Incorrect type reported on hover with implicit optional parameter

[decorator-factory]

Code:

def f(x: str = None):
    return x + "foo"

If you put a reveal_type(x) in the middle, it shows str | None correctly.
However, if you hover over x, you see just str.

Seems at least confusing to me.

[erictraut]

I agree this looks like a bug. I've created a corresponding issue in the pyright issue tracker.

[erictraut]

This will be fixed in the next release.

[bschnurr]

This issue has been fixed in version 2021.12.0, which we've just released. You can find the changelog here: CHANGELOG.md

[hadim]

I don't know whether I should open a new ticket or not but it seems like the Optional implicit type is not assigned anymore with = None. It affects all my source code since 1-2 weeks now (updated VSCode version).

See the below example:

def hello_world(value: str = None):
    print(value)

hello_world()

The code also seems valid according to mypy:

$ mypy type_test.py 
Success: no issues found in 1 source file

[erictraut]

@hadim, this was an intentional change. About a year ago, PEP 484 was updated to recommend that type checkers do not use an implicit Optional by default. We decided to give users a bit of time before changing this default, but we did so recently. If you want the old (now deprecated) behavior, you can set strictParameterNoneValue to "false".

If you are actively maintaining your code base, I'd encourage you to start moving away from implicit Optional.

[hadim]

Thanks @erictraut. It makes sense and I'll switch my codebase to this practice from now on.