Validation incorrectly categorizes top level inputs connected to graphs as invalid

[kwokcb]

Issue

Validation considers a top level input conneted to an interface input on a nodegraph as invalid even though this
should be valid and is accepted by code generation.

Test data

<?xml version="1.0"?>
<materialx version="1.39" colorspace="lin_rec709">
  <input name="input_color4" type="color3" value="0,0,0" xpos="10.094203" ypos="0.439655" />
  <input name="input_float1" type="float" value="0" xpos="9.862319" ypos="1.818966" />
  <nodegraph name="custom_graph_1">
    <input name="matrixIn" type="matrix33" value="1,0.2,0.2,0,1,0,0,0,1" />
    <input name="floatIn" type="float" interfacename="input_float1" />
    <input name="color3In" type="color3" interfacename="input_color4" />
    <output name="output_matrix34" type="matrix33" nodename="dot_matrix34" />
    <output name="floatOut" type="float" nodename="dot_float1" />
    <output name="color3Out" type="color3" nodename="dot_color4" />
    <output name="color3Gamma22Out" type="color3" nodename="colorcorrect_color4" />
    <dot name="dot_float1" type="float">
      <input name="in" type="float" interfacename="floatIn" />
      <input name="note" type="string" value="" />
    </dot>
    <dot name="dot_matrix34" type="matrix33">
      <input name="in" type="matrix33" interfacename="matrixIn" />
      <input name="note" type="string" value="" />
    </dot>
    <dot name="dot_color4" type="color3">
      <input name="in" type="color3" interfacename="color3In" />
      <input name="note" type="string" value="" />
    </dot>
    <colorcorrect name="colorcorrect_color4" type="color3">
      <input name="in" type="color3" interfacename="color3In" />
      <input name="hue" type="float" value="0" />
      <input name="saturation" type="float" value="1" />
      <input name="gamma" type="float" value="2.2" />
      <input name="lift" type="float" value="0" />
      <input name="gain" type="float" value="1" />
      <input name="contrast" type="float" value="1" />
      <input name="contrastpivot" type="float" value="0.5" />
      <input name="exposure" type="float" value="0" />
    </colorcorrect>
  </nodegraph>
  <nodegraph name="ramp_graph">
    <input name="input_vector3" type="vector2" value="0,0" />
    <input name="Left_color" type="color3" value="0, 0, 0" />
    <input name="Right_color" type="color3" output="color3Gamma22Out" nodegraph="custom_graph_1" />
    <output name="out" type="color3" nodename="ramplr_color4" />
    <ramplr name="ramplr_color4" type="color3">
      <input name="valuel" type="color3" interfacename="Left_color" />
      <input name="valuer" type="color3" interfacename="Right_color" />
      <input name="texcoord" type="vector2" interfacename="input_vector3" />
    </ramplr>
  </nodegraph>
  <surface_unlit name="surface_unlit" type="surfaceshader" xpos="20.028986" ypos="0.784483">
    <input name="emission_color" type="color3" output="out" nodegraph="ramp_graph" />
  </surface_unlit>
  <surfacematerial name="surfacematerial" type="material" xpos="22.695652" ypos="0.732759">
    <input name="surfaceshader" type="surfaceshader" nodename="surface_unlit" />
  </surfacematerial>
</materialx>

These interface connections are considered invalid.

  <input name="floatIn" type="float" interfacename="input_float1" />
   <input name="color3In" type="color3" interfacename="input_color4" />

with these errors:

Interface name not found in referenced declaration: <input name="floatIn" type="float" interfacename="input_float1">
Interface name not found in referenced declaration: <input name="color3In" type="color3" interfacename="input_color4">

Code gen and rendering see fine if you ignore the validation error. This is an ESSL render

Proposed Fix

The issue appears to be that when trying to find a parent graph element, the top level document (which is a graph) is
precluded here:

ConstNodeGraphPtr nodeGraph = getAncestorOfType<NodeGraph>();

precludes checking for the document Seems like the fix is to check for GraphElement and not NodeGraph.