Editing User.config creates a corrupted file, even with valid XML

[ShareUser]

So, as a follow up to this post: https://community.esri.com/t5/arcgis-pro-questions/set-pro-s-default-settings-programmatically/m-p/1...

I've been trying to edit user.config. I'm having no problem editing nodes that already exist in the config file.

Here's where I'm having trouble:

If the node that I want (e.g. RequireExplicitStartEditing) isn't there, I make a new one

    def newTag(tree, tag, section, value, serialType): 
               #XML Tree Object, 
               #"RequireExplicitStartEditing",
               #"Editing", 
               #"True", 
               #"String")
        
        parEl = tree.find(f"./userSettings/ArcGIS.Desktop.{section}.Settings")
        createFols = ET.SubElement(parEl,
                                  "setting", 
                                  attrib = {"name": tag, 
                                           "serialAs":serialType})
                                           
        child = ET.SubElement(createFols, "value")
        child.text = value
        return

This works great. It creates valid XML and no Python errors.

The issue I'm having is that opening up Pro after this will either cause it to crash OR give me the following:

If I click "Yes", I get this message, which destroys the config file and undoes my work.

So, what am I doing wrong? I'd like to be able to create the necessary settings nodes on a fresh config file for each user.

Again, if the node is already there, I can edit the values no problem and have it work (not including my code for this one). It's when they're new that I have issues.

I've confirmed that the sections match up correctly in the configSections node (you need to add two sections for editing) and played with the node order, and I just can't get it to work.

[HaydenWelch]

Have you run a diff on the original config and the new config? I just tried it with this code:

import xml.etree.ElementTree as ElementTree

def newTag(tree: ElementTree, tag: str, section: str, value: ..., serialType: str = "String"):
    """Create a new tag in the XML tree object.
    Args:
        tree (ElementTree): The XML tree object.
        tag (str): The name of the tag.
        section (str): The section of the XML tree object.
        value (str): The value of the tag.
        serialType (str): The serial type of the tag. Defaults to "String".
    """
    parEl: ElementTree.Element = tree.find(f"./userSettings/ArcGIS.Desktop.{section}.Settings")
    createFols = ElementTree.SubElement(parEl,
                              "setting", 
                              attrib = {"name": tag, 
                                       "serialAs":serialType})
    child = ElementTree.SubElement(createFols, "value")
    child.text = value
    return

if __name__ == "__main__":
    tree = ElementTree.parse(r"<old_config>")
    newTag(tree, "RequireExplicitStartEditing", "Editing", "True")
    tree.write(r"<new_config>")

And the output XML was missing the xml version tag and the xmlns:xsi property (Generated on Right, Original on Left):

Those were the only differences between the files beyond some slight whitespace and line formatting that shouldn't effect anything