Inconsistent add_api_route types

[Kludex]

Discussed in #10235

^{Originally posted by sidekick-eimantas September 12, 2023}

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Example Code

### Direct mounting of routes
import pathlib

from fastapi import FastAPI, APIRouter
import uvicorn
import pydantic

class HelloRequest(pydantic.BaseModel):
    id: str


class HelloResponse(pydantic.BaseModel):
    hello: str


class Hello:
    def __init__(self, name: str) -> None:
        self.name = name

    async def handle(self, request: HelloRequest) -> HelloResponse:
        return HelloResponse(hello=self.name)

app = FastAPI()
hello_handler = Hello(name="test")
app.add_api_route("/hello", hello_handler.handle, methods=["POST"])






### Mounting of paths via Router
import pathlib

from fastapi import FastAPI, APIRouter
import uvicorn
import pydantic

class HelloRequest(pydantic.BaseModel):
    id: str


class HelloResponse(pydantic.BaseModel):
    hello: str


class Hello:
    def __init__(self, name: str) -> None:
        self.name = name

    async def handle(self, request: HelloRequest) -> HelloResponse:
        return HelloResponse(hello=self.name)


class RootRouter:
    def __init__(self, name: str):
        self.router = APIRouter()
        hello_handler = Hello(name=name)
        self.router.add_api_route("/hello", hello_handler.handle, methods=["POST"])


app = FastAPI()
root_router = RootRouter(name="test")
app.include_router(root_router.router)

Description

First example produces a mypy error:

error: Argument 2 to "add_api_route" of "FastAPI" has incompatible type "Callable[[HelloRequest], Coroutine[Any, Any, HelloResponse]]"; expected "Callable[..., Coroutine[Any, Any, Response]]"  [arg-type]

Second example does not.

The types of endpoint parameter in FastAPI.add_api_route and APIRouter.add_api_route are inconsistent.

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.103.1

Pydantic Version

2.3.0

Python Version

3.10.7

Additional Context

No response

[Kludex]

This is a valid issue. The type hint of both endpoint parameters should match.

Should be easy to fix - I don't know which one @tiangolo wants.

[annis-souames]

Hey @Kludex

I want to help on this issue if no one is interested, I have used FastAPI before in some hobby projects but this is my first OSS contribution!

[ordinary-jamie]

I'll take this if no one else is!

I don't know which one tiangolo wants.

I would think Callable[..., Any] is preferred:

• FastAPI.add_api_route makes a direct call to APIRouter.add_api_route anyways
• fastapi.dependencies.utils.get_typed_return_annotation has signature def get_typed_return_annotation(call: Callable[..., Any]) -> Any:
• A lot of other functions with similar parameters use the same typing (e.g. FastAPI.add_api_websocket_route)
• The api router instantiates route_class: Type[APIRoute] of which fastapi.routing.APIRoute subclasses starlette.routing.Route which also types endpoint with Callable[..., typing.Any]

Happy to work with either

[Alshymy22]

Direct mounting of routes

import pathlib

from fastapi import FastAPI, APIRouter
import uvicorn
import pydantic

class HelloRequest(pydantic.BaseModel):
id: str

class HelloResponse(pydantic.BaseModel):
hello: str

class Hello:
def init(self, name: str) -> None:
self.name = name

async def handle(self, request: HelloRequest) -> HelloResponse:
    return HelloResponse(hello=self.name)

app = FastAPI()
hello_handler = Hello(name="test")
app.add_api_route("/hello", hello_handler.handle, methods=["POST"])

Mounting of paths via Router

import pathlib

from fastapi import FastAPI, APIRouter
import uvicorn
import pydantic

class HelloRequest(pydantic.BaseModel):
id: str

class HelloResponse(pydantic.BaseModel):
hello: str

class Hello:
def init(self, name: str) -> None:
self.name = name

async def handle(self, request: HelloRequest) -> HelloResponse:
    return HelloResponse(hello=self.name)

class RootRouter:
def init(self, name: str):
self.router = APIRouter()
hello_handler = Hello(name=name)
self.router.add_api_route("/hello", hello_handler.handle, methods=["POST"])

app = FastAPI()
root_router = RootRouter(name="test")
app.include_router(root_router.router

[eydenbarboza]

hi @Kludex Is this still a valid issue? I want to help on this issue if no one is interested

[devkan]

Hi.. is closed? I like FastAPI and want to contribute..

[eydenbarboza]

Hi, this issue is closed ?