fix(hosting): start the SDK during Build() even when the app clears or replaces logger providers

src/Sentry.Extensions.Hosting/Sentry.Extensions.Hosting.csproj

@@ -20,6 +20,12 @@
 
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'">
     <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="3.1.0" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" Version="3.1.0" />
+  </ItemGroup>
+
+  <!-- The lowest version with HostOptions: a per-runtime version makes apps that reference an older Microsoft.Extensions.Hosting fail with NU1605 -->
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' And '$(TargetFrameworkVersion)' == 'v8.0'">

src/Sentry.Extensions.Hosting/SentryHostBuilderExtensions.cs

@@ -183,6 +183,7 @@ private static void AddSentryGenericHostServices(
             : new SentryStructuredLoggerProvider(c.GetRequiredService<IHub>()));
         services.TryAddSingleton<HostLoggerProvidersMarker>();
         services.AddSentry<SentryGenericHostOptions>();
+        services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<HostOptions>, SentrySdkInitializer>());
         services.TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService, SentryHostedService>(c =>
             new SentryHostedService(c, app == App.Web && !HasHostIntegration(services))));
 

src/Sentry.Extensions.Hosting/SentrySdkInitializer.cs

@@ -0,0 +1,14 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Options;
+
+namespace Sentry.Extensions.Hosting;
+
+/// <summary>
+/// Starts the SDK while the host is built. The host's constructor reads <c>IOptions&lt;HostOptions&gt;</c>, which runs
+/// this, so the SDK starts even when the app removes or replaces Sentry's logger providers.
+/// </summary>
+internal sealed class SentrySdkInitializer(IServiceProvider services) : IConfigureOptions<HostOptions>
+{
+    public void Configure(HostOptions options) => _ = services.GetRequiredService<Func<IHub>>();
+}

test/Sentry.Extensions.Hosting.Tests/SentryHostBuilderExtensionsTests.cs

@@ -2,6 +2,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using Sentry.Extensions.Logging;
 
@@ -297,6 +298,30 @@ public void UseSentry_CapturedEvent_ReportsHostingSdk(BuilderKind kind)
         sdk.Packages.Should().Contain(package => package.Name == "nuget:Sentry.Extensions.Hosting");
     }
 
+    [Theory, MemberData(nameof(TestHost.Builders), MemberType = typeof(TestHost))]
+    public void UseSentry_LoggerProvidersClearedAfterwards_CapturesBeforeHostStarts(BuilderKind kind)
+    {
+        var testHost = new TestHost().UseSentry(Capture).ClearLoggerProviders();
+        using var host = testHost.Build(kind);
+
+        SentrySdk.CaptureMessage("captured before the host starts");
+
+        _events.Should().ContainSingle(e => e.Message!.Message == "captured before the host starts");
+    }
+
+    [Theory, MemberData(nameof(TestHost.Builders), MemberType = typeof(TestHost))]
+    public void UseSentry_LoggerFactoryReplaced_CapturesBeforeHostStarts(BuilderKind kind)
+    {
+        var testHost = new TestHost()
+            .UseSentry(Capture)
+            .ConfigureServices(services => services.AddSingleton<ILoggerFactory>(NullLoggerFactory.Instance));
+        using var host = testHost.Build(kind);
+
+        SentrySdk.CaptureMessage("captured before the host starts");
+
+        _events.Should().ContainSingle(e => e.Message!.Message == "captured before the host starts");
+    }
+
     [Theory, MemberData(nameof(TestHost.Builders), MemberType = typeof(TestHost))]
     public async Task UseSentry_EmptyDsnInJson_StartsHostWithSentryDisabled(BuilderKind kind)
     {

test/Sentry.Extensions.Hosting.Tests/SentryHostedServiceTests.cs

@@ -74,14 +74,18 @@ public async Task StartAsync_WorkerHost_LogsNoWarning(BuilderKind kind)
         standardError.ToString().Should().NotContain("Sentry:");
     }
 
+    private static void RemoveSdkInitializer(IServiceCollection services)
+        => services.Remove(services.Single(d => d.ImplementationType == typeof(SentrySdkInitializer)));
+
     [Theory, MemberData(nameof(TestHost.Builders), MemberType = typeof(TestHost))]
-    public async Task StartAsync_LoggerProvidersCleared_SdkRunsBeforeAppHostedServiceStarts(BuilderKind kind)
+    public async Task StartAsync_SdkNotStartedDuringBuild_SdkRunsBeforeAppHostedServiceStarts(BuilderKind kind)
     {
         var appService = new SdkStateAtStart();
         var testHost = new TestHost()
             .ConfigureServices(services => services.AddSingleton<IHostedService>(appService))
             .UseSentry(Capture)
-            .ClearLoggerProviders();
+            .ClearLoggerProviders()
+            .ConfigureServices(RemoveSdkInitializer);
         using var host = testHost.Build(kind);
         SentrySdk.IsEnabled.Should().BeFalse();
 
@@ -93,7 +97,7 @@ public async Task StartAsync_LoggerProvidersCleared_SdkRunsBeforeAppHostedServic
 
 #if NET8_0_OR_GREATER
     [Theory, MemberData(nameof(TestHost.Builders), MemberType = typeof(TestHost))]
-    public async Task StartAsync_ServicesStartConcurrently_SdkRunsBeforeAppHostedServiceStarts(BuilderKind kind)
+    public async Task StartAsync_SdkNotStartedDuringBuildAndServicesStartConcurrently_SdkRunsBeforeAppHostedServiceStarts(BuilderKind kind)
     {
         var appService = new SdkStateAtStart();
         var testHost = new TestHost()
@@ -103,7 +107,8 @@ public async Task StartAsync_ServicesStartConcurrently_SdkRunsBeforeAppHostedSer
                 services.AddSingleton<IHostedService>(appService);
             })
             .UseSentry(Capture)
-            .ClearLoggerProviders();
+            .ClearLoggerProviders()
+            .ConfigureServices(RemoveSdkInitializer);
         using var host = testHost.Build(kind);
         SentrySdk.IsEnabled.Should().BeFalse();