!fix(Client): Do not hold goal_handle ptr if result cb is set.

The capture of the lambda held an copy of the shared_ptr to the
goal handle. This lead to the behavior that the goal callbacks
would be called, even though the user dropped the handle.

Note, this will break the current tutorial, as it restores the documented
behavior that a goal will be invalidated as soon as one drops the handle.

Signed-off-by: Janosch Machowinski <[email protected]>

Author: Janosch Machowinski

rclcpp_action/include/rclcpp_action/client.hpp

@@ -726,23 +726,40 @@ class Client : public ClientBase, public std::enable_shared_from_this<Client<Act
     }
     using GoalResultRequest = typename ActionT::Impl::GetResultService::Request;
     auto goal_result_request = std::make_shared<GoalResultRequest>();
+    const GoalUUID goal_id = goal_handle->get_goal_id();
     goal_result_request->goal_id.uuid = goal_handle->get_goal_id();
     try {
       this->send_result_request(
         std::static_pointer_cast<void>(goal_result_request),
-        [goal_handle, this](std::shared_ptr<void> response) mutable
+        [goal_id, this](std::shared_ptr<void> response) mutable
         {
+          std::lock_guard<std::mutex> lock(goal_handles_mutex_);
+          if (goal_handles_.count(goal_id) == 0) {
+            RCLCPP_DEBUG(
+              this->get_logger(),
+              "Received result for unknown goal. Ignoring...");
+            return;
+          }
+          typename GoalHandle::SharedPtr goal_handle_ = goal_handles_[goal_id].lock();
+          // Forget about the goal if there are no more user references
+          if (!goal_handle_) {
+            RCLCPP_DEBUG(
+              this->get_logger(),
+              "Dropping weak reference to goal handle during result callback");
+            goal_handles_.erase(goal_id);
+            return;
+          }
+
           // Wrap the response in a struct with the fields a user cares about
           WrappedResult wrapped_result;
           using GoalResultResponse = typename ActionT::Impl::GetResultService::Response;
           auto result_response = std::static_pointer_cast<GoalResultResponse>(response);
           wrapped_result.result = std::make_shared<typename ActionT::Result>();
           *wrapped_result.result = result_response->result;
-          wrapped_result.goal_id = goal_handle->get_goal_id();
+          wrapped_result.goal_id = goal_id;
           wrapped_result.code = static_cast<ResultCode>(result_response->status);
-          goal_handle->set_result(wrapped_result);
-          std::lock_guard<std::mutex> lock(goal_handles_mutex_);
-          goal_handles_.erase(goal_handle->get_goal_id());
+          goal_handle_->set_result(wrapped_result);
+          goal_handles_.erase(goal_id);
         });
     } catch (rclcpp::exceptions::RCLError & ex) {
       // This will cause an exception when the user tries to access the result