feat: add async-daemon opt-in to AppFoundationOptions

src/AndreGoepel.AppFoundation.Hosting/AppFoundationOptions.cs

@@ -1,5 +1,6 @@
 using AndreGoepel.Marten.Identity.Blazor;
 using JasperFx;
+using JasperFx.Events.Daemon;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.DataProtection;
 using Microsoft.AspNetCore.HttpsPolicy;
@@ -174,4 +175,24 @@ public sealed class AppFoundationOptions
     /// </para>
     /// </summary>
     public IList<DefaultRole> DefaultRoles { get; } = new List<DefaultRole>();
+
+    /// <summary>
+    /// Opt in to Marten's async daemon, which runs async projections and subscriptions
+    /// in-process via a hosted service. Off by default so existing consumers see no
+    /// behavior change. A host with async-only projections/subscriptions (or that wants
+    /// Marten's built-in daemon instead of hand-rolling its own <c>IHostedService</c>
+    /// around <c>IDocumentStore.BuildProjectionDaemonAsync</c>) sets this to
+    /// <c>true</c>; see also <see cref="AsyncDaemonMode"/>.
+    /// </summary>
+    public bool EnableAsyncDaemon { get; set; }
+
+    /// <summary>
+    /// Daemon mode used when <see cref="EnableAsyncDaemon"/> is <c>true</c>, forwarded to
+    /// Marten's <c>AddAsyncDaemon</c>. Defaults to <see cref="DaemonMode.Solo"/> — the
+    /// right choice for a single running instance of the host; a host that runs multiple
+    /// instances and wants leader election for the daemon should set this to
+    /// <see cref="DaemonMode.HotCold"/> instead. Has no effect unless
+    /// <see cref="EnableAsyncDaemon"/> is <c>true</c>.
+    /// </summary>
+    public DaemonMode AsyncDaemonMode { get; set; } = DaemonMode.Solo;
 }

src/AndreGoepel.AppFoundation.Hosting/Initialization.cs

@@ -113,26 +113,33 @@ public static WebApplicationBuilder AddAppFoundation(
 
         builder.Services.AddScoped<IEmailSender<User>, IdentityEmailSender>();
 
-        builder
-            .Services.AddMarten(marten =>
-            {
-                marten.Connection(connectionString);
+        var martenConfiguration = builder.Services.AddMarten(marten =>
+        {
+            marten.Connection(connectionString);
+
+            marten.InitializeIdentity();
 
-                marten.InitializeIdentity();
+            marten.AutoCreateSchemaObjects = schemaCreation;
 
-                marten.AutoCreateSchemaObjects = schemaCreation;
+            // The alias (and table name) is part of the storage contract — existing key ring rows must
+            // resolve under the same name on upgrade.
+            marten
+                .Schema.For<DataProtectionKeyDocument>()
+                .DocumentAlias("dataprotectionkeydocument");
 
-                // The alias (and table name) is part of the storage contract — existing key ring rows must
-                // resolve under the same name on upgrade.
-                marten
-                    .Schema.For<DataProtectionKeyDocument>()
-                    .DocumentAlias("dataprotectionkeydocument");
+            // Every admin-configured settings record shares one table; consuming apps register their own
+            // via AddSettingsDocument<T>().
+            marten.AddSettingsDocument<EmailSettingsDocument>();
+        });
+
+        // Off by default (no behavior change for existing consumers); a host opts in via
+        // AppFoundationOptions.EnableAsyncDaemon when it has async projections/subscriptions to run.
+        if (options.EnableAsyncDaemon)
+        {
+            martenConfiguration.AddAsyncDaemon(options.AsyncDaemonMode);
+        }
 
-                // Every admin-configured settings record shares one table; consuming apps register their own
-                // via AddSettingsDocument<T>().
-                marten.AddSettingsDocument<EmailSettingsDocument>();
-            })
-            .IntegrateWithWolverine();
+        martenConfiguration.IntegrateWithWolverine();
 
         builder.Services.AddMemoryCache();
         builder.Services.AddHttpContextAccessor();

tests/AndreGoepel.AppFoundation.Tests/Hosting/AddAppFoundationAsyncDaemonTests.cs

@@ -0,0 +1,89 @@
+using AndreGoepel.AppFoundation.Hosting;
+using JasperFx.Events.Daemon;
+using Marten;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace AndreGoepel.AppFoundation.Tests.Hosting;
+
+public sealed class AddAppFoundationAsyncDaemonTests
+{
+    [Fact]
+    public void AddAppFoundation_DefaultOptions_LeavesAsyncDaemonDisabled()
+    {
+        // Arrange — EnableAsyncDaemon defaults to false, so existing consumers see no
+        // behavior change until they opt in (#153).
+        var builder = CreateBuilder();
+
+        // Act
+        builder.AddAppFoundation();
+
+        // Assert
+        Assert.Equal(DaemonMode.Disabled, ResolveAsyncMode(builder));
+    }
+
+    [Fact]
+    public void AddAppFoundation_EnableAsyncDaemon_DefaultsToSoloMode()
+    {
+        // Arrange
+        var builder = CreateBuilder();
+
+        // Act
+        builder.AddAppFoundation(options => options.EnableAsyncDaemon = true);
+
+        // Assert
+        Assert.Equal(DaemonMode.Solo, ResolveAsyncMode(builder));
+    }
+
+    [Fact]
+    public void AddAppFoundation_EnableAsyncDaemonWithExplicitMode_UsesThatMode()
+    {
+        // Arrange
+        var builder = CreateBuilder();
+
+        // Act
+        builder.AddAppFoundation(options =>
+        {
+            options.EnableAsyncDaemon = true;
+            options.AsyncDaemonMode = DaemonMode.HotCold;
+        });
+
+        // Assert
+        Assert.Equal(DaemonMode.HotCold, ResolveAsyncMode(builder));
+    }
+
+    [Fact]
+    public void AddAppFoundation_AsyncDaemonModeWithoutEnabling_HasNoEffect()
+    {
+        // Arrange — setting the mode alone must not turn the daemon on; EnableAsyncDaemon
+        // is the single on/off switch.
+        var builder = CreateBuilder();
+
+        // Act
+        builder.AddAppFoundation(options => options.AsyncDaemonMode = DaemonMode.HotCold);
+
+        // Assert
+        Assert.Equal(DaemonMode.Disabled, ResolveAsyncMode(builder));
+    }
+
+    private static DaemonMode ResolveAsyncMode(WebApplicationBuilder builder)
+    {
+        using var provider = builder.Services.BuildServiceProvider();
+        var store = provider.GetRequiredService<IDocumentStore>();
+        return ((StoreOptions)store.Options).Projections.AsyncMode;
+    }
+
+    private static WebApplicationBuilder CreateBuilder()
+    {
+        var builder = WebApplication.CreateBuilder();
+        builder.Configuration.AddInMemoryCollection(
+            new Dictionary<string, string?>
+            {
+                ["ConnectionStrings:appfoundation-database"] =
+                    "Host=localhost;Port=5432;Database=test;Username=u;Password=p",
+            }
+        );
+        return builder;
+    }
+}