How to add a custom decorator to a FastAPI route?

Question

How can I add any decorators to FastAPI endpoints?

As you said, you need to use @functools.wraps(...)–(PyDoc) decorator as,

from functools import wraps

from fastapi import FastAPI
from pydantic import BaseModel


class SampleModel(BaseModel):
    name: str
    age: int


app = FastAPI()


def auth_required(func):
    @wraps(func)
    async def wrapper(*args, **kwargs):
        return await func(*args, **kwargs)

    return wrapper


@app.post("https://stackoverflow.com/")
@auth_required # Custom decorator
async def root(payload: SampleModel):
    return {"message": "Hello World", "payload": payload}

The main caveat of this method is that you can’t access the request object in the wrapper and I assume it is your primary intention.

If you need to access the request, you must add the argument to the router function as,

from fastapi import Request


@app.post("https://stackoverflow.com/")
@auth_required  # Custom decorator
async def root(request: Request, payload: SampleModel):
    return {"message": "Hello World", "payload": payload}

I am not sure what’s wrong with the FastAPI middleware, after all, the @app.middleware(...) is also a decorator.

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