TestClient: how to test overwrites in the Config of an input (pydantic) model?

[camold]

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Example Code

###### fastapi_extra.py
import fastapi
from pydantic import BaseModel


class MyModel(BaseModel):
    i: int

    class Config:
        extra = "ignore"


def create_app():

    app = fastapi.FastAPI()

    @app.post("/")
    def test(m: MyModel):
        return [m.i, MyModel.Config.extra]

    return app

########### test_fastapi_extra.py
import pytest
from fastapi.testclient import TestClient

import fastapi_extra

# overwrite from "ignore" to "forbid"
fastapi_extra.MyModel.Config.extra = "forbid"


@pytest.fixture
def test_app():
    yield TestClient(fastapi_extra.create_app())


def test_root(test_app):
    # send a message with an additional attribute
    r = test_app.post("/", json={"i": 2, "foo": "bar"})
    assert r.json() == [2, "forbid"]
    assert r.status_code == 200  # this should be 422 then!

Description

I would like to ensure that the models/queries used in my pytests are up to date with the code. Hence, the goal was to set the Config.extra parameter to "forbid" in the pytests.

Note that the original application requires "ignore" to not break production. So "forbid" should only be used within the tests.

pytest test_fastapi_extra.py
should raise an error but does not... so weirdly enough the model config is set to "forbid" but the extra fields do not cause an unprocessable entity error.

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.74.1

Python Version

3.9.7

Additional Context

pydantic 1.9.0
pytest 7.0.1

[camold]

If ever someone comes accross this problem. The solution was to use the values provided by pydantic.Extra instead of the strings for "forbid" and "ignore". This works as expected.
Unfortunately the documentation in pydantic mentions that you could use either the string or the enum but apparently they are not working the same way.

###### fastapi_extra.py
import fastapi
from pydantic import BaseModel, Extra


class MyModel(BaseModel):
    i: int

    class Config:
        extra = Extra.ignore # use the enum provided by pydantic here instead of "ignore" string


def create_app():

    app = fastapi.FastAPI()

    @app.post("/")
    def test(m: MyModel):
        return [m.i, MyModel.Config.extra]

    return app

########### test_fastapi_extra.py
import pytest
from fastapi.testclient import TestClient
from pydantic import Extra

import fastapi_extra

# overwrite from Extra.ignore to Extra.forbid using the enums again!
fastapi_extra.MyModel.Config.extra = Extra.forbid


@pytest.fixture
def test_app():
    yield TestClient(fastapi_extra.create_app())


def test_root(test_app):
    # send a message with an additional attribute
    r = test_app.post("/", json={"i": 2, "foo": "bar"})
    assert r.status_code == 422
    assert r.json() == {
        "detail": [
            {
                "loc": ["body", "foo"],
                "msg": "extra fields not permitted",
                "type": "value_error.extra",
            }
        ],
    }

[tiangolo]

Thanks for reporting back and closing the issue 👍