Summary

As posted on Discord, I was surprised to realize that the return type annotation is not validated; e.g. this doesn't raise an error:

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

The reason is that this should be enforced by a static type checker; runtime validation can be costly. However in general there are several ways for static type checkers to miss finding such errors (Any, cast, # type: ignore, untyped 3rd party libraries, etc) so it would be nice if there was an optional (off by default) parameter (say, validate_response=True) for the user to trade off performance for type safety.

Potential API:

@get("/", validate_response=True)
async def hello_world() -> float:
    return "Hello, world!" 

As for other such parameters, this should be applicable to all layers of an application (handlers, controllers, routers, application object).

Basic Example

No response

Drawbacks and Impact

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Unresolved questions

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