[lldb][lldb-dap] Basic implementation of a deferred request.

almost one to one except not deferring breakpoints.

Author: da-viper

lldb/tools/lldb-dap/DAP.cpp

@@ -726,7 +726,7 @@ void DAP::SetTarget(const lldb::SBTarget target) {
   }
 }
 
-bool DAP::HandleObject(const Message &M) {
+bool DAP::HandleObject(const Message &M, bool &defer) {
   TelemetryDispatcher dispatcher(&debugger);
   dispatcher.Set("client_name", transport.GetClientName().str());
   if (const auto *req = std::get_if<Request>(&M)) {
@@ -748,7 +748,7 @@ bool DAP::HandleObject(const Message &M) {
     dispatcher.Set("client_data",
                    llvm::Twine("request_command:", req->command).str());
     if (handler_pos != request_handlers.end()) {
-      handler_pos->second->Run(*req);
+      defer = handler_pos->second->Run(*req);
       return true; // Success
     }
 
@@ -918,17 +918,11 @@ llvm::Error DAP::Loop() {
 
           // The launch sequence is special and we need to carefully handle
           // packets in the right order. Until we've handled configurationDone,
-          bool add_to_pending_queue = false;
-
           if (const protocol::Request *req =
                   std::get_if<protocol::Request>(&*next)) {
             llvm::StringRef command = req->command;
             if (command == "disconnect")
               disconnecting = true;
-            if (!configuration_done)
-              add_to_pending_queue =
-                  command != "initialize" && command != "configurationDone" &&
-                  command != "disconnect" && !command.ends_with("Breakpoints");
           }
 
           const std::optional<CancelArguments> cancel_args =
@@ -956,8 +950,7 @@ llvm::Error DAP::Loop() {
 
           {
             std::lock_guard<std::mutex> guard(m_queue_mutex);
-            auto &queue = add_to_pending_queue ? m_pending_queue : m_queue;
-            queue.push_back(std::move(*next));
+            m_queue.push_back(std::move(*next));
           }
           m_queue_cv.notify_one();
         }
@@ -984,9 +977,13 @@ llvm::Error DAP::Loop() {
     // Unlock while we're processing the event.
     lock.unlock();
 
-    if (!HandleObject(next))
+    bool defer_message = false;
+    if (!HandleObject(next, defer_message))
       return llvm::createStringError(llvm::inconvertibleErrorCode(),
                                      "unhandled packet");
+    if (defer_message) {
+      m_pending_queue.push_back(next);
+    }
   }
 
   return ToError(queue_reader.get());

lldb/tools/lldb-dap/DAP.h

@@ -339,7 +339,7 @@ struct DAP {
   /// listeing for its breakpoint events.
   void SetTarget(const lldb::SBTarget target);
 
-  bool HandleObject(const protocol::Message &M);
+  bool HandleObject(const protocol::Message &M, bool &defer);
 
   /// Disconnect the DAP session.
   llvm::Error Disconnect();

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

@@ -160,4 +160,8 @@ void AttachRequestHandler::PostRun() const {
     dap.target.GetProcess().Continue();
 }
 
+bool AttachRequestHandler::DeferRequest() const {
+  return !dap.configuration_done;
+}
+
 } // namespace lldb_dap

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

@@ -88,4 +88,8 @@ void LaunchRequestHandler::PostRun() const {
     dap.target.GetProcess().Continue();
 }
 
+bool LaunchRequestHandler::DeferRequest() const {
+  return !dap.configuration_done;
+}
+
 } // namespace lldb_dap

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

@@ -126,7 +126,7 @@ RunInTerminal(DAP &dap, const protocol::LaunchRequestArguments &arguments) {
                                  error.GetCString());
 }
 
-void BaseRequestHandler::Run(const Request &request) {
+bool BaseRequestHandler::Run(const Request &request) {
   // If this request was cancelled, send a cancelled response.
   if (dap.IsCancelled(request)) {
     Response cancelled{/*request_seq=*/request.seq,
@@ -135,12 +135,15 @@ void BaseRequestHandler::Run(const Request &request) {
                        /*message=*/eResponseMessageCancelled,
                        /*body=*/std::nullopt};
     dap.Send(cancelled);
-    return;
+    return false;
   }
 
   lldb::SBMutex lock = dap.GetAPIMutex();
   std::lock_guard<lldb::SBMutex> guard(lock);
 
+  if (DeferRequest()) {
+    return true;
+  }
   // FIXME: After all the requests have migrated from LegacyRequestHandler >
   // RequestHandler<> we should be able to move this into
   // RequestHandler<>::operator().
@@ -149,6 +152,7 @@ void BaseRequestHandler::Run(const Request &request) {
   // FIXME: After all the requests have migrated from LegacyRequestHandler >
   // RequestHandler<> we should be able to check `debugger.InterruptRequest` and
   // mark the response as cancelled.
+  return false;
 }
 
 llvm::Error BaseRequestHandler::LaunchProcess(

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

@@ -46,7 +46,11 @@ class BaseRequestHandler {
 
   virtual ~BaseRequestHandler() = default;
 
-  void Run(const protocol::Request &);
+  /// Return `true` if the request should be deferred.
+  [[nodiscard]]
+  bool Run(const protocol::Request &);
+
+  virtual bool DeferRequest() const { return false; };
 
   virtual void operator()(const protocol::Request &request) const = 0;
 
@@ -203,6 +207,7 @@ class AttachRequestHandler
   static llvm::StringLiteral GetCommand() { return "attach"; }
   llvm::Error Run(const protocol::AttachRequestArguments &args) const override;
   void PostRun() const override;
+  bool DeferRequest() const override;
 };
 
 class BreakpointLocationsRequestHandler
@@ -302,6 +307,7 @@ class LaunchRequestHandler
   llvm::Error
   Run(const protocol::LaunchRequestArguments &arguments) const override;
   void PostRun() const override;
+  bool DeferRequest() const override;
 };
 
 class RestartRequestHandler : public LegacyRequestHandler {