Build the message bus
         // If we're running discovery command line we don't want to process any messages coming from the adapter so we filter out all extensions
         // adding a custom message bus that will simply forward to the output display for better performance
-        if (serviceProvider.GetCommandLineOptions().IsOptionSet(PlatformCommandLineProvider.DiscoverTestsOptionKey))
+        if (serviceProvider.GetCommandLineOptions().IsOptionSet(PlatformCommandLineProvider.DiscoverTestsOptionKey)
+            // In case of server mode the discovery is handled by the ServerHost using the standard message bus
+            && !testFrameworkBuilderData.IsJsonRpcProtocol)
         {
             ListTestsMessageBus concreteMessageBusService = new(
                 serviceProvider.GetTestFramework(),

src/Platform/Microsoft.Testing.Platform/buildMultiTargeting/Microsoft.Testing.Platform.props

@@ -1,8 +1,12 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <Project>
   <ItemGroup>
-    <TestingPlatformMetadata Include="ExitOnProcessExitCapability" >
+    <!-- For VS Test Explorer -->
+    <ProjectCapability Include="TestingPlatformServer.ExitOnProcessExitCapability">
       <Description>--exit-on-process-exit: Close the test process if specific process exits. Process PID must be provided.</Description>
-    </TestingPlatformMetadata>
+    </ProjectCapability>
+    <ProjectCapability Include="TestingPlatformServer.UseListTestsOptionForDiscoveryCapability">
+      <Description>The implementation handle the --list-tests in --server [jsonrpc] during discovery</Description>
+    </ProjectCapability>
   </ItemGroup>
 </Project>