Extra inputs are not permitted with AliasChoices

[levsh]

Hi!
Example code to reproduce:

from unittest import mock
from pydantic import AliasChoices, Field
from pydantic_settings import BaseSettings

def test_settings():
    class Settings(BaseSettings):
        field: str = Field(validation_alias=AliasChoices("field", "my_field"))

    env = {}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings(field="bar").field == "bar"  # Ok

    env = {"my_field": "foo"}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings().field == "foo"  # Ok

    env = {"my_field": "foo"}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings(field="bar").field == "bar"  # Not ok, raise ValidationError

Third case raises

        env = {"my_field": "foo"}
        with mock.patch.dict(os.environ, env, clear=True):
>           assert Settings(field="bar").field == "bar"

tests/.../test_settings.py: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

__pydantic_self__ = <[AttributeError('__pydantic_extra__') raised in repr()] Settings object at 0x7efdbe6eca40>, _case_sensitive = None, _env_prefix = None, _env_file = PosixPath('.')
_env_file_encoding = None, _env_nested_delimiter = None, _secrets_dir = None, values = {'field': 'bar'}

    def __init__(
        __pydantic_self__,
        _case_sensitive: bool | None = None,
        _env_prefix: str | None = None,
        _env_file: DotenvType | None = ENV_FILE_SENTINEL,
        _env_file_encoding: str | None = None,
        _env_nested_delimiter: str | None = None,
        _secrets_dir: str | Path | None = None,
        **values: Any,
    ) -> None:
        # Uses something other than `self` the first arg to allow "self" as a settable attribute
>       super().__init__(
            **__pydantic_self__._settings_build_values(
                values,
                _case_sensitive=_case_sensitive,
                _env_prefix=_env_prefix,
                _env_file=_env_file,
                _env_file_encoding=_env_file_encoding,
                _env_nested_delimiter=_env_nested_delimiter,
                _secrets_dir=_secrets_dir,
            )
        )
E       pydantic_core._pydantic_core.ValidationError: 1 validation error for Settings
E       my_field
E         Extra inputs are not permitted [type=extra_forbidden, input_value='foo', input_type=str]
E           For further information visit https://errors.pydantic.dev/2.2/v/extra_forbidden

Expect environment variable 'my_field' to be ignored in favor of explicitly passed field='bar'.

pydantic                  2.2.1
pydantic_core             2.6.1
pydantic-settings         2.0.3

Selected Assignee: @samuelcolvin

[hramezani]

Thanks @levsh for reporting this issue 🙏

By default extra config in pydantic-settings is forbid. That's why you see the error.

[levsh]

@hramezani thank you for reply.
My goal is to get a Settings model with property name 'field' and possibility of a default value from environment variable 'my_field'. With extra = 'forbid' on whole model to prevent other fields except 'field' and 'my_field'.
Settings.field should be initialized directly as init 'field' argument: Settings(field="bar") or from env variable 'my_field': Settings()
But if env varialbe 'my_field' exists it is not possible to set 'field' directly

[hramezani]

Its intended behavior inPydantic. I think in this case its better to raise an error instead of losing the data.

from pydantic import AliasChoices, BaseModel, ConfigDict, Field

class Settings(BaseModel):
    model_config = ConfigDict(extra='forbid', populate_by_name=True)

    field: str = Field(alias=AliasChoices("field", "my_field"))

Settings(my_field='foo', field='bar')
"""
pydantic_core._pydantic_core.ValidationError: 1 validation error for Settings
my_field
  Extra inputs are not permitted [type=extra_forbidden, input_value='foo', input_type=str]
    For further information visit https://errors.pydantic.dev/2.2/v/extra_forbidden
"""

[levsh]

I migrate my application from Pydantic v1 to v2. My current code is

class Settings(BaseSettings):
    field: str = Field(env="my_field")
    class Config:
        extra="forbid"

so i can instantiate my service Settings from env variable my_field

settings = Settings()

or do it explicit

settings = Settings(field="abc")

Unfortunately, according to docs env option is removed in v2, so i can't move my current logic to v2 without change it.
Only use extra='ignore'

Thanks for the clarifications

[hramezani]

Why you don't use alias instead of env:

field: str = Field(alias="my_field")

[levsh]

@hramezani with field: str = Field(alias="my_field")

import os
from typing import Optional
from unittest import mock
from pydantic import AliasChoices, Field
from pydantic_settings import BaseSettings

def test_settings():
    class Settings(BaseSettings):
        field: str = Field(alias="my_field")

    # 1
    env = {}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings(field="bar").field == "bar"  # 1

    # 2
    env = {"my_field": "foo"}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings().field == "foo"  # 2

    # 3
    env = {"my_field": "foo"}
    with mock.patch.dict(os.environ, env, clear=True):
        assert Settings(field="bar").field == "bar"  # 3

test_settings()

Exception

ValidationError                           Traceback (most recent call last)
Cell In[2], line 1
----> 1 test_settings()

Cell In[1], line 14, in test_settings()
     12 env = {}
     13 with mock.patch.dict(os.environ, env, clear=True):
---> 14     assert Settings(field="bar").field == "bar"  # 1
     16 # 2
     17 env = {"my_field": "foo"}

File ~/.pyenv/versions/3.11.4/lib/python3.11/site-packages/pydantic_settings/main.py:71, in BaseSettings.__init__(__pydantic_self__, _case_sensitive, _env_prefix, _env_file, _env_file_encoding, _env_nested_delimiter, _secrets_dir, **values)
     60 def __init__(
     61     __pydantic_self__,
     62     _case_sensitive: bool | None = None,
   (...)
     69 ) -> None:
     70     # Uses something other than `self` the first arg to allow "self" as a settable attribute
---> 71     super().__init__(
     72         **__pydantic_self__._settings_build_values(
     73             values,
     74             _case_sensitive=_case_sensitive,
     75             _env_prefix=_env_prefix,
     76             _env_file=_env_file,
     77             _env_file_encoding=_env_file_encoding,
     78             _env_nested_delimiter=_env_nested_delimiter,
     79             _secrets_dir=_secrets_dir,
     80         )
     81     )

File ~/.pyenv/versions/3.11.4/lib/python3.11/site-packages/pydantic/main.py:159, in BaseModel.__init__(__pydantic_self__, **data)
    157 # `__tracebackhide__` tells pytest and some other tools to omit this function from tracebacks
    158 __tracebackhide__ = True
--> 159 __pydantic_self__.__pydantic_validator__.validate_python(data, self_instance=__pydantic_self__)

ValidationError: 2 validation errors for Settings
my_field
  Field required [type=missing, input_value={'field': 'bar'}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.1/v/missing
field
  Extra inputs are not permitted [type=extra_forbidden, input_value='bar', input_type=str]
    For further information visit https://errors.pydantic.dev/2.1/v/extra_forbidden