[BUG] Null value if the field has an alias

Describe the bug A model defined by a field with an alias gives a null value in the response.

To Reproduce Steps to reproduce the behavior:

1. Create the following files using the template full-stack-fastapi-postgresql

• models/test.py

from typing import List
from pydantic import BaseModel, Schema


class metadata(BaseModel):
    title: str = None


class baseType(BaseModel):
    metadata_: List[metadata] = Schema(None, alias="metadata")


class testSummary(baseType):
    tid: str = ...


class testCollection(BaseModel):
    tests: List[testSummary] = None


class TestBase(testSummary):
    pass


class TestCreate(TestBase):
    pass


# Properties shared by models stored in DB
class TestInDBBase(TestBase):
    id: int = None
    owner_id: int

    class Config:
        orm_mode = True


# Properties to return to client
class Test(TestInDBBase):
    pass

• db_models/test.py

from sqlalchemy import Column, ForeignKey, Integer, String
from sqlalchemy.dialects import postgresql
from sqlalchemy.orm import relationship

from app.db.base_class import Base


class Test(Base):

    __tablename__ = 'test'

    id                 = Column(Integer, primary_key=True, index=True)
    tid                = Column(String, index=True)
    title              = Column(String, index=True)
    metadata_          = Column(postgresql.JSONB, default=[])
    owner_id           = Column(Integer, ForeignKey("user.id"))
    owner              = relationship("User", back_populates="tests")

1. Add a path operation function with

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session

from app import crud
from app.models.test import testCollection, TestCreate, Test
from app.api.utils.db import get_db
from app.api.utils.security import get_current_active_user
from app.db_models.user import User as DBUser


router = APIRouter()


import logging


logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)


@router.get(
    "/tests/",
    operation_id="getTests",
    response_model=testCollection,
    status_code=200
)
def read_wps_tests(
    db: Session = Depends(get_db),
    skip: int = 0,
    limit: int = 100,
):
    """
    Retrieve available tests.
    """
    tests = crud.test.get_multi(db, skip=skip, limit=limit)
    if not tests:
        logger.info(f"======> The test collection is empty")
        tests = []
    return {"tests": tests}


@router.post(
    "/tests/",
    operation_id="createTest",
    response_model=Test,
    status_code=201,
    include_in_schema=True
)
def create_wps_test(
    *,
    db: Session = Depends(get_db),
    test_in: TestCreate,
    current_user: DBUser = Depends(get_current_active_user),
):
    """
    Create new wps test.
    """
    if not crud.user.is_superuser(current_user):
        raise HTTPException(
            status_code=403,
            detail="You are not allowed to register tests"
        )
    elif crud.test.get_by_tid(db_session=db, tid=test_in.tid):
        raise HTTPException(
            status_code=422,
            detail="The test has been already created"
        )
    test = crud.test.create(
        db_session=db,
        test_in=test_in,
        owner_id=current_user.id
    )
    return test

1. Make a POST with a payload of

{
  "metadata": [
    {
      "title": "my title"
    }
  ],
  "tid": "pippo”
}

1. Make GET request and see error

Expected behavior Before 0.30.0 I’ve seen it working but the response had "metadata": null

Environment:

• OS: template with containers
• FastAPI 0.30.0

[tiangolo]

Thanks for reporting back and closing the issue @francbartoli ! 🎉

[stefanondisponibile]

Since I noticed some errors in my code (don’t know why the heck hadn’t put the response model into the decorator, sorry about that), I decided to cut to the chase and set up a little app for it. Looks ok to me, try that out: git clone https://gitlab.com/stefanondisponibile/fastapi_327