Typing complaints for @validator decorator

[jannikmi]

For the following minimal code example i get the typing complaint "Method should have "self" as first argument":

from typing import Literal

import pydantic


class BaseModelClass(pydantic.BaseModel):
    """
    Doctolib search criteria
    """

    attribute: Literal["a", "b"]

    @pydantic.validator("attribute", pre=True)
    def lower_case_str(cls, v: str) -> str:
        return v.lower()


x = BaseModelClass(attribute="a")
print(x)

y = BaseModelClass(attribute="A")
print(y)

When i add @classmethod the complaint goes away:

    @classmethod
    @pydantic.validator("attribute", pre=True)
    def lower_case_str(cls, v: str) -> str:

... but the validation won't get through:

pydantic.error_wrappers.ValidationError: 1 validation error for BaseModelClass
attribute
  unexpected value; permitted: 'a', 'b' (type=value_error.const; given=A; permitted=('a', 'b'))

When i reverse the order everything works fine:

    @pydantic.validator("attribute", pre=True)
    @classmethod
    def lower_case_str(cls, v: str) -> str:

however i get the warning "This decorator will not receive a callable it may expect; the built-in decorator returns a special object"

How to solve this?

[DMRobertson]

Is this fixed by #4102?

[dmontagu]

This is now fixed in v1 and v2