feat: reflection-free Type-based APIs through a slim source generator

src/LocalStack.Client.Extensions/LocalStack.Client.Extensions.csproj

@@ -2,6 +2,7 @@
 
     <PropertyGroup>
         <TargetFrameworks>$(LocalStackExtensionsTargetFrameworks)</TargetFrameworks>
+        <IsAotCompatible>$(IsLocalStackModernTarget)</IsAotCompatible>
         <AssemblyName>LocalStack.Client.Extensions</AssemblyName>
         <RootNamespace>LocalStack.Client.Extensions</RootNamespace>
         <Version>$(PackageExtensionVersion)</Version>

src/LocalStack.Client/LocalStack.Client.csproj

@@ -2,6 +2,7 @@
 
 	<PropertyGroup>
 		<TargetFrameworks>$(LocalStackClientTargetFrameworks)</TargetFrameworks>
+		<IsAotCompatible>$(IsLocalStackModernTarget)</IsAotCompatible>
 		<AssemblyName>LocalStack.Client</AssemblyName>
 		<RootNamespace>LocalStack.Client</RootNamespace>
 

src/LocalStack.Client/Properties/AssemblyInfo.cs

@@ -1,3 +1,5 @@
 using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("LocalStack.Client.Extensions")]
+[assembly: InternalsVisibleTo("LocalStack.Client.Tests")]
+[assembly: InternalsVisibleTo("LocalStack.Client.Integration.Tests")]

src/LocalStack.Client/Session.cs

@@ -8,7 +8,7 @@ public class Session : ISession
     private readonly ISessionOptions _sessionOptions;
     private readonly ISessionReflection _sessionReflection;
 
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
     [DynamicDependency(nameof(RegisterGeneratedClient), typeof(Session))]
     [DynamicDependency(nameof(RegisterGeneratedConfig), typeof(Session))]
 #endif
@@ -56,6 +56,13 @@ public AmazonServiceClient CreateClientByImplementation(
             clientConfig.RegionEndpoint = RegionEndpoint.GetBySystemName(_sessionOptions.RegionName);
         }
 
+#if NET10_0_OR_GREATER
+        if (implType == null)
+        {
+            throw new ArgumentNullException(nameof(implType));
+        }
+#endif
+
         var clientInstance = CreateImplementation(implType, awsCredentials, clientConfig);
 
         return clientInstance;
@@ -84,7 +91,7 @@ public AmazonServiceClient CreateClientByInterface(
         }
 
         var clientTypeName = $"{serviceInterfaceType.Namespace}.{serviceInterfaceType.Name.Substring(1)}Client";
-        Type? clientType = FindClientType(serviceInterfaceType.GetTypeInfo().Assembly, clientTypeName);
+        Type? clientType = FindClientType(serviceInterfaceType.Assembly, clientTypeName);
 
         if (clientType == null)
         {
@@ -119,17 +126,15 @@ public AmazonServiceClient CreateClientByInterface(
             clientConfig.RegionEndpoint = RegionEndpoint.GetBySystemName(_sessionOptions.RegionName);
         }
 
-        ConstructorInfo? constructor = FindClientConstructor(clientType, clientConfig.GetType());
+        AmazonServiceClient? client = CreateInterface(clientType, awsCredentials, clientConfig);
 
-        if (constructor == null)
+        if (client == null)
         {
             var message = $"Service client {clientTypeName} missing a constructor with parameters AWSCredentials and {clientConfig.GetType().FullName}.";
 
             throw new AmazonClientException(message);
         }
 
-        var client = (AmazonServiceClient)constructor.Invoke(new object[] { awsCredentials, clientConfig });
-
         return client;
     }
 
@@ -177,72 +182,103 @@ private AmazonServiceClient CreateClientByStaticFactory<TClient>(bool useService
 
     private static Type? FindClientType(Assembly assembly, string name)
     {
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
         Type? generated = GeneratedClientRegistry.FindClient(assembly, name);
-        if (generated != null || !System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported)
+        if (generated != null)
         {
             return generated;
         }
-#endif
+        if (ReflectionFallback.IsSupported)
+        {
+            return FindLegacyClientType(assembly, name);
+        }
+
+        return null;
+#else
         return FindLegacyClientType(assembly, name);
+#endif
     }
 
-    private static ConstructorInfo? FindClientConstructor(Type type, Type configType)
+    private static AmazonServiceClient? CreateInterface(Type type, AWSCredentials credentials, ClientConfig config)
     {
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
         if (GeneratedClientRegistry.TryGetClient(type, out GeneratedClientRegistry.ClientEntry? entry))
         {
-            return entry.Constructor(configType);
+            return CreateGenerated(entry, credentials, config);
         }
 
-        if (!System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported)
+        if (ReflectionFallback.IsSupported)
+        {
+            return CreateLegacyInterface(type, credentials, config);
+        }
+        else
         {
             return null;
         }
+#else
+        return CreateLegacyInterface(type, credentials, config);
 #endif
-        return FindLegacyClientConstructor(type, configType);
     }
 
     private static AmazonServiceClient CreateImplementation(Type type, AWSCredentials credentials, ClientConfig config)
     {
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
         if (GeneratedClientRegistry.TryGetClient(type, out GeneratedClientRegistry.ClientEntry? entry))
         {
-            return entry.Create(credentials, config);
+            return CreateGenerated(entry, credentials, config)
+                ?? throw new MissingMethodException($"Constructor on type '{type.FullName}' not found.");
         }
 
-        if (!System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported)
+        if (ReflectionFallback.IsSupported)
+        {
+            return CreateLegacyImplementation(type, credentials, config);
+        }
+        else
         {
             throw new NotSupportedException($"Client type {type} was not present when the application was compiled.");
         }
-#endif
+#else
         return CreateLegacyImplementation(type, credentials, config);
+#endif
     }
 
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
     [RequiresUnreferencedCode("Dynamically loaded client types require their original reflection metadata.")]
 #endif
     private static Type? FindLegacyClientType(Assembly assembly, string name) => assembly.GetType(name);
 
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
     [RequiresUnreferencedCode("Dynamically loaded client constructors require their original reflection metadata.")]
 #endif
-    private static ConstructorInfo? FindLegacyClientConstructor(Type type, Type configType) => type.GetConstructor(new[] { typeof(AWSCredentials), configType });
+    private static AmazonServiceClient? CreateLegacyInterface(Type type, AWSCredentials credentials, ClientConfig config) =>
+        (AmazonServiceClient?)type.GetConstructor(new[] { typeof(AWSCredentials), config.GetType() })?.Invoke(new object[] { credentials, config });
+
+#if NET10_0_OR_GREATER
+    private static AmazonServiceClient? CreateGenerated(GeneratedClientRegistry.ClientEntry entry, AWSCredentials credentials, ClientConfig config)
+    {
+        try
+        {
+            return entry.Create(credentials, config);
+        }
+        catch (Exception exception)
+        {
+            throw new TargetInvocationException(exception);
+        }
+    }
 
-#if NET8_0_OR_GREATER
     [RequiresUnreferencedCode("Dynamically loaded client constructors require their original reflection metadata.")]
 #endif
     private static AmazonServiceClient CreateLegacyImplementation(Type type, AWSCredentials credentials, ClientConfig config) =>
         (AmazonServiceClient)Activator.CreateInstance(type, credentials, config)!;
 
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
     // The generated caller uses UnsafeAccessor. Only delegates cross this boundary: no DAM
     // requirements are imposed on an accessor signature or on existing consumer Type APIs.
     private static void RegisterGeneratedClient(Type type, Func<IServiceMetadata> metadata, Func<ClientConfig> config,
-                                                Func<Type, ConstructorInfo?> constructor, Func<AWSCredentials, ClientConfig, AmazonServiceClient> create) =>
-        GeneratedClientRegistry.RegisterClient(type, metadata, config, constructor, create);
+                                                Func<AWSCredentials, ClientConfig, AmazonServiceClient?> create) =>
+        GeneratedClientRegistry.RegisterClient(type, metadata, config, create);
 
-    private static void RegisterGeneratedConfig(Type type, Func<ClientConfig, bool, bool> style, Action<object, string> region) =>
-        GeneratedClientRegistry.RegisterConfig(type, style, region);
+    private static void RegisterGeneratedConfig(Type type, Func<ClientConfig, bool, bool>? style, bool plainRegion) =>
+        GeneratedClientRegistry.RegisterConfig(type, style, plainRegion);
 #endif
 }

src/LocalStack.Client/Utils/GeneratedClientRegistry.cs

@@ -1,4 +1,4 @@
-#if NET8_0_OR_GREATER
+#if NET10_0_OR_GREATER
 using System.Collections.Concurrent;
 
 namespace LocalStack.Client.Utils;
@@ -12,17 +12,17 @@ internal static class GeneratedClientRegistry
     private static readonly ConcurrentDictionary<Type, ConfigEntry> Configs = new();
 
     public static void RegisterClient(Type type, Func<IServiceMetadata> metadata, Func<ClientConfig> config,
-                                      Func<Type, ConstructorInfo?> constructor, Func<AWSCredentials, ClientConfig, AmazonServiceClient> create)
+                                      Func<AWSCredentials, ClientConfig, AmazonServiceClient?> create)
     {
-        Clients.TryAdd(type, new ClientEntry(metadata, config, constructor, create));
+        Clients.TryAdd(type, new ClientEntry(metadata, config, create));
         if (type.FullName is string name)
         {
             ClientNames.TryAdd((type.Assembly, name), type);
         }
     }
 
-    public static void RegisterConfig(Type type, Func<ClientConfig, bool, bool> style, Action<object, string> region) =>
-        Configs.TryAdd(type, new ConfigEntry(style, region));
+    public static void RegisterConfig(Type type, Func<ClientConfig, bool, bool>? style, bool plainRegion) =>
+        Configs.TryAdd(type, new ConfigEntry(style, plainRegion));
 
     public static Type? FindClient(Assembly assembly, string name) => ClientNames.TryGetValue((assembly, name), out Type? type) ? type : null;
 
@@ -34,9 +34,9 @@ public static bool TryGetClient(Type type, [NotNullWhen(true)] out ClientEntry?
 
     public static bool TryGetConfig(Type type, [NotNullWhen(true)] out ConfigEntry? entry) => Configs.TryGetValue(type, out entry);
 
-    internal sealed record ClientEntry(Func<IServiceMetadata> Metadata, Func<ClientConfig> Config, Func<Type, ConstructorInfo?> Constructor,
-                                       Func<AWSCredentials, ClientConfig, AmazonServiceClient> Create);
+    internal sealed record ClientEntry(Func<IServiceMetadata> Metadata, Func<ClientConfig> CreateConfig,
+                                       Func<AWSCredentials, ClientConfig, AmazonServiceClient?> Create);
 
-    internal sealed record ConfigEntry(Func<ClientConfig, bool, bool> Style, Action<object, string> Region);
+    internal sealed record ConfigEntry(Func<ClientConfig, bool, bool>? Style, bool PlainRegion);
 }
 #endif

src/LocalStack.Client/Utils/ReflectionFallback.cs

@@ -0,0 +1,10 @@
+namespace LocalStack.Client.Utils;
+
+internal static class ReflectionFallback
+{
+#if NET10_0_OR_GREATER
+    [FeatureGuard(typeof(RequiresUnreferencedCodeAttribute))]
+#endif
+    internal static bool IsSupported { get; } =
+        !AppContext.TryGetSwitch("LocalStack.Client.ReflectionFallback.IsSupported", out bool enabled) || enabled;
+}