fix: HostBuilder.Build() shares LogExtensionPoint.AmbientLoggerFactory

src/Uno.Extensions.Hosting.UI.Tests/HostBuilderTests.cs

@@ -0,0 +1,34 @@
+using System;
+using System.IO;
+using System.Text.Json;
+using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Uno.Extensions.Hosting.Tests;
+
+[TestClass]
+public class HostBuilderTests
+{
+	[TestMethod]
+	public void After_Build_ILoggerFactory_Is_AmbientLogger()
+	{
+		var originalAmbientLoggerFactory = Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory;
+		try
+		{
+			var myLoggerFactory = new LoggerFactory();
+			Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory = myLoggerFactory;
+			var hostBuilder = new HostBuilder();
+			var host = hostBuilder.Build();
+			var serviceLoggerFactory = host.Services.GetService<ILoggerFactory>();
+			serviceLoggerFactory.Should().NotBeNull();
+			serviceLoggerFactory.Should().Be(myLoggerFactory);
+		}
+		finally
+		{
+			Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory = originalAmbientLoggerFactory;
+		}
+	}
+}

src/Uno.Extensions.Hosting.UI.Tests/Uno.Extensions.Hosting.WinUI.Tests.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Uno.Sdk">
+
+	<PropertyGroup>
+		<TargetFramework>net9.0</TargetFramework>
+		<IsPackable>false</IsPackable>
+		<Nullable>disable</Nullable>
+	</PropertyGroup>
+
+	<ItemGroup>
+		<ProjectReference Include="..\Uno.Extensions.Hosting.UI\Uno.Extensions.Hosting.WinUI.csproj" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<PackageReference Include="Moq" />
+		<PackageReference Include="MSTest.TestAdapter"  />
+		<PackageReference Include="MSTest.TestFramework"  />
+		<PackageReference Include="Microsoft.NET.Test.Sdk" />
+		<PackageReference Include="FluentAssertions" />
+	</ItemGroup>
+
+</Project>

src/Uno.Extensions.Hosting.UI/HostBuilder.cs

@@ -1,6 +1,8 @@
 // Marking as auto-generated to prevent StyleCop including this file - Taken from Microsoft.Extensions.Hosting
 // <auto-generated />
 
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
 namespace Uno.Extensions.Hosting;
 
 /// <inheritdoc cref="IHostBuilder" />
@@ -241,6 +243,12 @@ private void CreateServiceProvider()
 		//services.AddOptions().Configure<HostOptions>(options => { options.Initialize(_hostConfiguration); });
 		services.AddLogging();
 
+		var ambientFactory = Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory;
+		if (ambientFactory is not null)
+		{
+			services.Replace(ServiceDescriptor.Singleton(typeof(ILoggerFactory), ambientFactory));
+		}
+
 		foreach (Action<HostBuilderContext, IServiceCollection> configureServicesAction in _configureServicesActions)
 		{
 			configureServicesAction(_hostBuilderContext!, services);

src/Uno.Extensions.Hosting.UI/Uno.Extensions.Hosting.WinUI.csproj

@@ -18,6 +18,7 @@
 
 	<ItemGroup>
 		<PackageReference Include="Microsoft.Extensions.Hosting" />
+		<PackageReference Include="Uno.Core.Extensions.Logging.Singleton" />
 	</ItemGroup>
 
 	<ItemGroup Condition="'$(IsBrowserWasm)'!='true'">

src/Uno.Extensions.Logging/HostBuilderExtensions.cs

@@ -48,11 +48,17 @@
 		this IHostBuilder hostBuilder,
 		Action<HostBuilderContext, ILoggingBuilder>? configure = default, bool enableUnoLogging = false)
 	{
+		bool ambientLoggerExists = Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory != null;
 		return hostBuilder
 				.ConfigureLogging((context, builder) =>
 				{
 					if (!context.IsRegistered(nameof(UseLogging)))
 					{
+						if (ambientLoggerExists)
+						{
+							typeof(HostBuilderExtensions).Log().LogWarning($"Uno.Extensions.LogExtensionPoint.AmbientLoggerFactory already configured; ignoring this .UseLogging() invocation.");
+							return;
+						}
 #if __IOS__
 #pragma warning disable CA1416 // Validate platform compatibility: The net8.0 version is not used on older versions of OS
 						builder.AddProvider(new global::Uno.Extensions.Logging.OSLogLoggerProvider());