Shader Generation problem with `<postition>` and `interfacename`

[ld-kerley]

I suspect I have found a shader generation bug. It appears that using a <position> inside a nodegraph, and exposing the space parameter via the interface name mechanism appears to not generate valid shader code, either in MSL or OSL.

Using the <position> node alone appears to work.

<?xml version="1.0"?>
<materialx version="1.38" colorspace="lin_rec709">

  <position name="myPos" type="vector3">
    <input name="space" type="string" value="object"/>
  </position>

  <convert name="conv" type="color3">
    <input name="in" type="vector3" nodename="myPos"/>
  </convert>
  <surface_unlit name="Srf" type="surfaceshader">
    <input name="emission_color" type="color3" nodename="conv" />
  </surface_unlit>
  <surfacematerial name="Mtl" type="material">
    <input name="surfaceshader" type="surfaceshader" nodename="Srf" />
  </surfacematerial>

</materialx>

But the following doesn't work

<?xml version="1.0"?>
<materialx version="1.38" colorspace="lin_rec709">

  <nodedef name="ND_positionwrapper" node="positionwrapper">
    <input name="wrap_space" type="string" value="object" enum="model, object, world" uniform="true"/>
    <output name="out" type="vector3"/>
  </nodedef>

  <nodegraph name="NG_positionwrapper" nodedef="ND_positionwrapper">
    <position name="myPos" type="vector3">
      <input name="space" type="string" interfacename="wrap_space"/>
    </position>
    <output name="out" type="vector3" nodename="myPos"/>
  </nodegraph>


  <positionwrapper name="myPosWrapper" type="vector3">
    <input name="wrap_space" type="string" value="object"/>
  </positionwrapper>

  <convert name="conv" type="color3">
    <input name="in" type="vector3" nodename="myPosWrapper"/>
  </convert>
  <surface_unlit name="Srf" type="surfaceshader">
    <input name="emission_color" type="color3" nodename="conv" />
  </surface_unlit>
  <surfacematerial name="Mtl" type="material">
    <input name="surfaceshader" type="surfaceshader" nodename="Srf" />
  </surfacematerial>

</materialx>

It's possible I'm holding it wrong. If I am I'd love to be schooled by someone.

This is obviously a toy example, but I'm trying to build some custom node definitions that are using <position> internally, exposing the space parameter back to the user.

[ld-kerley]

I think this may be related to using interfacename with an input that has an enumeration defined. I may have a fix, but would appreciate any insight if anyone else has hit this before.

[ld-kerley]

This was fix in #2423