python pydantic typed dict validation

pydantic_typed_dict.py

from functools import wraps
from typing import TypedDict

from pydantic import BaseModel, validate_arguments


def replace_typed_dict_annotations(annotations):
    new_annotations = {}
    for k, T in annotations.items():
        if type(T).__name__ == '_TypedDictMeta':
            class M(TDict):
                __annotations__ = replace_typed_dict_annotations(T.__annotations__)

            M.__name__ = T.__name__
            new_annotations[k] = M
        else:
            new_annotations[k] = T
    return new_annotations


def validate_args(fn):
    def f(*args, **kwargs):
        pass

    @wraps(fn)
    def wrapper(*args, **kwargs):
        f(*args, **kwargs)
        return fn(*args, **kwargs)

    wrapper.__annotations__ = replace_typed_dict_annotations(fn.__annotations__)

    return validate_arguments(wrapper)


class TDict(BaseModel):
    class Config:
        extra = 'forbid'
        arbitrary_types_allowed = True

    @classmethod
    def __get_validators__(cls):
        yield from super().__get_validators__()
        yield cls.validate

    @classmethod
    def validate(cls, v):
        if not isinstance(v, dict):
            raise TypeError('dict type expected')
        return cls(**v).dict()

class D(TypedDict):
    z: int

class A(TypedDict):
    x: int
    y: str
    d: D


@validate_args
def foo(a: A) -> int:
    print(type(a))
    return a


print(foo({'x': 1, 'y': '2', 'd': {'z': 3}}))
print(foo({'x': 1, 'y': [], 'z': 22, 'd': []}))

# OUT:
# <class 'dict'>
# {'x': 1, 'y': '2', 'd': {'z': 3}}
# ...
# pydantic.error_wrappers.ValidationError: 3 validation errors for Foo
# a -> y
#   str type expected (type=type_error.str)
# a -> d
#   dict type expected (type=type_error)
# a -> z
#   extra fields not permitted (type=value_error.extra)

workaround for samuelcolvin/pydantic#760