programmatically read extras / custom properties from remote GLTF in Godot 4 gdscript

load_remote_GLTF_extras_metadata.gd

# For more sophisticated use of loading remote GLTF (with extras) use the xrfragment.org spec & xrfragment.gd script
# XRFRAGMENT.ORG is a mini-spec which standardizes 3D metadata without fileformat or platform lock-in
#
# Usage:
#
#       load("https://xrfragment.org/index.glb")
# 	var doc = GLTFDocument.new()
#	var state = GLTFState.new()
#	#state.set_handle_binary_image(GLTFState.HANDLE_BINARY_EMBED_AS_BASISU) # Fixed in new Godot version (4.3 as I see) https://github.com/godotengine/godot/blob/17e7f85c06366b427e5068c5b3e2940e27ff5f1d/scene/resources/portable_compressed_texture.cpp#L116
#	var error = doc.append_from_buffer(body, "", state)
#	if error == OK:
#		var scene = doc.generate_scene(state)		
#		metadata = _parseMetadata(state,scene)
#		traverse(scene, evalNode)
#		add_child(scene)
#   print( find_child("mygltfnode").get_meta("extras")["foo"] ) # access extra 

func _parseMetadata(state: GLTFState, scene: Node) -> Error:
	#var meta = new Dictionary()
	
	# Add metadata to materials
	var materials_json : Array = state.json.get("materials", [])
	var materials : Array[Material] = state.get_materials()
	for i in materials_json.size():
		if materials_json[i].has("extras"):
			materials[i].set_meta("extras", materials_json[i]["extras"])
		
	# Add metadata to ImporterMeshes
	var meshes_json : Array = state.json.get("meshes", [])
	var meshes : Array[GLTFMesh] = state.get_meshes()
	for i in meshes_json.size():
		if meshes_json[i].has("extras"):
			meshes[i].mesh.set_meta("extras", meshes_json[i]["extras"])	
	
	# Add metadata to nodes
	var nodes_json : Array = state.json.get("nodes", [])
	for i in nodes_json.size():
		if nodes_json[i].has("extras"):
			var name = nodes_json[i]["name"].replace(".","_")
			var node = scene.find_child(name) #state.get_scene_node(i)
			if node:
				node.set_meta( "extras", nodes_json[i]["extras"] )
			else:
				print(name+" could not be found")
	return OK