Field(alias=...) not honored by validate_arguments decorator

[jwodder]

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
            pydantic compiled: True
                 install path: /Users/jwodder/work/sand/pydantic/venv/lib/python3.9/site-packages/pydantic
               python version: 3.9.2 (default, Feb 19 2021, 17:43:04)  [Clang 12.0.0 (clang-1200.0.32.29)]
                     platform: macOS-11.2.1-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

The following program:

from pydantic import Field, validate_arguments
from pydantic.typing import Annotated

@validate_arguments
def foo(bar: Annotated[int, Field(alias="quux")]):
    print(bar)

foo(quux=42)

fails with the following error:

Traceback (most recent call last):
  File "/Users/jwodder/work/sand/pydantic/hyphen03.py", line 8, in <module>
    foo(quux=42)
  File "pydantic/decorator.py", line 52, in pydantic.decorator.validate_arguments.validate.wrapper_function
  File "pydantic/decorator.py", line 145, in pydantic.decorator.ValidatedFunction.call
  File "pydantic/decorator.py", line 142, in pydantic.decorator.ValidatedFunction.init_model_instance
  File "pydantic/main.py", line 391, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 2 validation errors for Foo
bar
  field required (type=value_error.missing)
kwargs
  unexpected keyword argument: 'quux' (type=type_error)

The alias parameter to Field evidently has no effect when used with validate_arguments. I can find no mention of this limitation in the docs, and so I assume it is a bug.

[samuelcolvin]

Related to #2176.

I would argue that this is a feature request, rather than a bug, we don't say anywhere (AFAIK) that alias on is supported with validate_assignment.

I do think support would make sense though.

[spawn-guy]

@samuelcolvin we are experiencing same issues. this started happening after our recent dependency update to ==1.8 from ==1.7.3.

previously, we had a chance to populate by alias or/and by resulting field name. now this feature is broken.

class SomeModel(BaseModel):
    some_field: str = Field(..., alias='some_old_field_name')

    class Config:
        extra: Extra.ignore
        allow_population_by_alias = True

then both of this worked

SomeModel(some_field='value')
SomeModel(some_old_field_name='value')

now we receive:

pydantic.error_wrappers.ValidationError: 3 validation errors for SomeModel
some_old_field_name
  field required (type=value_error.missing)

we will rollback to 1.7.* for now

[PrettyWood]

@spawn-guy You just need to have a quick look at the changelog.
Right at the beginning

Breaking Change, remove old deprecation aliases from v1, #2415 by @samuelcolvin:
    ...
    remove Config.allow_population_by_alias which was replaced by Config.allow_population_by_field_name
    ...

So just use allow_population_by_field_name = True and it works

[erudin]

It seems that is issue is already fixed by PR #3019.