Import from xml and populate nodes avoiding duplicates

[zarch]

Dear all,

I would like to start and initialize a opcua server with the following logic steps:

1. set endpoint and uri;
2. load and import nodes from xml if the file exists;
3. load desired nodes based on some rules and avoiding to create a new node if already exists
4. export the updated version of the xml file.

It seems simple but I'm failing on point 3.
The code is always creating the new nodes and is not able to find the imported ones.

So to give an example I'm importing the following nodes (created with the first run of the program):

$ uv run opcua.py
...
ns=2;i=1 | object_type | QualifiedName(NamespaceIndex=2, Name='ElectricPanel')
ns=2;i=2 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l1')
ns=2;i=3 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l2')
ns=2;i=4 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l3')
ns=2;i=5 | object | QualifiedName(NamespaceIndex=2, Name='factory')
ns=2;i=6 | object | QualifiedName(NamespaceIndex=2, Name='ElPnl0')
ns=2;i=7 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l1')
ns=2;i=8 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l2')
ns=2;i=9 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l3')
...

but the server nodes at the end of the main_server function the second time that I execute the code is printing the following nodes:

$ uv run opcua.py
...
ns=2;i=1 | object_type | QualifiedName(NamespaceIndex=2, Name='ElectricPanel')
ns=2;i=2 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l1')
ns=2;i=3 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l2')
ns=2;i=4 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l3')
ns=2;i=5 | object | QualifiedName(NamespaceIndex=2, Name='factory')
ns=2;i=6 | object | QualifiedName(NamespaceIndex=2, Name='ElPnl0')
ns=2;i=7 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l1')
ns=2;i=8 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l2')
ns=2;i=9 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l3')
ns=2;i=10 | object_type | QualifiedName(NamespaceIndex=2, Name='ElectricPanel')
ns=2;i=11 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l1')
ns=2;i=12 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l2')
ns=2;i=13 | variable | QualifiedName(NamespaceIndex=2, Name='ElectricPanel/current_l3')
ns=2;i=14 | object | QualifiedName(NamespaceIndex=2, Name='factory')
ns=2;i=15 | object | QualifiedName(NamespaceIndex=2, Name='ElPnl0')
ns=2;i=16 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l1')
ns=2;i=17 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l2')
ns=2;i=18 | variable | QualifiedName(NamespaceIndex=2, Name='ElPnl0/cur_l3')
...

To find if a node already exists I've defined the following function:

async def find_node_by_browsname(server: Server, idx: Idx, bname: str) -> None | Node:
    """Find node by browse name."""
    # check if the node already exists
    path = [
        ua.QualifiedName(Name=bname, NamespaceIndex=idx),
    ]
    try:
        node = await server.get_node(server.get_root_node()).get_child(path)
    except Exception as exc:
        log.debug(f"{bname} not found, Exception raised: {exc}")
    else:
        return node

Do you spot anything that is it clearly wrong? Have I miss some other way that I should I use / check?

The full code is a bit lengthy and i put it inside a dedicated gist