Make the .NET library NativeAOT compatible

- Enabled AOT analyzers
- Disabled STJ reflection in the test project (to help vet NAOT correctness)
- Use source generation for all types that may be serialized
- Remove all use of anonymous types
- Removed <autogenerated/> from the source generated code, as it was suppressing the analyzers
- Added support for propagating StreamJsonRpc's tracing to the CopilotClient's ILogger. I used this for debugging and decided to leave it
- Updated StreamJsonRpc to a newly published version on nuget to pick up NativeAOT fixes
- Cleaned up some formatting in the session types generator, in particular using a file-scoped namespace and removing the top-level indentation

Author: stephentoub

dotnet/src/Client.cs

@@ -49,7 +49,7 @@ namespace GitHub.Copilot.SDK;
 /// await session.SendAsync(new MessageOptions { Prompt = "Hello!" });
 /// </code>
 /// </example>
-public class CopilotClient : IDisposable, IAsyncDisposable
+public partial class CopilotClient : IDisposable, IAsyncDisposable
 {
     private readonly ConcurrentDictionary<string, CopilotSession> _sessions = new();
     private readonly CopilotClientOptions _options;
@@ -461,7 +461,7 @@ public async Task<PingResponse> PingAsync(string? message = null, CancellationTo
         var connection = await EnsureConnectedAsync(cancellationToken);
 
         return await connection.Rpc.InvokeWithCancellationAsync<PingResponse>(
-            "ping", [new { message }], cancellationToken);
+            "ping", [new PingRequest { Message = message }], cancellationToken);
     }
 
     /// <summary>
@@ -510,7 +510,7 @@ public async Task DeleteSessionAsync(string sessionId, CancellationToken cancell
         var connection = await EnsureConnectedAsync(cancellationToken);
 
         var response = await connection.Rpc.InvokeWithCancellationAsync<DeleteSessionResponse>(
-            "session.delete", [new { sessionId }], cancellationToken);
+            "session.delete", [new DeleteSessionRequest(sessionId)], cancellationToken);
 
         if (!response.Success)
         {
@@ -560,7 +560,7 @@ private async Task VerifyProtocolVersionAsync(Connection connection, Cancellatio
     {
         var expectedVersion = SdkProtocolVersion.GetVersion();
         var pingResponse = await connection.Rpc.InvokeWithCancellationAsync<PingResponse>(
-            "ping", [new { message = (string?)null }], cancellationToken);
+            "ping", [new PingRequest()], cancellationToken);
 
         if (!pingResponse.ProtocolVersion.HasValue)
         {
@@ -710,23 +710,45 @@ private async Task<Connection> ConnectToServerAsync(Process? cliProcess, string?
             outputStream = networkStream;
         }
 
-        var rpc = new JsonRpc(new HeaderDelimitedMessageHandler(outputStream, inputStream, CreateFormatter()));
-        rpc.AddLocalRpcTarget(new RpcHandler(this));
+        var rpc = new JsonRpc(new HeaderDelimitedMessageHandler(
+            outputStream,
+            inputStream,
+            CreateSystemTextJsonFormatter()))
+        {
+            TraceSource = new LoggerTraceSource(_logger),
+        };
+
+        var handler = new RpcHandler(this);
+        rpc.AddLocalRpcMethod("session.event", handler.OnSessionEvent);
+        rpc.AddLocalRpcMethod("tool.call", handler.OnToolCall);
+        rpc.AddLocalRpcMethod("permission.request", handler.OnPermissionRequest);
         rpc.StartListening();
         return new Connection(rpc, cliProcess, tcpClient, networkStream);
     }
 
-    [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "Using the Json source generator.")]
-    [UnconditionalSuppressMessage("AOT", "IL3050", Justification = "Using the Json source generator.")]
-    static IJsonRpcMessageFormatter CreateFormatter()
+    [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "Using happy path from https://microsoft.github.io/vs-streamjsonrpc/docs/nativeAOT.html")]
+    [UnconditionalSuppressMessage("AOT", "IL3050", Justification = "Using happy path from https://microsoft.github.io/vs-streamjsonrpc/docs/nativeAOT.html")]
+    private static SystemTextJsonFormatter CreateSystemTextJsonFormatter() =>
+        new SystemTextJsonFormatter() { JsonSerializerOptions = SerializerOptionsForMessageFormatter };
+
+    private static JsonSerializerOptions SerializerOptionsForMessageFormatter { get; } = CreateSerializerOptions();
+
+    private static JsonSerializerOptions CreateSerializerOptions()
     {
         var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
         {
             AllowOutOfOrderMetadataProperties = true,
             DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
         };
 
-        return new SystemTextJsonFormatter() { JsonSerializerOptions = options };
+        options.TypeInfoResolverChain.Add(ClientJsonContext.Default);
+        options.TypeInfoResolverChain.Add(TypesJsonContext.Default);
+        options.TypeInfoResolverChain.Add(CopilotSession.SessionJsonContext.Default);
+        options.TypeInfoResolverChain.Add(SessionEventsJsonContext.Default);
+
+        options.MakeReadOnly();
+
+        return options;
     }
 
     internal CopilotSession? GetSession(string sessionId) =>
@@ -759,9 +781,7 @@ public async ValueTask DisposeAsync()
 
     private class RpcHandler(CopilotClient client)
     {
-        [JsonRpcMethod("session.event")]
-        public void OnSessionEvent(string sessionId,
-            JsonElement? @event)
+        public void OnSessionEvent(string sessionId, JsonElement? @event)
         {
             var session = client.GetSession(sessionId);
             if (session != null && @event != null)
@@ -774,7 +794,6 @@ public void OnSessionEvent(string sessionId,
             }
         }
 
-        [JsonRpcMethod("tool.call")]
         public async Task<ToolCallResponse> OnToolCall(string sessionId,
             string toolCallId,
             string toolName,
@@ -847,7 +866,7 @@ public async Task<ToolCallResponse> OnToolCall(string sessionId,
                     // something we don't control? an error?)
                     TextResultForLlm = result is JsonElement { ValueKind: JsonValueKind.String } je
                         ? je.GetString()!
-                        : JsonSerializer.Serialize(result, tool.JsonSerializerOptions),
+                        : JsonSerializer.Serialize(result, tool.JsonSerializerOptions.GetTypeInfo(typeof(object))),
                 };
                 return new ToolCallResponse(toolResultObject);
             }
@@ -864,7 +883,6 @@ public async Task<ToolCallResponse> OnToolCall(string sessionId,
             }
         }
 
-        [JsonRpcMethod("permission.request")]
         public async Task<PermissionRequestResponse> OnPermissionRequest(string sessionId, JsonElement permissionRequest)
         {
             var session = client.GetSession(sessionId);
@@ -915,7 +933,7 @@ public static string Escape(string arg)
     }
 
     // Request/Response types for RPC
-    private record CreateSessionRequest(
+    internal record CreateSessionRequest(
         string? Model,
         string? SessionId,
         List<ToolDefinition>? Tools,
@@ -931,7 +949,7 @@ private record CreateSessionRequest(
         List<string>? SkillDirectories,
         List<string>? DisabledSkills);
 
-    private record ToolDefinition(
+    internal record ToolDefinition(
         string Name,
         string? Description,
         JsonElement Parameters /* JSON schema */)
@@ -940,10 +958,10 @@ public static ToolDefinition FromAIFunction(AIFunction function)
             => new ToolDefinition(function.Name, function.Description, function.JsonSchema);
     }
 
-    private record CreateSessionResponse(
+    internal record CreateSessionResponse(
         string SessionId);
 
-    private record ResumeSessionRequest(
+    internal record ResumeSessionRequest(
         string SessionId,
         List<ToolDefinition>? Tools,
         ProviderConfig? Provider,
@@ -954,24 +972,93 @@ private record ResumeSessionRequest(
         List<string>? SkillDirectories,
         List<string>? DisabledSkills);
 
-    private record ResumeSessionResponse(
+    internal record ResumeSessionResponse(
         string SessionId);
 
-    private record GetLastSessionIdResponse(
+    internal record GetLastSessionIdResponse(
         string? SessionId);
 
-    private record DeleteSessionResponse(
+    internal record DeleteSessionRequest(
+        string SessionId);
+
+    internal record DeleteSessionResponse(
         bool Success,
         string? Error);
 
-    private record ListSessionsResponse(
+    internal record ListSessionsResponse(
         List<SessionMetadata> Sessions);
 
-    private record ToolCallResponse(
+    internal record ToolCallResponse(
         ToolResultObject? Result);
 
-    private record PermissionRequestResponse(
+    internal record PermissionRequestResponse(
         PermissionRequestResult Result);
+
+    /// <summary>Trace source that forwards all logs to the ILogger.</summary>
+    internal sealed class LoggerTraceSource : TraceSource
+    {
+        public LoggerTraceSource(ILogger logger) : base(nameof(LoggerTraceSource), SourceLevels.All)
+        {
+            Listeners.Clear();
+            Listeners.Add(new LoggerTraceListener(logger));
+        }
+
+        private sealed class LoggerTraceListener(ILogger logger) : TraceListener
+        {
+            public override void TraceEvent(TraceEventCache? eventCache, string source, TraceEventType eventType, int id, string? message) =>
+                logger.Log(MapLevel(eventType), "[{Source}] {Message}", source, message);
+
+            public override void TraceEvent(TraceEventCache? eventCache, string source, TraceEventType eventType, int id, string? format, params object?[]? args) => 
+                logger.Log(MapLevel(eventType), "[{Source}] {Message}", source, args is null || args.Length == 0 ? format : string.Format(format ?? "", args));
+
+            public override void TraceData(TraceEventCache? eventCache, string source, TraceEventType eventType, int id, object? data) => 
+                logger.Log(MapLevel(eventType), "[{Source}] {Data}", source, data);
+
+            public override void TraceData(TraceEventCache? eventCache, string source, TraceEventType eventType, int id, params object?[]? data) => 
+                logger.Log(MapLevel(eventType), "[{Source}] {Data}", source, data is null ? null : string.Join(", ", data));
+
+            public override void Write(string? message) => 
+                logger.LogTrace("{Message}", message);
+
+            public override void WriteLine(string? message) =>
+                logger.LogTrace("{Message}", message);
+
+            private static LogLevel MapLevel(TraceEventType eventType) => eventType switch
+            {
+                TraceEventType.Critical => LogLevel.Critical,
+                TraceEventType.Error => LogLevel.Error,
+                TraceEventType.Warning => LogLevel.Warning,
+                TraceEventType.Information => LogLevel.Information,
+                TraceEventType.Verbose => LogLevel.Debug,
+                _ => LogLevel.Trace
+            };
+        }
+    }
+
+    [JsonSourceGenerationOptions(
+        JsonSerializerDefaults.Web,
+        AllowOutOfOrderMetadataProperties = true,
+        NumberHandling = JsonNumberHandling.AllowReadingFromString,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull)]
+    [JsonSerializable(typeof(CreateSessionRequest))]
+    [JsonSerializable(typeof(CreateSessionResponse))]
+    [JsonSerializable(typeof(CustomAgentConfig))]
+    [JsonSerializable(typeof(DeleteSessionRequest))]
+    [JsonSerializable(typeof(DeleteSessionResponse))]
+    [JsonSerializable(typeof(GetLastSessionIdResponse))]
+    [JsonSerializable(typeof(ListSessionsResponse))]
+    [JsonSerializable(typeof(PermissionRequestResponse))]
+    [JsonSerializable(typeof(PermissionRequestResult))]
+    [JsonSerializable(typeof(ProviderConfig))]
+    [JsonSerializable(typeof(ResumeSessionRequest))]
+    [JsonSerializable(typeof(ResumeSessionResponse))]
+    [JsonSerializable(typeof(SessionMetadata))]
+    [JsonSerializable(typeof(SystemMessageConfig))]
+    [JsonSerializable(typeof(ToolCallResponse))]
+    [JsonSerializable(typeof(ToolDefinition))]
+    [JsonSerializable(typeof(ToolResultAIContent))]
+    [JsonSerializable(typeof(ToolResultObject))]
+    internal partial class ClientJsonContext : JsonSerializerContext;
 }
 
 // Must inherit from AIContent as a signal to MEAI to avoid JSON-serializing the