Description
Bug Report
Current Behavior
The way the types for 'startWith' are written it only allows adding values of the same type as the underlying observable. However, I am observing a lot of usage where people call start with a value outside the original observable type.
AFAICT, there is not fundamental reason why startWith types are so limiting and they can be written to support more permissive usecases.
Reproduction
https://stackblitz.com/edit/typescript-yhhbxn?file=index.ts
const o$ = of(0,1,2);
let o2$ = o$.pipe(
startWith(null)
)o2$ is of type Observable<number> and there is no error. With --strictFunctionTypes there is a type error.
Expected behavior
o2$ should be of type Observable<number | null>
Environment
- RxJS version: 6.3.2
Possible Solution
Change type of startWith to something like:
startWith<S>(x: S) => (Observable<T> => Observable<T | S>)Additional context/Screenshots
Ngrx users for some reason keeps typing startWith(null) on non-nullable observables.