chore: Change compile constants confition to improve usability + rely…

… on running platform to check is 2nd app is surppoted instead of compile const

src/Directory.Build.props

@@ -36,9 +36,6 @@
 		<AnalysisLevel>latest</AnalysisLevel>
 		<AnalysisModePerformance>AllEnabledByDefault</AnalysisModePerformance>
 	</PropertyGroup>
-	<ItemGroup>
-		<PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="7.0.0-preview1.22403.2" PrivateAssets="All" />
-	</ItemGroup>
 
 	<Choose>
 		<When Condition="'$(IsTestProject)' != 'true' and '$(SourceLinkEnabled)' != 'false' and '$(IsSampleProject)' != 'true'">

src/Uno.UI.RuntimeTests.Engine.Library/Engine/ExternalRunner/_Private/DevServer.cs

@@ -1,10 +1,11 @@
-#if !UNO_RUNTIMETESTS_DISABLE_UI && (__SKIA__ || IS_SECONDARY_APP_SUPPORTED)
+#if !UNO_RUNTIMETESTS_DISABLE_UI && HAS_UNO_WINUI // HAS_UNO_WINUI: exclude non net7 platforms
 #nullable enable
 
 #if !IS_UNO_RUNTIMETEST_PROJECT
 #pragma warning disable
 #endif
 #pragma warning disable CA1848 // Log perf
+#pragma warning disable CS1998 // No await
 namespace Uno.UI.RuntimeTests.Internal.Helpers;
 
 /// <summary>
@@ -14,6 +15,9 @@ namespace Uno.UI.RuntimeTests.Internal.Helpers;
 /// This class is intended to be used only by the the test engine itself and should not be used by applications.
 /// API contract is not guaranteed and might change in future releases.
 /// </remarks>
+[global::System.Runtime.Versioning.SupportedOSPlatform("windows")]
+[global::System.Runtime.Versioning.SupportedOSPlatform("linux")]
+[global::System.Runtime.Versioning.SupportedOSPlatform("freeBSD")]
 internal sealed partial class DevServer : global::System.IAsyncDisposable
 {
 	private static readonly global::Microsoft.Extensions.Logging.ILogger _log = global::Uno.Extensions.LogExtensionPoint.Log(typeof(DevServer));
@@ -28,7 +32,7 @@ internal sealed partial class DevServer : global::System.IAsyncDisposable
 	public static async global::System.Threading.Tasks.Task<DevServer> Start(global::System.Threading.CancellationToken ct)
 	{
 #if !HAS_UNO_DEVSERVER
-		throw new NotSupportedException("Dev server has not been referenced.");
+		throw new global::System.NotSupportedException("Dev server has not been referenced.");
 #else
 		var path = await GetDevServer(ct);
 		var port = GetTcpPort();

src/Uno.UI.RuntimeTests.Engine.Library/Engine/ExternalRunner/_Private/ProcessHelper.cs

@@ -1,4 +1,4 @@
-#if !UNO_RUNTIMETESTS_DISABLE_UI && (__SKIA__ || IS_SECONDARY_APP_SUPPORTED)
+#if !UNO_RUNTIMETESTS_DISABLE_UI && HAS_UNO_WINUI // HAS_UNO_WINUI: exclude non net7 platforms
 #nullable enable
 
 #if !IS_UNO_RUNTIMETEST_PROJECT
@@ -24,6 +24,9 @@ namespace Uno.UI.RuntimeTests.Internal.Helpers;
 /// This class is intended to be used only by the the test engine itself and should not be used by applications.
 /// API contract is not guaranteed and might change in future releases.
 /// </remarks>
+[global::System.Runtime.Versioning.SupportedOSPlatform("windows")]
+[global::System.Runtime.Versioning.SupportedOSPlatform("linux")]
+[global::System.Runtime.Versioning.SupportedOSPlatform("freeBSD")]
 internal static partial class ProcessHelper
 {
 	public static async Task<string> ExecuteAsync(

src/Uno.UI.RuntimeTests.Engine.Library/Engine/ExternalRunner/_Private/SecondaryApp.cs

@@ -1,14 +1,12 @@
-#if !UNO_RUNTIMETESTS_DISABLE_UI
+using System;
+
+#if !UNO_RUNTIMETESTS_DISABLE_UI
 #nullable enable
 
 #if !IS_UNO_RUNTIMETEST_PROJECT
 #pragma warning disable
 #endif
 
-#if __SKIA__
-#define IS_SECONDARY_APP_SUPPORTED
-#endif
-
 namespace Uno.UI.RuntimeTests.Internal.Helpers;
 
 /// <summary>
@@ -23,9 +21,9 @@ internal static partial class SecondaryApp
 	/// <summary>
 	/// Gets a boolean indicating if the current platform supports running tests in a secondary app.
 	/// </summary>
-	public static bool IsSupported => // Note: not as const to avoid "CS0162 unreachable code" warning
-#if IS_SECONDARY_APP_SUPPORTED
-		true;
+	public static bool IsSupported =>
+#if HAS_UNO_WINUI // HAS_UNO_WINUI: exclude non net7 platforms
+		global::System.OperatingSystem.IsWindows() || global::System.OperatingSystem.IsLinux() || global::System.OperatingSystem.IsFreeBSD();
 #else
 		false;
 #endif
@@ -39,9 +37,17 @@ internal static partial class SecondaryApp
 	/// <returns>The test results.</returns>
 	internal static async global::System.Threading.Tasks.Task<TestCaseResult[]> RunTest(UnitTestEngineConfig config, global::System.Threading.CancellationToken ct, bool isAppVisible = false)
 	{
-#if !IS_SECONDARY_APP_SUPPORTED
-		throw new global::System.NotSupportedException("Secondary app is not supported on this platform.");
+		if (!IsSupported)
+		{
+			throw new global::System.NotSupportedException("Secondary app is not supported on this platform.");
+		}
+
+#if !HAS_UNO_WINUI // HAS_UNO_WINUI: exclude non net7 platforms
+#pragma warning disable CA1825 // Array.Empty not available on UWP
+		return new TestCaseResult[0]; // Non reachable code.
+#pragma warning restore CA1825
 #else
+#pragma warning disable CA1416 // Validate platform compatibility => This is checked by the IsSupported property.
 		// First we fetch and start the dev-server (needed to HR tests for instance)
 		await using var devServer = await DevServer.Start(ct);
 
@@ -98,6 +104,7 @@ internal static partial class SecondaryApp
 		await childProcess.ExecuteAndLogAsync(typeof(SecondaryApp).CreateScopedLog($"CHILD_TEST_APP_{(global::System.Threading.Interlocked.Increment(ref _instance)):D2}"), ct);
 
 		return testOutput;
+#pragma warning restore CA1416 // Validate platform compatibility
 #endif
 	}
 }