[BUG] Request object used in the route is not the same object used for exception handling

[sevakharutyunyan]

Problem

In this discussion we provide the script, requirements, and commands to run and test the app.
We expected to see the same id for both request objects, however they are not the same object. Moreover, both requests share the same state property.

from starlette.applications import Starlette
from starlette.responses import JSONResponse
from starlette.routing import Route
from starlette.requests import Request

from pydantic import BaseModel, ValidationError

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


async def homepage(request: Request):
    print(id(request))
    request_json = await request.json()
    _ = RequestModel(**request_json)
    return JSONResponse({'hello': 'world'})


def bad_request(request: Request, exc: ValidationError):
    print(id(request))
    return JSONResponse(
        content={"error": exc.errors()},
        status_code=400,
    )

exception_handlers = {
    ValidationError: bad_request
}

app = Starlette(
    debug=True, 
    routes=[Route('/', homepage, methods=["POST"])],
    exception_handlers=exception_handlers
)

Requiremets:

uvicorn==0.19.0
starlette==0.22.0

Command:

uvicorn app:app

Test:

curl --request POST \
  --url 'http://localhost:8000/?=' \
  --header 'Content-Type: application/json' \
  --data '{
	"name": 12,
	"age": "Arthur"
}
'

[alex-oleshkevich]

Yes, this is by design. Request class is just an API interface to ASGI scope. If you want to share data, use request.state object.
For example, request.state.request_id = 42.

There is a bunch of issues related to this topic. You can search for them for more information.

[sevakharutyunyan]

Thanks Alex. The reason we created this discussion is that we couldn't find the explanation in documentation explicitly.
https://www.starlette.io/exceptions/