Rule proposal for noUselessOptionalChaining and noUselessNonNullAssertion

[MikeRomaa]

I would like to propose two new, related rules for Biome in the "correctness" category. These would both have very simple safe fixes that simply removes the errant operator. Curious to see what others think about these.

If this is something that is desirable in the nursery, I would be interested in implementing myself as I've been long awaiting a chance to contribute to Biome.

noUselessOptionalChaining

Disallow the use of the optional chaining operator (?.) on types that are not unions including undefined or null.

type Range = { start: Date, end?: Date };

const struct: MyType = { start: new Date(), end: new Date() };

const startTimestamp = struct.start?.getTime(); // Invalid since `start` is never `undefined | null`
const endTimestamp = struct.end?.getTime();

noUselessNonNullAssertion

This one is related to noExtraNonNullAssertion.

Disallow the use of the non-null assertion operator (!) on types that may return undefined or null.

function doSomething(element: Element | undefined) {}

const element = document.getElementById("some-id");
// Perhaps the programmer knows the element exists
// Should ideally be done above, but for the sake of example...
doSomething(element!); // Invalid since parameter `element` may be `undefined`

[arendjr]

Thanks for the suggestions! We do usually use #3 for rule suggestions. Could you create a comment there and link to this discussion?

I do like the rule suggestions themselves, but please keep in mind these would rely on the presence of type information. As such, I'm afraid it would be too soon to start implementing them right now, because #3187 would need to be done first.

[MikeRomaa]

I can absolutely do that! Thanks for the comment, I'll keep an eye out for that ticket.