from pydantic import BaseModel


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None


app = FastAPI()


@app.post("/items/")
async def create_item(item: Item):
    item_dict = item.model_dump()
    if item.tax is not None:
        price_with_tax = item.price + item.tax
        item_dict.update({"price_with_tax": price_with_tax})

    assert response.json() == {
        "detail": [
            {
                "type": "missing",
                "loc": ["body", "p"],
                "msg": "Field required",
                "input": None,
            }
        ]
    }


@pytest.mark.parametrize(
    "path",
    [
        "/required-bytes",
        "/required-uploadfile",
    ],
)
def test_required(path: str):

# Without aliases


@app.get("/optional-str")
async def read_optional_str(p: Annotated[Optional[str], Header()] = None):
    return {"p": p}


class HeaderModelOptionalStr(BaseModel):
    p: Optional[str] = None


@app.get("/model-optional-str")
async def read_model_optional_str(p: Annotated[HeaderModelOptionalStr, Header()]):
    return {"p": p.p}

def gen_dependency(value: str) -> Generator[str, None, None]:
    yield value


async def async_gen_dependency(value: str) -> AsyncGenerator[str, None]:
    yield value


class CallableDependency:
    def __call__(self, value: str) -> str:
        return value


class CallableGenDependency:
    def __call__(self, value: str) -> Generator[str, None, None]:
        yield value

                "loc": ["body", "grant_type"],
                "msg": "Field required",
                "input": None,
            },
            {
                "type": "missing",
                "loc": ["body", "username"],
                "msg": "Field required",
                "input": None,
            },
            {
                "type": "missing",
                "loc": ["body", "password"],

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Union[int, None] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    age: Union[int, None] = Field(default=None, index=True)
    secret_name: str


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

            "price": 50.5,
            "description": None,
            "tax": None,
        },
    }


def test_post_no_body(client: TestClient):
    response = client.put("/items/5", json=None)
    assert response.status_code == 422
    assert response.json() == {
        "detail": [
            {
                "input": None,
                "loc": [
                    "body",

@app.get("/")
async def get():
    return HTMLResponse(html)


async def get_cookie_or_token(
    websocket: WebSocket,
    session: Annotated[str | None, Cookie()] = None,
    token: Annotated[str | None, Query()] = None,
):
    if session is None and token is None:
        raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
    return session or token


@app.websocket("/items/{item_id}/ws")

    websocket: WebSocket,
    session: str | None = Cookie(default=None),
    token: str | None = Query(default=None),
):
    if session is None and token is None:
        raise WebSocketException(code=status.WS_1008_POLICY_VIOLATION)
    return session or token


@app.websocket("/items/{item_id}/ws")
async def websocket_endpoint(
    websocket: WebSocket,
    item_id: str,
    q: int | None = None,

Le paramètre de requête `q` a pour type `Union[str, None]` (ou `str | None` en Python 3.10), signifiant qu'il est de type `str` mais pourrait aussi être égal à `None`, et bien sûr, la valeur par défaut est `None`, donc **FastAPI** saura qu'il n'est pas requis.

/// note

**FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `= None`.