Is it intentional that Field(None) leads to typing errors but Field(default=None) does not?

[smorokin]

Sorry, I could not really find an answer - just that something very similar was fixed (e.g. #3617)

Example Code:

from pydantic import BaseModel, Field


class User1(BaseModel):
    name: str | None = Field(None)


class User2(BaseModel):
    name: str | None = Field(default=None)


u1 = User1() # mypy & pyright error: Missing named argument "name" for "User1"  [call-arg]

u2 = User2() # no typing error

The example works either way, but both pyright and mypy report a typing error. Is this by design?

[Viicos]

Pydantic relies on PEP 681 to make type checkers aware of the signature of models. The PEP requires Field arguments to be keyword only, but default can be set as a positional argument for historical reasons (it was here before PEP 681 was a thing, and was kept as is for compatibility reasons).

It is thus recommended to use the explicit default keyword argument, or, as an alternative, name: str | None = None (or using Annotated, see #7379 (reply in thread)).

[smorokin]

Thank you, that makes it so much clearer!