Why does litestar need to manually register the route handlers

[duohelingdukele]

from litestar import Litestar, get


@get("/")
async def index() -> str:
    return "Hello, world!"


@get("/books/{book_id:int}")
async def get_book(book_id: int) -> dict[str, int]:
    return {"book_id": book_id}


app = Litestar([index, get_book])

Litestar requires manually passing in a handler list parameter. But other frameworks automatically register handlers when decorators declare routing paths.

from fastapi import FastAPI

app = FastAPI()


@app.get("/users/me")
async def read_user_me():
    return {"user_id": "the current user"}


@app.get("/users/{user_id}")
async def read_user(user_id: str):
    return {"user_id": user_id}

[provinzkraut]

There is a difference here;

In the FastAPI version, you need access to the app object (or a router) which you can register your routes on. This makes building larger / complex applications more difficult, as it requires the entity at the bottom of the hierarchy chain (the route) to know about objects higher in the chain (the app / router).

Litestar's approach encourages decoupling and modularisation. For example, it's very easy to re-use route handler objects:

@get("/")
async def some_handler() -> None:
 ...

v1_router = Router("/v1", [some_handler])
v2_router = Router("/v2", [some_handler])

It also enables a truly stateless and modular approach:

# app/some_module.py
@get("/")
async def some_handler() -> None:
    ...


def create_some_router(base_path: str, guards: list[Guard]) -> Router:
    return Router(base_path, [some_handler], guards=guards)
 

# app/app.py
def create_app(debug: bool) -> Litestar:
    some_guards = []
    if debug:
        some_guards.append(require_authenticated)
 
    return Litestar([create_some_router("/v1", guards=some_guards),])

I wouldn't say that you need to manually register things in Litestar, I'd say that Litestar allows you to be more flexible and explicit.