mypy with pydantic field_validator

Question

With pydantic, is there a way for mypy to be hinted so it doesn't raise an error in this scenario, where there's a field_validator modifying the type?

class MyModel(BaseModel):
    x: int

    @field_validator("x", mode="before")
    @classmethod
    def to_int(cls, v: str) -> int:
        return len(v)


MyModel(x='test')

Answer 1

If you're always inserting a string there, it might be better to use a computed_field. Something along this, maybe?

class MyModel(BaseModel):
    input: str

    @computed_field
    def x(self) -> int:
        return len(self.input)

I think it's very counterintuitive if you see the model with the int declaration while it would raise type errors if you put an integer inside a JSON at that place.