Add flag to not send request in BTServiceNode

nav2_behavior_tree/include/nav2_behavior_tree/bt_action_node.hpp

@@ -196,9 +196,11 @@ class BtActionNode : public BT::ActionNodeBase
       // user defined callback, may modify "should_send_goal_".
       on_tick();
 
-      if (should_send_goal_) {
-        send_new_goal();
+      if(!should_send_goal_){
+        return BT::NodeStatus::FAILURE;
       }
+
+      send_new_goal();      
     }
 
     try {

nav2_behavior_tree/include/nav2_behavior_tree/bt_service_node.hpp

@@ -48,7 +48,7 @@ class BtServiceNode : public BT::ActionNodeBase
     const BT::NodeConfiguration & conf,
     const std::string & service_name = "")
   : BT::ActionNodeBase(service_node_name, conf), service_name_(service_name), service_node_name_(
-      service_node_name)
+      service_node_name), should_send_request_(true)
   {
     node_ = config().blackboard->template get<rclcpp::Node::SharedPtr>("node");
     callback_group_ = node_->create_callback_group(
@@ -131,10 +131,20 @@ class BtServiceNode : public BT::ActionNodeBase
   BT::NodeStatus tick() override
   {
     if (!request_sent_) {
+      // reset the flag to send the request or not, allowing the user the option to set it in on_tick
+      should_send_request_ = true;
+
+      // user defined callback, may modify "should_send_request_".
       on_tick();
+
+      if(!should_send_request_){
+        return BT::NodeStatus::FAILURE;
+      }
+
       future_result_ = service_client_->async_send_request(request_).share();
       sent_time_ = node_->now();
       request_sent_ = true;
+
     }
     return check_future();
   }
@@ -243,6 +253,9 @@ class BtServiceNode : public BT::ActionNodeBase
   std::shared_future<typename ServiceT::Response::SharedPtr> future_result_;
   bool request_sent_{false};
   rclcpp::Time sent_time_;
+
+  // Can be set in on_tick or on_wait_for_result to indicate if a request should be sent.
+  bool should_send_request_;
 };
 
 }  // namespace nav2_behavior_tree