Pylance stops working randomly

[luabud]

From marketplace review:

it's a bit unstable sometimes, I've had some features stop working randomly

[heejaechang]

can we talk to customer?

[spokeydokeys]

I did not report this (or comment on it in the market place) but have experienced it and seen it with my colleagues too. It seems to be a relatively new issue.

The behavior is that I'm making changes to code and pylance will underline code, but even after I have satisfied the issue it continues to underline the code. For example, I was working with os.getenv earlier today in a situation like:

import os
from typing import Optional

def my_func(val: Optional[dict[str, str]] = None):
    if val is None:
        val = {"key": os.getevn("myVar")}
    ...

It correctly identified that in this case val could be [str, str | None] and underlined it. I changed the assignment to be os.getenv("myVar", "") but pylance still underlined it, even after file save or file modification then save. The only way to get it to re-evaluate this is to restart the language server (or all of VScode).

I have checked the language server outputs and not seen any obvious errors. Is there another place to look for clues?