I have a idea to improve it, when we want to use Subscriber for LifecycleNode, we should define

message_filters::Subscriber<sensor_msgs::msg::LaserScan,rclcpp_lifecycle::LifecycleNode>  sub_;
// it looks like too long

we can adapt Subscriber class to be used with LifecycleNode and Node by using rclcpp::node_interfaces::NodeBaseInterface::SharedPtr , a example in tf2_ros/transform_listener.h , like this:

template<class NodeT>
Subscriber(NodeT &node, ...){
   node_base_interface_ = node->get_node_base_interface();
}

then, we can create subscription by using node_base_interface_ .

@mjcarroll can you rerun CI?

@tfoote @Karsten1987 can you re-review and/or approve this PR? I believe it meets all of the requirements Karsten wanted. It's something we're trying to use in Nav2 in order to remove excess rclcpp::Node's from our servers as part of @gezp's summer project with me. A sync to rolling after merging would be massive beneficial as well if possible 😄 (but I won't push it if I can get only one 😉 )

This is also something we rely on quite a bit in Nav2. I'd be happy to take on a co-maintainership role on this project as well if that would help for future inquiries.

@ros-pull-request-builder retest this please

Thank you both for the help! Does this need a second maintainer review to be merged? Else, I've reviewed independently and am satisfied with this solution.

@mjcarroll can we get a sync with rolling?

@SteveMacenski ros/rosdistro#30350

Thank you!