Python type converter bug #430

Activity

1. github-actions

   added

   triage-needed

   on Jul 4, 2025
2. Erik De Bonte (debonte)

   added

   bugIssue identified by VS Code Team member as probable bugIssue identified by VS Code Team member as probable bug

   and removed

   triage-needed

   on Jul 22, 2025
3. debonte commented on Jul 22, 2025

   

   Erik De Bonte (debonte)

   on Jul 22, 2025

   Contributor

   More actions

   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}")
4. mjpieters commented on Nov 26, 2025

   

   Martijn Pieters (mjpieters)

   on Nov 26, 2025

   More actions

   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)

   👍React with 👍1Reacted by Shahriar Heidrich

   ❤️React with ❤️1Reacted by Shahriar Heidrich
5. Mohammed Elwardi Fadeli (FoamScience)

   added a commit that references this issue on Feb 10, 2026

   fix: workaround microsoft/lsprotocol#430 for ty compatibility

   68eac53
6. Shubham-Padkonde commented on Sep 20, 2026

   

   Shubham Padkonde (Shubham-Padkonde)

   on Sep 20, 2026

   More actions

   This is the same root cause as #462, and #466 fixes it.

   NotebookDocumentFilterWithCells.notebook is typed Optional[Union[str, NotebookDocumentFilterNotebookType, NotebookDocumentFilterScheme, NotebookDocumentFilterPattern]], but _hooks.py registers _notebook_filter_hook only for the non-optional union, so the optional form has no structure hook — which is the NoneType you spotted in the message.

   Checked against your payload on current main (cattrs 26.2.0):

   # main
   FAIL ClassValidationError While structuring InitializeResult (1 sub-exception)
     cattrs.errors.StructureHandlerNotFoundError: Unsupported type:
     str | NotebookDocumentFilterNotebookType | NotebookDocumentFilterScheme | NotebookDocumentFilterPattern | None
   
   # main + #466
   OK NotebookDocumentSyncOptions(notebook_selector=(NotebookDocumentFilterWithCells(
        cells=(NotebookCellLanguage(language='python'),), notebook=None),), save=False)
   

   So nothing extra is needed here — this issue should close along with #466.