Alias ignored on custom root type

[okonos]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.8.2
            pydantic compiled: True
                 install path: /home/user/.local/share/virtualenvs/pydanticvenv/lib/python3.9/site-packages/pydantic
               python version: 3.9.5 (default, Nov 18 2021, 16:00:48)  [GCC 10.3.0]
                     platform: Linux-5.11.0-41-generic-x86_64-with-glibc2.33
     optional deps. installed: ['typing-extensions']

The provided snippet works fine on 1.7.4, but does not on 1.8.x.
git bisect points to #2238 as first bad commit. The culprit seems to be the validate method, where value is wrapped with the dict under ROOT_KEY, leading to validation error.

from pydantic import BaseModel, Field


class NestedModel(BaseModel):
    __root__: int = Field(..., alias='x')


class MyModel(BaseModel):
    v: NestedModel


MyModel(**{'v': {'x': 2}})
# pydantic.error_wrappers.ValidationError: 1 validation error for MyModel
# v -> x
#   field required (type=value_error.missing)

[Kludex]

Since this is stale, I'll be closing it. Sorry for the long delay.

I don't think the behavior you describe was ever supposed to be supported, since you can achieve it with the following:

from pydantic import BaseModel
from typing_extensions import TypedDict


class NestedModel(TypedDict):
    x: int


class MyModel(BaseModel):
    v: NestedModel


MyModel(**{"v": {"x": 1}})

Note

The above works on either V1 and V2.

Hope this is enough. If not, please open a new issue. 🙏