Type conversion problem with subtree

[lvanroye]

I am trying to pass a double deque through a subtree.

 <root BTCPP_format="4" >

     <TreeNodesModel>
       <SubTree ID="PrintNumberLoop">
         <input_port name="queue_values"/>
       </SubTree>
     </TreeNodesModel>

     <BehaviorTree ID="PrintNumberLoop">
        <LoopDouble queue="{queue_values}" value="{number}">
            <PrintNumber value="{number}" />
        </LoopDouble>
     </BehaviorTree>

     <BehaviorTree ID="TreeA">
        <Sequence>
            <SubTree ID="PrintNumberLoop" queue_values="1;2;3" />
        </Sequence>
     </BehaviorTree>
 </root>
 )"

However when I do this I get the error

terminate called after throwing an instance of 'std::runtime_error'
  what():  [Any::convert]: no known safe conversion between [std::string] and [std::shared_ptr<std::deque<double, std::allocator<double> > >]
[1]    2397806 IOT instruction (core dumped)  ./t18_waypoints

The problem can be reproduced by this piece of code

#include "behaviortree_cpp/bt_factory.h"
#include "behaviortree_cpp/decorators/loop_node.h"
#include "behaviortree_cpp/loggers/bt_cout_logger.h"

#include <deque>

using namespace BT;

//--------------------------------------------------------------
class PrintNumber : public SyncActionNode
{
public:
  PrintNumber(const std::string& name, const NodeConfig& config)
    : SyncActionNode(name, config)
  {}

  NodeStatus tick() override
  {
    double value;
    if(getInput("value", value))
    {
      std::cout << "PrintNumber: " << value << "\n";
      return NodeStatus::SUCCESS;
    }
    return NodeStatus::FAILURE;
  }

  static PortsList providedPorts()
  {
    return { InputPort<double>("value") };
  }
};

// clang-format off
static const char* xml_tree = R"(
 <root BTCPP_format="4" >

     <TreeNodesModel>
       <SubTree ID="PrintNumberLoop">
         <input_port name="queue_values"/>
       </SubTree>
     </TreeNodesModel>

     <BehaviorTree ID="PrintNumberLoop">
        <LoopDouble queue="{queue_values}" value="{number}">
            <PrintNumber value="{number}" />
        </LoopDouble>
     </BehaviorTree>

     <BehaviorTree ID="TreeA">
        <Sequence>
            <SubTree ID="PrintNumberLoop" queue_values="1;2;3" />
        </Sequence>
     </BehaviorTree>
 </root>
 )";

// clang-format on

int main()
{
  BehaviorTreeFactory factory;

  factory.registerNodeType<PrintNumber>("PrintNumber");

  factory.registerBehaviorTreeFromText(xml_tree);
  auto tree = factory.createTree("TreeA");

  StdCoutLogger logger(tree);
  logger.enableTransitionToIdle(false);

  tree.tickWhileRunning();

  return 0;
}

I have a workaround with an extra component to convert an std::string input to a double deque output, however I wonder if there is a more elegant solution available.