"None" in Python code breaks code suggestions in vscode

Seems to be related to type annotations.

If you remove variable type annotation in Card class in cards_projsrccardsapi.py file. Then the intellisense will work fine.

Source code:

class Card:
    summary: str = None
    owner: str = None
    state: str = "todo"
    id: int = field(default=None, compare=False)

change into:

class Card:
    summary = None
    owner = None
    state = "todo"
    id = field(default=None, compare=False)

If you only remove type annotations for some variables, like below.

class Card:
    summary: str = None
    owner: str = None
    state = "todo"
    id = field(default=None, compare=False)

Then when the variable with the type annotation is assigned none, the following intellisense will be invalid.

summary is None, the following code cannot get suggestions

summary is not None, the following code can get suggestions

summary is not None, but owner is None, the following code cannot get suggestions

If you are going to use type hints, I suggest you configure vscode to do Mypy type checking to avoid these kind of errors.

If you annotate the type as str and then assign it a value of None, and you have Mypy type checking, this will trigger an incompatible type warning.

Because you have annotated the type as str. Vscode will think that the 2nd assertion is unreachable:

c = Card()
assert c.summary is None # assertion always fails because c.summary is string
assert c.owner is None # this statement is unreachable

The 2nd assertion
Screenshot shows that vscode thinks 2nd assertion is never reached because the 1st assertion will always fail because a string type will never be none.

To correct use the Optional type hint when assigning None.

from dataclasses import asdict
from dataclasses import dataclass
from dataclasses import field

from typing import Optional, Any, Dict

@dataclass
class Card:
    summary: Optional[str] = None
    owner: Optional[str] = None
    state: str = "todo"
    id: Optional[int] = field(default=None, compare=False)

    @classmethod
    def from_dict(cls, d: Dict[str, Any]) -> "Card":
        return Card(**d)
    def to_dict(self) -> Dict[str, Any]:
        return asdict(self)

As a final point, I think you have absolutely done the right thing. In my view, autocomplete is critically important in avoiding mistakes. If autocomplete isn’t working you should stop, figure out why, and do not continue until you get autocomplete working again.

This seems to be a quirk of VS Code on Ubuntu combined with sloppy type hinting.

I really should have used the types as mpette noted, using Optional[X] = None:

@dataclass
class Card:
    summary: Optional[str] = None
    owner: Optional[str] = None
    state: str = "todo"
    id: Optional[int] = field(default=None, compare=False)

Or even the newer bar form X|None:

@dataclass
class Card:
    summary: str|None = None
    owner: str|None = None
    state: str = "todo"
    id: int|None = field(default=None, compare=False)

However, even on a mac, the second form seems to confuse VSCode.

Also, VSCode on my mac seems to deal with the original form just fine. Odd that it’s different behavior on Ubuntu.