Model with field name that shadows existing BaseModel attribute leads to unexpected behavior

Hello, First of all this is an awesome project, I want to use it in all my tools 😃.

I ran into a small issue: when defining a model that has a field with the same name as one of BaseModel’s existing attributes/methods, the field gets parsed but cannot be retrieved:

class BadModel(BaseModel):
    schema: str

obj = BaseModel(**{'schema': 'abc'})
print(obj.schema)

This prints <bound method BaseModel.schema of <class 'pydantic.main.BaseModel'>> instead of abc.

This makes perfect sense when looking at the code but is a bit unexpected. To be honest, I’m not sure what the “right” behavior should be here?

[layday]

Well, that kind of shadowing isn’t compatible with type checking in Python; you cannot have a field with a disparate type on a sub-model. You can define your class methods on the metaclass so that they are not present on instances of Users but your type checker (assuming you use one) won’t know what to do with them either:

from pydantic.main import ModelMetaclass, BaseModel


class UsersMeta(ModelMetaclass):
    def find(cls, pk: int) -> 'Users': ...


class Users(BaseModel, metaclass=UsersMeta):
    find: int

Users.find  # Should this be `int` or `(pk: int) -> Users`?

Anyway, this will work without requiring any changes to Pydantic, assuming that you don’t step on any of its own methods.

[mreschke]

@layday thanks I have seen that interesting thread. But that discussion is more around public instance variables as opposed to class variable vs instance variable shadowing. Obviously you wouldn’t want to remove the utils.validate_field_name at this point since its been there since 0.12. But if we can pass in config: Type['BaseConfig'] and make it a config property so we can control the shadow behavior from a config that would be a flexible solution.