Python type converter bug

[peske]

When I try to use lsprotocol.converters.get_converter to parse the following (only the key part included):

{
    "jsonrpc": "2.0",
    "id": "1195cd79-60e6-412b-bc6a-9c77b6e5d7c1",
    "result": {
        "capabilities": {
            "notebookDocumentSync": {
                "notebookSelector": [
                    {
                        "cells": [
                            {
                                "language": "python"
                            }
                        ]
                    }
                ],
                "save": false
            }
        }
    }
}

I'm getting the following error (again, only the key part included):

cattrs.errors.StructureHandlerNotFoundError: Unsupported type: typing.Union[str, lsprotocol.types.NotebookDocumentFilterNotebookType, lsprotocol.types.NotebookDocumentFilterScheme, lsprotocol.types.NotebookDocumentFilterPattern, NoneType]. Register a structure hook for it.

I'm not sure, but thing that looks suspicious to me there is NoneType.

[debonte]

Not sure what's wrong yet, but I was able to repro the issue with the code below.

The issue seems to have something to do with handling NotebookDocumentFilterWithNotebook vs NotebookDocumentFilterWithCells. The input has cells, but the error is about parsing notebook (the NotebookDocumentFilter type).

import json
import lsprotocol.converters
from lsprotocol.types import InitializeResult


input = """{
    "capabilities": {
        "notebookDocumentSync": {
            "notebookSelector": [
                {
                    "cells": [
                        {
                            "language": "python"
                        }
                    ]
                }
            ],
            "save": false
        }
    }
}"""

converter = lsprotocol.converters.get_converter()

obj = json.loads(input)

try:
    converter.structure(obj, InitializeResult)
except Exception as e:
    while getattr(e, 'exceptions', None) != None:
        e = e.exceptions[0]
    print(f"Error: {e}")

[mjpieters]

The reproducer can be simplified to:

import lsprotocol.converters
import lsprotocol.types
converter = lsprotocol.converters.get_converter()
object_ = {"cells": [{"language": "python"}]}
converter.structure(object_, lsprotocol.types.NotebookDocumentFilterWithCells)

The issue is with the notebook field:

    noteook: Optional[Union[str, NotebookDocumentFilter]] = attrs.field(default=Nbone)
    """The notebook to be synced If a string
    value is provided it matches against the
    notebook type. '*' matches every notebook."""

for which there is no hook defined, because it is optional. There is only a hook for Union[str, NotebookDocumentFilter] which doesn't account for None.

The work-around is to register such a hook:

from typing import Any

@converter.register_structure_hook
def _(
    object_: Any, _: object
) -> (
    str
    | lsprotocol.types.NotebookDocumentFilterNotebookType
    | lsprotocol.types.NotebookDocumentFilterScheme
    | lsprotocol.types.NotebookDocumentFilterPattern
    | None
):
    if object_ is None:
        return None
    elif isinstance(object_, str):
        return str(object_)
    elif "notebookType" in object_:
        return converter.structure(
            object_, lsprotocol.types.NotebookDocumentFilterNotebookType
        )
    elif "scheme" in object_:
        return converter.structure(object_, lsprotocol.types.NotebookDocumentFilterScheme)
    else:
        return converter.structure(object_, lsprotocol.types.NotebookDocumentFilterPattern)