Support functional updates for derived atoms

Currently, setters of derived atoms do not support functional updates.

Proposed API:

const listAtom = atom([]);
const sortedListAtom = atom((get) => get(listAtom), (_get, set, update) => set(listAtom, update));

const App = () => {
	const [list, setList] = useAtom(sortedListAtom);
	return <button onClick={() => setList((prev) => [...prev, "oi!"])}>add</button>
};

In other words, is there a reason why the setter of derived atom isn’t a SetStateAction same as for primitive atoms?

[dwelle]

Ok, I understand why — the setter of the derived atom is basically a reducer, and as such you don’t want to prescribe what the update value is (same as useReducer). So this is a pickle.

[dai-shi]

Yeah, for non-TS usage, we’d need to make the atom name descriptive, for example. Closing this as resolved.