Add support for service key registration

Introduced service key registration in the `ILifetimeSelector` interface with two new methods: `WithServiceKey(object serviceKey)` and `WithServiceKey(Func<Type, object?> selector)`. These enable registering services with fixed or dynamically determined service keys.

Updated the `LifetimeSelector` class to handle service key functionality, including adding the `ServiceKeySelectorFn` property, modifying the `Populate` method to support keyed `ServiceDescriptor` creation, and adding helper methods for service key resolution.

Enhanced the `ServiceTypeSelector` class to propagate service key selectors to `LifetimeSelector` instances.

Added unit tests in `ScanningTests.cs` to validate service key registration and resolution, including tests for fixed keys, selector-based keys, and keyed service resolution.

Made minor formatting adjustments and ensured proper validation of the new functionality.

Author: mokarchi

src/Scrutor/ILifetimeSelector.cs

@@ -1,5 +1,5 @@
-using System;
-using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection;
+using System;
 
 namespace Scrutor;
 
@@ -29,4 +29,16 @@ public interface ILifetimeSelector : IServiceTypeSelector
     /// Registers each matching concrete type with a lifetime based on the provided <paramref name="selector"/>.
     /// </summary>
     IImplementationTypeSelector WithLifetime(Func<Type, ServiceLifetime> selector);
+
+    /// <summary>
+    /// Registers each matching concrete type with the specified <paramref name="serviceKey"/>.
+    /// </summary>
+    /// <param name="serviceKey">The service key to use for registration.</param>
+    ILifetimeSelector WithServiceKey(object serviceKey);
+
+    /// <summary>
+    /// Registers each matching concrete type with a service key based on the provided <paramref name="selector"/>.
+    /// </summary>
+    /// <param name="selector">A function to determine the service key for each type.</param>
+    ILifetimeSelector WithServiceKey(Func<Type, object?> selector);
 }

src/Scrutor/LifetimeSelector.cs

@@ -1,9 +1,9 @@
-using System;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyModel;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.DependencyModel;
 
 namespace Scrutor;
 
@@ -24,6 +24,8 @@ public LifetimeSelector(ServiceTypeSelector inner, IEnumerable<TypeMap> typeMaps
 
     public Func<Type, ServiceLifetime>? SelectorFn { get; set; }
 
+    public Func<Type, object?>? ServiceKeySelectorFn { get; set; }
+
     public IImplementationTypeSelector WithSingletonLifetime()
     {
         return WithLifetime(ServiceLifetime.Singleton);
@@ -54,6 +56,22 @@ public IImplementationTypeSelector WithLifetime(Func<Type, ServiceLifetime> sele
         return this;
     }
 
+    public ILifetimeSelector WithServiceKey(object serviceKey)
+    {
+        Preconditions.NotNull(serviceKey, nameof(serviceKey));
+
+        return WithServiceKey(_ => serviceKey);
+    }
+
+    public ILifetimeSelector WithServiceKey(Func<Type, object?> selector)
+    {
+        Preconditions.NotNull(selector, nameof(selector));
+
+        Inner.PropagateServiceKey(selector);
+
+        return this;
+    }
+
     #region Chain Methods
 
     [ExcludeFromCodeCoverage]
@@ -231,6 +249,7 @@ void ISelector.Populate(IServiceCollection services, RegistrationStrategy? strat
         strategy ??= RegistrationStrategy.Append;
 
         var lifetimes = new Dictionary<Type, ServiceLifetime>();
+        var serviceKeys = new Dictionary<Type, object?>();
 
         foreach (var typeMap in TypeMaps)
         {
@@ -244,8 +263,10 @@ void ISelector.Populate(IServiceCollection services, RegistrationStrategy? strat
                 }
 
                 var lifetime = GetOrAddLifetime(lifetimes, implementationType);
-
-                var descriptor = new ServiceDescriptor(serviceType, implementationType, lifetime);
+                var serviceKey = GetOrAddServiceKey(serviceKeys, implementationType);
+                var descriptor = serviceKey is not null
+                    ? new ServiceDescriptor(serviceType, serviceKey, implementationType, lifetime)
+                    : new ServiceDescriptor(serviceType, implementationType, lifetime);
 
                 strategy.Apply(services, descriptor);
             }
@@ -256,8 +277,11 @@ void ISelector.Populate(IServiceCollection services, RegistrationStrategy? strat
             foreach (var serviceType in typeFactoryMap.ServiceTypes)
             {
                 var lifetime = GetOrAddLifetime(lifetimes, typeFactoryMap.ImplementationType);
+                var serviceKey = GetOrAddServiceKey(serviceKeys, typeFactoryMap.ImplementationType);
 
-                var descriptor = new ServiceDescriptor(serviceType, typeFactoryMap.ImplementationFactory, lifetime);
+                var descriptor = serviceKey is not null
+                    ? new ServiceDescriptor(serviceType, serviceKey, WrapImplementationFactory(typeFactoryMap.ImplementationFactory), lifetime)
+                    : new ServiceDescriptor(serviceType, typeFactoryMap.ImplementationFactory, lifetime);
 
                 strategy.Apply(services, descriptor);
             }
@@ -277,4 +301,23 @@ private ServiceLifetime GetOrAddLifetime(Dictionary<Type, ServiceLifetime> lifet
 
         return lifetime;
     }
+
+    private object? GetOrAddServiceKey(Dictionary<Type, object?> serviceKeys, Type implementationType)
+    {
+        if (serviceKeys.TryGetValue(implementationType, out var serviceKey))
+        {
+            return serviceKey;
+        }
+
+        serviceKey = ServiceKeySelectorFn?.Invoke(implementationType);
+
+        serviceKeys[implementationType] = serviceKey;
+
+        return serviceKey;
+    }
+
+    private static Func<IServiceProvider, object?, object> WrapImplementationFactory(Func<IServiceProvider, object> factory)
+    {
+        return (sp, _) => factory(sp);
+    }
 }

src/Scrutor/ServiceTypeSelector.cs

@@ -1,10 +1,10 @@
-using System;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyModel;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.DependencyModel;
 
 namespace Scrutor;
 
@@ -207,6 +207,14 @@ internal void PropagateLifetime(Func<Type, ServiceLifetime> selectorFn)
         }
     }
 
+    internal void PropagateServiceKey(Func<Type, object?> selectorFn)
+    {
+        foreach (var selector in Selectors.OfType<LifetimeSelector>())
+        {
+            selector.ServiceKeySelectorFn = selectorFn;
+        }
+    }
+
     void ISelector.Populate(IServiceCollection services, RegistrationStrategy? registrationStrategy)
     {
         if (Selectors.Count == 0)

test/Scrutor.Tests/ScanningTests.cs

@@ -584,10 +584,70 @@ public void ShouldAllowOptInToCompilerGeneratedTypes()
                     .AsSelf()
                     .WithTransientLifetime());
             });
-            
+
             var compilerGeneratedSubclass = provider.GetService<AllowedCompilerGeneratedSubclass>();
             Assert.NotNull(compilerGeneratedSubclass);
         }
+
+        [Fact]
+        public void CanRegisterWithServiceKey()
+        {
+            Collection.Scan(scan => scan
+                .FromTypes<TransientService1, TransientService2>()
+                    .AsImplementedInterfaces(x => x != typeof(IOtherInheritance))
+                    .WithServiceKey("my-key")
+                    .WithSingletonLifetime());
+
+            Assert.Equal(2, Collection.Count);
+
+            Assert.All(Collection, x =>
+            {
+                Assert.Equal(ServiceLifetime.Singleton, x.Lifetime);
+                Assert.Equal(typeof(ITransientService), x.ServiceType);
+                Assert.True(x.IsKeyedService);
+                Assert.Equal("my-key", x.ServiceKey);
+            });
+        }
+
+        [Fact]
+        public void CanRegisterWithServiceKeySelector()
+        {
+            Collection.Scan(scan => scan
+                .FromTypes<TransientService1, TransientService2>()
+                    .AsImplementedInterfaces(x => x != typeof(IOtherInheritance))
+                    .WithServiceKey(type => type.Name)
+                    .WithSingletonLifetime());
+
+            Assert.Equal(2, Collection.Count);
+
+            var service1 = Collection.First(x => x.ServiceKey as string == nameof(TransientService1));
+            Assert.Equal(typeof(ITransientService), service1.ServiceType);
+            Assert.Equal(ServiceLifetime.Singleton, service1.Lifetime);
+            Assert.True(service1.IsKeyedService);
+
+            var service2 = Collection.First(x => x.ServiceKey as string == nameof(TransientService2));
+            Assert.Equal(typeof(ITransientService), service2.ServiceType);
+            Assert.Equal(ServiceLifetime.Singleton, service2.Lifetime);
+            Assert.True(service2.IsKeyedService);
+        }
+
+        [Fact]
+        public void CanResolveKeyedServices()
+        {
+            Collection.Scan(scan => scan
+                .FromTypes<TransientService1, TransientService2>()
+                    .AsSelf()
+                    .WithServiceKey(type => type.Name)
+                    .WithTransientLifetime());
+
+            var provider = Collection.BuildServiceProvider();
+
+            var service1 = provider.GetRequiredKeyedService<TransientService1>(nameof(TransientService1));
+            var service2 = provider.GetRequiredKeyedService<TransientService2>(nameof(TransientService2));
+
+            Assert.NotNull(service1);
+            Assert.NotNull(service2);
+        }
     }
 
     // ReSharper disable UnusedTypeParameter
@@ -671,7 +731,7 @@ public class DefaultAttributes : IDefault3Level2, IDefault1, IDefault2 { }
     [CompilerGenerated]
     public class CompilerGenerated { }
 
-    public class CombinedService2: IDefault1, IDefault2, IDefault3Level2 { }
+    public class CombinedService2 : IDefault1, IDefault2, IDefault3Level2 { }
 
     public interface IGenericAttribute { }