Typing: Add overload to Router.add() for function-style endpoints

[bblommers]

Motivation

One fairly common use case (in my experience) is to use a regular function as an endpoint, i.e.:

ROUTER.add(
    path="/<path:path>",
    methods=["PUT"],
    endpoint=self.my_func,
)

def my_func(self, request: Request, path: str) -> Response:
    return Response(status=200, response=b"..")

Running MyPy on this currently throws an error:

error: No overload variant of "add" of "Router" matches argument types "str", "list[str]", "Callable[[Request, str, str, str, str], Response]"  [call-overload]
note: Possible overload variants:
note:     def add(self, path: str, endpoint: Handler, host: str | None = ..., methods: Iterable[str] | None = ..., **kwargs: Any) -> Rule
note:     def add(self, fn: _RouteEndpoint) -> list[Rule]
note:     def add(self, rule_factory: RuleFactory) -> list[Rule]
note:     def add(self, obj: Any) -> list[Rule]
note:     def add(self, routes: list[_RouteEndpoint | RuleFactory | Any]) -> list[Rule]

Adding this overload solves the problem, and removes the need to add type: ignore's all over the place

[bblommers]

I've copied the entire docstring from the previous overload, including the TODO - I only changed the description of the endpoint-argument. Happy to adjust this!

[thrau]

nice thanks for adding this! i haven't thought about mypy too much, i should do more with it!

[bblommers]

i haven't thought about mypy too much, i should do more with it!

Absolutely! It can be a pain to introduce to an existing codebase, but considering how much (potential) bugs it can catch, definitely worth it 🙂