Feature request: generic sub nodes and ports

[mnumanuyar]

Currently to use topics in BT I wirte up a simple sub node and expose needed members as ports. This works, however after a while there are a lot of similiar code.

Is it possible to make this generic?

Also it would be nice to have generic port types for topic types. To this, to_yaml functions could be used. For example

    multi_uav_bt_nodes::Pose msg;
    msg.position.x = 10;
    msg.position.y = 10;
    msg.position.z = 10;
    EXPECT_EQ( geometry_msgs::msg::to_yaml(msg,true), "{position: {x: 10.0000, y: 10.0000, z: 10.0000}, orientation: {x: 0.00000, y: 0.00000, z: 0.00000, w: 1.00000}}" );

couldnt find how to parse it but probobly some function rosidl will work.

Also for reference my sub nodes looks like this:

using Pose = geometry_msgs::msg::Pose;

class ListenPoseAction : public BT::RosTopicSubNode<Pose>
{
public:
  ListenPoseAction(
    const std::string & name,
    const BT::NodeConfig & conf,
    const BT::RosNodeParams & params)
  : BT::RosTopicSubNode<Pose>(name, conf, params) {}

  static BT::PortsList providedPorts();

  BT::NodeStatus onTick(const typename Pose::SharedPtr & last_msg) override;

  virtual ~ListenPoseAction();
};

BT::PortsList ListenPoseAction::providedPorts()
{
  return providedBasicPorts(
    {
      BT::OutputPort<double>("X"),
      BT::OutputPort<double>("Y"),
      BT::OutputPort<double>("Z")});
}

BT::NodeStatus ListenPoseAction::onTick(const typename Pose::SharedPtr & last_msg)
{
  if (!last_msg) {
    return BT::NodeStatus::FAILURE;
  }
  setOutput("X", last_msg->position.x);
  setOutput("Y", last_msg->position.y);
  setOutput("Z", last_msg->position.z);
  return BT::NodeStatus::SUCCESS;
}

ListenPoseAction::~ListenPoseAction()
{
}

note that ony the first line of the hpp (which could be a template variable) and code related to ports (which would be the generic port) change for different ros topics

[mnumanuyar]

if not for the missing parser function and some small details this could have been a merge request 😿

[mnumanuyar]

I wonder how nav2 did it 🤔

[mnumanuyar]

I have done this a while ago (with sligthly modified dynmsgs ) However, the code is intermingled with personal stuff, and also there some problematic edge cases so i cant create a merge request.

however I wonder if this can somehow used for a better result: https://github.com/facontidavide/rosx_introspection