Register a service class from its own attributes only

src/DependencyModules.SourceGenerator.Impl/Utilities/ServiceModelUtility.cs

@@ -520,7 +520,17 @@ CancellationToken cancellationToken
     {
         var list = new List<ServiceRegistrationModel>();
 
-        foreach (var attributeSyntax in context.Node.DescendantNodes().OfType<AttributeSyntax>())
+        // The declaration's own attributes only. An attribute on a nested class or on a factory
+        // method in this class registers that class or that method, not this one.
+        var attributeLists = context.Node is MemberDeclarationSyntax member
+            ? member.AttributeLists
+            : default;
+
+        foreach (
+            var attributeSyntax in attributeLists.SelectMany(attributeList =>
+                attributeList.Attributes
+            )
+        )
         {
             foreach (var typeDefinition in _attributeTypes)
             {

tests/DependencyModules.Tests/GeneratorTests/NestedServiceAttributeTests.cs

@@ -0,0 +1,81 @@
+using DependencyModules.Tests.Infrastructure;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace DependencyModules.Tests.GeneratorTests;
+
+/// <summary>
+/// A service attribute registers the declaration it is written on. A nested class or a factory
+/// method inside a service class has its own registration and does not add one for the class.
+/// </summary>
+public class NestedServiceAttributeTests
+{
+    [Fact]
+    public void ANestedServiceClass_DoesNotRegisterItsContainingClassAgain()
+    {
+        var assembly = GeneratedAssembly.Create(
+            """
+            using DependencyModules.Runtime.Attributes;
+
+            namespace TestNamespace;
+
+            public interface ICache { }
+
+            public interface IEntry { }
+
+            [SingletonService]
+            public class Cache : ICache
+            {
+                [TransientService]
+                public class Entry : IEntry { }
+            }
+
+            [DependencyModule]
+            public partial class TestModule;
+            """
+        );
+
+        var cache = assembly.Descriptor("ICache");
+
+        Assert.Equal(ServiceLifetime.Singleton, cache.Lifetime);
+        Assert.Equal(ServiceLifetime.Transient, assembly.Descriptor("IEntry").Lifetime);
+
+        var provider = assembly.BuildProvider();
+
+        Assert.Same(
+            provider.GetRequiredService(assembly.Type("ICache")),
+            provider.GetRequiredService(assembly.Type("ICache"))
+        );
+    }
+
+    [Fact]
+    public void AFactoryMethodInAServiceClass_DoesNotRegisterItsContainingClassAgain()
+    {
+        var assembly = GeneratedAssembly.Create(
+            """
+            using DependencyModules.Runtime.Attributes;
+
+            namespace TestNamespace;
+
+            public interface IStore { }
+
+            public interface IClock { }
+
+            public class Clock : IClock { }
+
+            [SingletonService]
+            public class Store : IStore
+            {
+                [ScopedService]
+                public static IClock CreateClock() => new Clock();
+            }
+
+            [DependencyModule]
+            public partial class TestModule;
+            """
+        );
+
+        Assert.Equal(ServiceLifetime.Singleton, assembly.Descriptor("IStore").Lifetime);
+        Assert.Equal(ServiceLifetime.Scoped, assembly.Descriptor("IClock").Lifetime);
+    }
+}