readBody has a default returnType of Promise<any> instead of Promise<unknown>

[rijkvanzanten]

Environment

Node v20.2.0
h3 1.6.6
typescript 5.0.4

Reproduction

import { eventHandler, readBody, sendNoContent } from "h3";

export const routeExample = eventHandler(async (event) => {
	const body = await readBody(event);
	// => const body: any
});

Describe the bug

When using readBody, the output type is typed as Promise<any>. This in turn means it's very easy to accidentally lose type safety from the response body, as TypeScript will treat any use of the response as valid (where it's most likely not going to be). By returning Promise<unknown> instead, h3 can explicitly communicate that the return type should be handled with care, instead of treating every use of it as valid. You can find a super basic example of the type of any "trap" in this playground: https://www.typescriptlang.org/play?#code/MYewdgzgLgBAhgEwQFQO4hgXhgCjAVwFsAuGAwgIwFMAnASiwD4yiYBqGAJgG4BYAKAGhIsCiAQBPAIJgJpOLKwwARAAsqAGw0Z0NDQmV9+w6DDGSAqmADWYEKjCl8Nuw6VrN2mLv2GBAxBR0HHNpWTojQLQQEPEJK1t7MAigA. Note how the unknown body use throws a helpful error in this mistaken usage example.

Additional context

You can workaround the problem by providing the explicit type you expect in the override:

interface BodySchema {
  action: 'comment';
  message: string;
}

await readBody<BodySchema>(event);

or manually set unknown if you can't rely on the input body:

await readBody<unknown>(event);

Logs

No response

[pi0]

Fixed by #791 for h3 v2 (coming!)