🔒 Exclude FastApi DI Attribute from Excpected Request Body

[radiant vapor]

@router.post("/mails", tags=["mails"])
async def send_mail(
    payload: PostMailsRequest,
    rabbitmq: Annotated[RabbitMQ, Depends()],
) -> Response:
    ...

rabbitmq is injected like this: app.dependency_overrides[RabbitMQ] = lambda: rabbitmq

Now my request body is:

{
  "payload": {
    ...
  },
  "config": {
    ...
  }
}

What I actually want is just (which happens when I remove rabbitmq: Annotated[RabbitMQ, Depends()],:

{
 # payload data
}

[grave fox]

@radiant vapor

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[frank blaze]

Can you share your request model? Is RabbitMQ your own class?

[radiant vapor]

Yes, RabbitMQ is my own class

class PostMailsRequest(BaseModel):
    """Model for sending email requests."""

    subject: str
    body: str
    recipient_email: EmailStr

[frank blaze]

And how does RabbitMQ look?

[radiant vapor]

https://pastebin.com/GVfe811Q

[frank blaze]

I'm thinking fastapi doesn't look at override annotations for validation

[radiant vapor]

but rabbitmq should not included at all in the request body, it should just be provided y dependency injection

[frank blaze]

So you should use a getter function

FastAPI is ignoring the overrides for validation

It looks at the RabbitMQ constructor and seeing it needs config

[radiant vapor]

like this?

def get_rabbitmq() -> RabbitMQ:
    ..

@router.post("/mails", tags=["mails"])
async def send_mail(
    payload: PostMailsRequest,
    rabbitmq: RabbitMQ = Depends(get_rabbitmq),

[frank blaze]

Yes

[dapper tapir]

yes this will call and get the obj

[radiant vapor]

well that works for excluding it from the request but the my config should be provided on startup

rabbitmq = RabbitMQ(config)

app = FastAPI()
app.dependency_overrides[RabbitMQ] = lambda: rabbitmq

[frank blaze]

If you init RabbitMQ during startup, you can yield a dict in the lifespan function for request.state

[dapper tapir]

if config never changes you can place it in app.lifespan

[radiant vapor]

so that would be smth like this?

# startup
app.state.rabbitmq = RabbitMQ(config)

# router
async def get_rabbitmq(request: Request) -> RabbitMQ:
    return request.state.rabbitmq

I think that's a solution but a bit unfortunate that I can't do it with the override and as attr rabbitmq: Annotated[RabbitMQ, Depends()], would have been cleaner

[frank blaze]

Make a wrapper class for it

[dapper tapir]

you can do it like this also

rabbitmq: Annotated[RabbitMQ, Depends(get_rabbit)]

[frank blaze]

class Rabbit:
  def __init__(self, request: Request):
    self.rabbit = request.state.rabbitmq

[radiant vapor]

I still would need to write the get_rabbit mq class and get it from the manager which is also not typed

Gimme a couple of minutes I will try that

[frank blaze]

Call it RabbitService and include functions that wrap RabbitMQ

[radiant vapor]

hmmm, this gives me an AttributeError: 'State' object has no attribute 'rabbitmq'

app = FastAPI()
app.state.rabbitmq = rabbitmq

app.include_router(users.router)
app.include_router(mails.router)

app.middleware("http")(logging_mw)

class RabbitService:
    def __init__(self, request: Request) -> None:
        self.rabbit = request.state.rabbitmq

@router.post("/mails", tags=["mails"])
async def send_mail(
    payload: PostMailsRequest,
    rabbit_service: Annotated[RabbitService, Depends(RabbitService)],
) -> Response:
    """Send a mail."""
    triggered_event = MailTriggeredEvent(
        subject=payload.subject,
        body=payload.body,
        recipient_email=payload.recipient_email,
    )
    rabbit_service.rabbit.publish(triggered_event)
    return Response(status_code=status.HTTP_200_OK)

[radiant vapor]

this app.state.rabbitmq = rabbitmq doesn't seem to do the trick, it has to be in the startup event?

[frank blaze]

You need to use app lifespan

[radiant vapor]

@asynccontextmanager
async def lifespan(app: FastAPI):
    app.state.rabbitmq = rabbitmq
    yield

app = FastAPI(lifespan=lifespan)

doesn't do the trick

[frank blaze]

import contextlib
from fastapi import FastAPI

config = Config()
rabbitmq = RabbitMQ(config)

@contextlib.asynccontextmanager
async def lifespan(app: FastAPI):
  yield {
    "config": config,
    "rabbitmq": rabbitmq,
  }

app = FastAPI(lifespan=lifespan)

[radiant vapor]

okay that works, interesting how they implemented that.

[radiant vapor]

Is that how "di" usually should implemented with fastapi?

[frank blaze]

This is unrelated to di

This is initializing state during lifespan

[radiant vapor]

Yeah your right I understand that, but essentially what I wanted was "DI" for a service that depended on a config. I was more wondering if this is the common way to do this?

I haven't spent much time with python / fastapi yet so I'm wondering if what I'm doing maybe is not the common way how things are done in python

[radiant vapor]

!close

[grave fox]

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