[ Service ] Fix dart:developer service extensions, add getSupportedProtocols

Brings package:vm_service test suite pass rate up to ~93%

Change-Id: I108a24e1acf37eb69c9de25a2f7334eb4c56dbe6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/487600
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dart_runtime_service_vm/lib/dart_runtime_service_vm.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:isolate';
@@ -13,6 +14,7 @@ import 'package:json_rpc_2/json_rpc_2.dart' as json_rpc;
 import 'package:logging/logging.dart';
 import 'package:stream_channel/stream_channel.dart';
 
+import 'src/dart_runtime_service_vm_rpcs.dart';
 import 'src/native_bindings.dart';
 import 'src/vm_expression_evaluator.dart';
 import 'src/vm_isolate_manager.dart';
@@ -73,6 +75,20 @@ class DartRuntimeServiceVMBackend
   @override
   late final VmExpressionEvaluator expressionEvaluator;
 
+  final _vmServiceRpcs = DartRuntimeServiceVmRpcs();
+
+  @override
+  UnmodifiableListView<ServiceRpcHandler> get rpcs =>
+      UnmodifiableListView(_vmServiceRpcs.rpcs);
+
+  @override
+  UnmodifiableListView<RpcHandlerWithParameters>
+  get fallbacks => UnmodifiableListView([
+    // If the registered Dart RPC handlers can't handle a request, forward it
+    // it to the native VM service implementation for processing.
+    sendToRuntime,
+  ]);
+
   @override
   Future<void> initialize() async {
     _logger.info('Initializing...');
@@ -148,18 +164,6 @@ class DartRuntimeServiceVMBackend
     _nativeBindings.streamCancel(streamId: streamId);
   }
 
-  @override
-  void registerRpcs(json_rpc.Peer clientPeer) {
-    // The VM service handles its service requests in service.cc.
-  }
-
-  @override
-  void registerFallbacks(json_rpc.Peer clientPeer) {
-    // If the registered Dart RPC handlers can't handle a request, forward it
-    // it to the native VM service implementation for processing.
-    clientPeer.registerFallback(sendToRuntime);
-  }
-
   /// Sends service requests to the Dart VM runtime for processing.
   Future<RpcResponse> sendToRuntime(json_rpc.Parameters request) async {
     final method = request.method;

pkg/dart_runtime_service_vm/lib/src/dart_runtime_service_vm_rpcs.dart

@@ -0,0 +1,46 @@
+// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:collection';
+
+import 'package:dart_runtime_service/dart_runtime_service.dart';
+import 'package:logging/logging.dart';
+import 'package:vm_service/vm_service.dart';
+
+import 'native_bindings.dart';
+
+/// Implementations of RPCs specific to the VM service that are not handled
+/// in runtime/vm/service.cc.
+final class DartRuntimeServiceVmRpcs {
+  final _logger = Logger('$DartRuntimeServiceVmRpcs');
+  final _nativeBindings = NativeBindings();
+
+  late final rpcs = UnmodifiableListView<ServiceRpcHandler>([
+    ('getSupportedProtocols', getSupportedProtocols),
+  ]);
+
+  /// Returns the list of protocols implemented by the service.
+  ///
+  /// VM service middleware like DDS should intercept this RPC and add their
+  /// own information to the response.
+  Future<RpcResponse> getSupportedProtocols() async {
+    final version = Version.parse(
+      await _nativeBindings.sendToVM(method: 'getVersion', params: const {}),
+    );
+    if (version == null) {
+      _logger.warning('Unable to retrieve version for getSupportedProtocols.');
+      RpcException.internalError.throwException();
+    }
+
+    return ProtocolList(
+      protocols: [
+        Protocol(
+          protocolName: 'VM Service',
+          major: version.major,
+          minor: version.minor,
+        ),
+      ],
+    ).toJson();
+  }
+}

pkg/dart_runtime_service_vm/lib/src/native_bindings.dart

@@ -133,10 +133,16 @@ class NativeBindings {
     const kData = 'data';
 
     final Object? converted;
-    if (value case [final Uint8List utf8String]) {
+    if (value case final String string) {
+      converted = json.decode(string);
+    } else if (value case [final Uint8List utf8String]) {
       converted = jsonUtf8Decoder.decode(utf8String);
     } else {
-      RpcException.internalError.throwException();
+      RpcException.internalError.throwException(
+        data: {
+          'details': 'Unknown response type (${value.runtimeType}: $value)',
+        },
+      );
     }
     if (converted case {kResult: final Map<String, Object?> result}) {
       return result;