ID 438878 - A convert layers prompt appears when loading a project with a custom node that includes a call to the Channels attribute.

Problem summary
A convert layers prompt appears when loading a project with a custom node that includes a call to the Channels attribute.

Customer reported version
mari.4.6v3

Customer reported platform
windows10

Steps to reproduce

1) Copy any standard node from the Bundle/Simple/Procedural director, then open it to edit.

2) Add the following line to the Attributes list and save the custom node:  ​<Attribute Name="Channel" Type="stringlist"></Attribute>​

3) Copy/Paste the following snippet to the init.py:

import mari
mari.gl_render.registerCustomNodeFromXMLFile("Custom_Node","path/to/customNode.xml")

4) Edit the above for the current custom_node path and save the file.

5) Launch Mari, open the Example Head project, and add the custom node to the Node Graph.

6) Save and close the project, then re-open it, observing any message prompts.

Expected behavior
The project should open without additional message prompts.

Actual behavior
A message prompt for Convert Layers is given when opening a project with the custom node featuring the Channels attribute.

Workaround
There is no available workaround at this time.

Reproduced by Support in
Mari 4.6v3 - Windows 10, macOS 10.13.6

Mari 4.6v1 - Windows 10

Mari 4.5v1 - Windows 10

Mari 4.0v1 - Windows 10

Mari 3.0v1 - Windows 10

Mari 2.6v5 - Windows 10

Earliest version tested
Mari 2.6v5 - This issue appears to be in all versions of the product