[dds] Support custom requests in DAP and verify DDS is available

Change-Id: I41be607668feaab30ae10b4fe725ad3f89e4a8ba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/203861
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dds/lib/src/dap/adapters/dart.dart

@@ -12,6 +12,7 @@ import '../base_debug_adapter.dart';
 import '../exceptions.dart';
 import '../isolate_manager.dart';
 import '../logging.dart';
+import '../protocol_common.dart';
 import '../protocol_converter.dart';
 import '../protocol_generated.dart';
 import '../protocol_stream.dart';
@@ -253,6 +254,39 @@ abstract class DartDebugAdapter<T extends DartLaunchRequestArguments>
     sendResponse(ContinueResponseBody(allThreadsContinued: false));
   }
 
+  /// [customRequest] handles any messages that do not match standard messages
+  /// in the spec.
+  ///
+  /// This is used to allow a client/DA to have custom methods outside of the
+  /// spec. It is up to the client/DA to negotiate which custom messages are
+  /// allowed.
+  ///
+  /// Implementations of this method must call super for any requests they are
+  /// not handling. The base implementation will reject the request as unknown.
+  ///
+  /// Custom message starting with _ are considered internal and are liable to
+  /// change without warning.
+  @override
+  Future<void> customRequest(
+    Request request,
+    RawRequestArguments? args,
+    void Function(Object?) sendResponse,
+  ) async {
+    switch (request.command) {
+
+      /// Used by tests to validate available protocols (eg. DDS). There may be
+      /// value in making this available to clients in future, but for now it's
+      /// internal.
+      case '_getSupportedProtocols':
+        final protocols = await vmService?.getSupportedProtocols();
+        sendResponse(protocols?.toJson());
+        break;
+
+      default:
+        await super.customRequest(request, args, sendResponse);
+    }
+  }
+
   /// Overridden by sub-classes to perform any additional setup after the VM
   /// Service is connected.
   Future<void> debuggerConnected(vm.VM vmInfo);

pkg/dds/lib/src/dap/base_debug_adapter.dart

@@ -4,6 +4,8 @@
 
 import 'dart:async';
 
+import 'package:meta/meta.dart';
+
 import 'exceptions.dart';
 import 'logging.dart';
 import 'protocol_common.dart';
@@ -59,6 +61,22 @@ abstract class BaseDebugAdapter<TLaunchArgs extends LaunchRequestArguments> {
     void Function(ContinueResponseBody) sendResponse,
   );
 
+  @mustCallSuper
+  Future<void> customRequest(
+    Request request,
+    RawRequestArguments? args,
+    void Function(Object?) sendResponse,
+  ) async {
+    final response = Response(
+      success: false,
+      requestSeq: request.seq,
+      seq: _sequence++,
+      command: request.command,
+      message: 'Unknown command: ${request.command}',
+    );
+    sendResponse(response);
+  }
+
   Future<void> disconnectRequest(
     Request request,
     DisconnectArguments? args,
@@ -278,8 +296,11 @@ abstract class BaseDebugAdapter<TLaunchArgs extends LaunchRequestArguments> {
         StepInArguments.fromJson,
       );
     } else if (request.command == 'stepOut') {
-      handle(request, _withVoidResponse(stepOutRequest),
-          StepOutArguments.fromJson);
+      handle(
+        request,
+        _withVoidResponse(stepOutRequest),
+        StepOutArguments.fromJson,
+      );
     } else if (request.command == 'stackTrace') {
       handle(request, stackTraceRequest, StackTraceArguments.fromJson);
     } else if (request.command == 'scopes') {
@@ -289,14 +310,11 @@ abstract class BaseDebugAdapter<TLaunchArgs extends LaunchRequestArguments> {
     } else if (request.command == 'evaluate') {
       handle(request, evaluateRequest, EvaluateArguments.fromJson);
     } else {
-      final response = Response(
-        success: false,
-        requestSeq: request.seq,
-        seq: _sequence++,
-        command: request.command,
-        message: 'Unknown command: ${request.command}',
+      handle(
+        request,
+        customRequest,
+        _allowNullArg(RawRequestArguments.fromJson),
       );
-      _channel.sendResponse(response);
     }
   }
 

pkg/dds/lib/src/dap/protocol_common.dart

@@ -8,6 +8,19 @@ abstract class EventBody {
   static bool canParse(Object? obj) => obj is Map<String, Object?>?;
 }
 
+/// A generic arguments class that just supplies the arguments map directly.
+///
+/// Used to support custom requests that may be provided by other implementing
+/// adapters that are not known at compile time by DDS/base DAP.
+class RawRequestArguments extends RequestArguments {
+  final Map<String, Object?> args;
+
+  RawRequestArguments.fromMap(this.args);
+
+  static RawRequestArguments fromJson(Map<String, Object?> obj) =>
+      RawRequestArguments.fromMap(obj);
+}
+
 /// A base class for (spec-generated) classes that represent the `arguments` of
 /// a request.
 abstract class RequestArguments {

pkg/dds/test/dap/integration/debug_test.dart

@@ -2,8 +2,11 @@
 // 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 'package:collection/collection.dart';
 import 'package:test/test.dart';
+import 'package:vm_service/vm_service.dart';
 
+import 'test_client.dart';
 import 'test_support.dart';
 
 main() {
@@ -42,6 +45,30 @@ void main(List<String> args) async {
           'Exited.',
         ]);
       });
+
+      test('connects with DDS', () async {
+        final client = dap.client;
+        final testFile = dap.createTestFile(r'''
+void main(List<String> args) async {
+  print('Hello!'); // BREAKPOINT
+}
+    ''');
+        final breakpointLine = lineWith(testFile, '// BREAKPOINT');
+
+        await client.hitBreakpoint(testFile, breakpointLine);
+        final response = await client.custom(
+          '_getSupportedProtocols',
+          null,
+        );
+
+        // For convenience, use the ProtocolList to deserialise the custom
+        // response to check if included DDS.
+        final protocolList =
+            ProtocolList.parse(response.body as Map<String, Object?>?);
+        final ddsProtocol = protocolList?.protocols
+            ?.singleWhereOrNull((protocol) => protocol.protocolName == "DDS");
+        expect(ddsProtocol, isNot(isNull));
+      });
       // These tests can be slow due to starting up the external server process.
     }, timeout: Timeout.none);
   });

pkg/dds/test/dap/integration/test_client.dart

@@ -77,6 +77,11 @@ class DapTestClient {
   Future<Response> continue_(int threadId) =>
       sendRequest(ContinueArguments(threadId: threadId));
 
+  /// Sends a custom request to the server and waits for a response.
+  Future<Response> custom(String name, Object? args) async {
+    return sendRequest(args, overrideCommand: name);
+  }
+
   Future<Response> disconnect() => sendRequest(DisconnectArguments());
 
   /// Sends an evaluate request for the given [expression], optionally for a