Add generics to get/query methods

Describe the feature you’d like:

I know the element type I’m querying, so it’d be beneficial to specify it upfront:

screen.queryByText<HTMLButtonElement>('click me'); // -> HTMLButtonElement | null

Type assertions are very error prone, so should be avoided:

screen.queryByText('click me') as HTMLButtonElement; // can still be null!

Suggested implementation:

queryByText<T extends HTMLElement = HTMLElement>(...) => T | null;

Describe alternatives you’ve considered:

You can do already do something similar with for example querySelector:

document.body.querySelector<HTMLButtonElement>('.my-button');

Teachability, Documentation, Adoption, Migration Strategy:

[eps1lon]

~Definitely going to strongly advocate for type casting here. More explanation in https://twitter.com/SeaRyanC/status/1090998621472940032~

~TL;DR: Using generics in this case is just like type casting without the explicitness of type casting which makes it strictly worse.~

Update: See https://github.com/testing-library/dom-testing-library/issues/615#issuecomment-655411294 for current opinion.

[eps1lon]

@timdeschryver A role="button" can be any Element not just HTMLButtonElement. Same applies to most roles.