How to use `from_orm` if the pydantic model defines aliases? - orm

Question

Though the pydantic's ORM mode is documented here, unfortunately there is no documentation for usage with aliases.
How to use from_orm if the pydantic model defines aliases?
It seems that the from_orm factory forgets about all non-aliased names if aliases exist. - See error message and the corresponding code below. Is that a bug or a feature?
The code snippet below fails unexpectedly with a validation error:
pydantic.error_wrappers.ValidationError: 1 validation error for SimpleModel
threeWordsId
field required (type=value_error.missing)
from sqlalchemy import Column, String
from sqlalchemy.ext.declarative import declarative_base
from pydantic import BaseModel, Field
Base = declarative_base()
class SimpleOrm(Base):
__tablename__ = 'simples'
three_words_id = Column(String, primary_key=True)
class SimpleModel(BaseModel):
three_words_id: str = Field(..., alias="threeWordsId")
class Config:
orm_mode=True
simple_orm = SimpleOrm(three_words_id='abc')
simple_oops = SimpleModel.from_orm(simple_orm)

Answer 1

Use allow_population_by_field_name = True in config.
Like
from sqlalchemy import Column, String
from sqlalchemy.ext.declarative import declarative_base
from pydantic import BaseModel, Field
Base = declarative_base()
class SimpleOrm(Base):
__tablename__ = 'simples'
three_words_id = Column(String, primary_key=True)
class SimpleModel(BaseModel):
three_words_id: str = Field(..., alias="threeWordsId")
class Config:
orm_mode = True
allow_population_by_field_name = True
# allow_population_by_alias = True # in case pydantic.version.VERSION < 1.0
simple_orm = SimpleOrm(three_words_id='abc')
simple_oops = SimpleModel.from_orm(simple_orm)
print(simple_oops.json()) # {"three_words_id": "abc"}
print(simple_oops.json(by_alias=True)) # {"threeWordsId": "abc"}
from fastapi import FastAPI
app = FastAPI()
#app.get("/model", response_model=SimpleModel)
def get_model():
# results in {"threeWordsId":"abc"}
return SimpleOrm(three_words_id='abc')