How to return an object that has a child object?

[travbid]

node version: 8.9.3
nbind version: 0.3.14
OS: Ubuntu 17.10

I can't seem to pass an object from C++ to JavaScript when that object has object members.

Here's a minimal reproducible example:

hello.cc:

#include "nbind/api.h"

// header.hpp ----------
struct foo {
  int x;
};

struct myParent {
  foo child;
  int y;
};

myParent originalFunction() {
  myParent mp;
  mp.child.x = 5;
  mp.y = 6;
  return mp;
}
// ---------------------

class foo_wrapper {
public:
  foo_wrapper(foo f) { val = f; }
  void toJS(nbind::cbOutput output) {
    output(val.x);
  }

  foo val;
};

class myParent_wrapper {
public:
  myParent_wrapper(myParent s) { val = s; }
  void toJS(nbind::cbOutput output) {
    output(foo_wrapper(val.child), val.y);
  }

  myParent val;
};

myParent_wrapper myFunc() {
  return myParent_wrapper(originalFunction());
}

#include "nbind/nbind.h"

NBIND_CLASS(foo) {}
NBIND_CLASS(myParent) {}
NBIND_CLASS(myParent_wrapper) { construct<myParent>(); }
NBIND_CLASS(foo_wrapper) { construct<foo>(); }

NBIND_GLOBAL() { function(myFunc); }

index.js:

let nbind = require('nbind')
let binding = nbind.init()
let lib = binding.lib

class classFoo {
	constructor(x) {
		this.x = x;
	}
	fromJS(output) {
		output(this.x)
	}
}

class classParent {
	constructor(a, b) {
		this.child = a;
		this.y = b;
	}
	fromJS(output) {
		output(this.child, this.b);
	}
}

binding.bind('foo_wrapper', classFoo);
binding.bind('myParent_wrapper', classParent);

console.log(lib.myFunc());

Output I expect from node ./index.js:

classParent { child: classFoo {x: 5}, y: 6 }

What I see instead:

classParent { child: foo_wrapper {}, y: 6 }

Am I doing something wrong? Any help would be appreciated.

[TanninOne]

I'm interested in this as well.
When you pass the foo_wrapper directly to output however it's toJS function is never called so you get the wrapper object in js.
I found that when you write something like output(std::vector<foo_wrapper>{ foo_wrapper(val.child) }) then it will transform the array element with toJS so you'd get an array of classFoo objects in javascript.