EnvSettingsSource does not respect populate_by_name for aliased fields #452
Description
It looks like the logic to extract fields from the environment (e.g. os.environ) only respects the alias for aliased Fields vs. also allowing for env vars to be set by name when populate_by_name=True in the model config.
Simple reproduce script:
import os
from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict
class AppSettings(BaseSettings):
SETTING_NAME: str = Field("default", alias="ALIAS_NAME")
model_config = SettingsConfigDict(populate_by_name=True, case_sensitive=True)
if __name__ == "__main__":
os.environ['SETTING_NAME'] = 'by-name'
settings = AppSettings()
print(f"{settings.SETTING_NAME=}")
os.environ['ALIAS_NAME'] = 'by-alias'
settings = AppSettings()
print(f"{settings.SETTING_NAME=}")
# Outputs:
# settings.SETTING_NAME='default'
# settings.SETTING_NAME='by-alias'Note that changing the env source to use a custom source does appear to address this, though I'm not confident this is the correct approach:
import os
from pydantic import Field
from pydantic.fields import FieldInfo
from pydantic_settings import BaseSettings, SettingsConfigDict, EnvSettingsSource, PydanticBaseSettingsSource, \
DotEnvSettingsSource
class BetterAliasEnvSettingsSource(EnvSettingsSource):
"""
Overrides the base env settings source to also respect populate_by_name when settings vars are aliased.
"""
def _extract_field_info(self, field: FieldInfo, field_name: str) -> list[tuple[str, str, bool]]:
"""
Overrides super method to add better support for aliased fields.
"""
field_info = super()._extract_field_info(field, field_name)
if field.validation_alias:
# Also add the column name if configured to allow setting by name
if self.config.get("populate_by_name"):
field_info.append((field_name, self._apply_case_sensitive(self.env_prefix + field_name), False))
return field_info
class AppSettings(BaseSettings):
SETTING_NAME: str = Field("default", alias="ALIAS_NAME")
model_config = SettingsConfigDict(populate_by_name=True, case_sensitive=True)
@classmethod
def settings_customise_sources(
cls,
settings_cls: type[BaseSettings],
init_settings: PydanticBaseSettingsSource,
env_settings: EnvSettingsSource,
dotenv_settings: DotEnvSettingsSource,
file_secret_settings: PydanticBaseSettingsSource,
) -> tuple[PydanticBaseSettingsSource, ...]:
fixed_env_settings = BetterAliasEnvSettingsSource(
settings_cls,
case_sensitive=env_settings.case_sensitive,
env_prefix=env_settings.env_prefix,
env_nested_delimiter=env_settings.env_nested_delimiter,
env_ignore_empty=env_settings.env_ignore_empty,
env_parse_none_str=env_settings.env_parse_none_str,
env_parse_enums=env_settings.env_parse_enums,
)
return (
init_settings,
fixed_env_settings,
dotenv_settings,
file_secret_settings,
)
if __name__ == "__main__":
os.environ['SETTING_NAME'] = 'by-name'
settings = AppSettings()
print(f"{settings.SETTING_NAME=}")
os.environ['ALIAS_NAME'] = 'by-alias'
settings = AppSettings()
print(f"{settings.SETTING_NAME=}")
# Outputs:
# settings.SETTING_NAME='by-name'
# settings.SETTING_NAME='by-alias'I suspect this issue may also apply to DotEnvSettingsSource, but I have not experimented as comprehensively with this one.