[lldb-dap] Updating RequestHandler to encode/decode arguments and response.

This is a work in progress refactor to add explicit types instead of
generic 'llvm::json::Value' types to the DAP protocol.

This updates RequestHandler to have take the type of the arguments and
response body for serialization for requests.

The 'source' request is updated to show how the new flow works.

Author: ashgti

lldb/tools/lldb-dap/DAP.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "DAP.h"
+#include "Handler/RequestHandler.h"
 #include "Handler/ResponseHandler.h"
 #include "JSONUtils.h"
 #include "LLDBUtils.h"
@@ -24,6 +25,7 @@
 #include "lldb/lldb-defines.h"
 #include "lldb/lldb-enumerations.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
@@ -39,6 +41,7 @@
 #include <fstream>
 #include <memory>
 #include <mutex>
+#include <string>
 #include <utility>
 
 #if defined(_WIN32)
@@ -684,59 +687,61 @@ void DAP::SetTarget(const lldb::SBTarget target) {
 }
 
 bool DAP::HandleObject(const protocol::Message &M) {
-  llvm::json::Value v = toJSON(M);
-  llvm::json::Object object = *v.getAsObject();
-  const auto packet_type = GetString(object, "type");
-  if (packet_type == "request") {
-    const auto command = GetString(object, "command");
-
-    auto new_handler_pos = request_handlers.find(command);
+  if (const auto *req = std::get_if<protocol::Request>(&M)) {
+    auto new_handler_pos = request_handlers.find(req->command);
     if (new_handler_pos != request_handlers.end()) {
-      (*new_handler_pos->second)(object);
+      (*new_handler_pos->second)(*req);
       return true; // Success
     }
 
     if (log)
-      *log << "error: unhandled command \"" << command.data() << "\""
+      *log << "error: unhandled command \"" << req->command << "\""
            << std::endl;
     return false; // Fail
   }
 
-  if (packet_type == "response") {
-    auto id = GetInteger<int64_t>(object, "request_seq").value_or(0);
-
+  if (const auto *resp = std::get_if<protocol::Response>(&M)) {
     std::unique_ptr<ResponseHandler> response_handler;
     {
       std::lock_guard<std::mutex> locker(call_mutex);
-      auto inflight = inflight_reverse_requests.find(id);
+      auto inflight = inflight_reverse_requests.find(resp->request_seq);
       if (inflight != inflight_reverse_requests.end()) {
         response_handler = std::move(inflight->second);
         inflight_reverse_requests.erase(inflight);
       }
     }
 
     if (!response_handler)
-      response_handler = std::make_unique<UnknownResponseHandler>("", id);
+      response_handler =
+          std::make_unique<UnknownResponseHandler>("", resp->request_seq);
 
     // Result should be given, use null if not.
-    if (GetBoolean(object, "success").value_or(false)) {
-      llvm::json::Value Result = nullptr;
-      if (auto *B = object.get("body")) {
-        Result = std::move(*B);
-      }
-      (*response_handler)(Result);
+    if (resp->success) {
+      (*response_handler)(resp->rawBody);
     } else {
-      llvm::StringRef message = GetString(object, "message");
-      if (message.empty()) {
-        message = "Unknown error, response failed";
+      std::string message = "Unknown error, response failed";
+      if (resp->message) {
+        message = std::visit(
+            llvm::makeVisitor(
+                [](const std::string &message) -> std::string {
+                  return message;
+                },
+                [](const protocol::Response::Message &message) -> std::string {
+                  return "hi";
+                }),
+            *resp->message);
       }
+
       (*response_handler)(llvm::createStringError(
           std::error_code(-1, std::generic_category()), message));
     }
 
     return true;
   }
 
+  if (log)
+    *log << "Unsupported protocol message" << std::endl;
+
   return false;
 }
 

lldb/tools/lldb-dap/DAP.h

@@ -12,8 +12,6 @@
 #include "DAPForward.h"
 #include "ExceptionBreakpoint.h"
 #include "FunctionBreakpoint.h"
-#include "Handler/RequestHandler.h"
-#include "Handler/ResponseHandler.h"
 #include "InstructionBreakpoint.h"
 #include "OutputRedirector.h"
 #include "ProgressEvent.h"
@@ -188,7 +186,7 @@ struct DAP {
   // the old process here so we can detect this case and keep running.
   lldb::pid_t restarting_process_id;
   bool configuration_done_sent;
-  llvm::StringMap<std::unique_ptr<RequestHandler>> request_handlers;
+  llvm::StringMap<std::unique_ptr<BaseRequestHandler>> request_handlers;
   bool waiting_for_run_in_terminal;
   ProgressEventReporter progress_event_reporter;
   // Keep track of the last stop thread index IDs as threads won't go away

lldb/tools/lldb-dap/DAPForward.h

@@ -19,6 +19,8 @@ struct SourceBreakpoint;
 struct Watchpoint;
 struct InstructionBreakpoint;
 struct DAP;
+class BaseRequestHandler;
+class ResponseHandler;
 } // namespace lldb_dap
 
 namespace lldb {

lldb/tools/lldb-dap/Handler/RequestHandler.cpp

@@ -6,8 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "RequestHandler.h"
+#include "Handler/RequestHandler.h"
 #include "DAP.h"
+#include "Handler/ResponseHandler.h"
 #include "JSONUtils.h"
 #include "LLDBUtils.h"
 #include "RunInTerminal.h"
@@ -45,7 +46,7 @@ static uint32_t SetLaunchFlag(uint32_t flags, const llvm::json::Object *obj,
 
 // Both attach and launch take either a sourcePath or a sourceMap
 // argument (or neither), from which we need to set the target.source-map.
-void RequestHandler::SetSourceMapFromArguments(
+void BaseRequestHandler::SetSourceMapFromArguments(
     const llvm::json::Object &arguments) const {
   const char *sourceMapHelp =
       "source must be be an array of two-element arrays, "
@@ -159,7 +160,7 @@ static llvm::Error RunInTerminal(DAP &dap,
 }
 
 lldb::SBError
-RequestHandler::LaunchProcess(const llvm::json::Object &request) const {
+BaseRequestHandler::LaunchProcess(const llvm::json::Object &request) const {
   lldb::SBError error;
   const auto *arguments = request.getObject("arguments");
   auto launchCommands = GetStrings(arguments, "launchCommands");
@@ -228,13 +229,13 @@ RequestHandler::LaunchProcess(const llvm::json::Object &request) const {
   return error;
 }
 
-void RequestHandler::PrintWelcomeMessage() const {
+void BaseRequestHandler::PrintWelcomeMessage() const {
 #ifdef LLDB_DAP_WELCOME_MESSAGE
   dap.SendOutput(OutputType::Console, LLDB_DAP_WELCOME_MESSAGE);
 #endif
 }
 
-bool RequestHandler::HasInstructionGranularity(
+bool BaseRequestHandler::HasInstructionGranularity(
     const llvm::json::Object &arguments) const {
   if (std::optional<llvm::StringRef> value = arguments.getString("granularity"))
     return value == "instruction";