lift signature issue returns on new typescript version

[ritox842]

On version 5.4.2 there's a bug fix:

Subject: lift signature is now appropriate for stricter TypeScript 2.4 checks (#2722) (9804de7)

I'm using typescript version 2.4.1 and I'm getting this bug again...

What can I do?

[ericeslinger]

yeah, I'm having the same issue - rolling back to typescript@2.4.0 for now.

[kwonoj]

If you're experiencing this still, please provide minial repo have single rxjs dependency can repro this issues.

[ericeslinger]

super-minimal test case here: https://github.com/ericeslinger/lift-example

git clone https://github.com/ericeslinger/lift-example.git
cd lift-example && npm i && npm test

All I really do is implement lift thusly:

export class ExtendedObservable<T> extends Observable<T> {
  lift(operator) {
    const observable = new ExtendedObservable();
    observable.operator = operator;
    return observable;
  }
}

which isn't precisely what I'm doing in my actual work, but seems like a pretty minimal reproduction.

this is confirmed to work when I install typescript@2.4.0 and fail under 2.4.1 (to test in the repo, npm i typescript@2.4.0 && npm test )

[kwonoj]

@ericeslinger your example isn't cases of lib's incorrect type signature, it's expected TS behavior.

Note TS 2.4.1 enables strict generic check, reason why your code works on prior version of compiler. Signature of base lift is lift<R>(operator: Operator<T, R>): Observable<R>, and inherited lift is inferred by compiler as life(operator:any): ExtendedObservable<{}>, so there is type incompatibility occurs.

Correcting it by explicit casting like

lift<T>(operator): Observable<T> {
    const observable = new ExtendedObservable() as Observable<T>;
    (observable as any).operator = operator;
    return observable;
  }

resolves issue. (Note: above snippet is only for illustration)

I'll leave this issue opened bit more to see if there's any remaining issue around library itself - meanwhile, anyone experience similar issues please check 2 things

• Is there any dependency still have old version of Rx in somewhere?
  : you have to physically check node_modules for this. To isolate this, simplest way is create minimal reproducible repo.

• Is this caused by library code?
  : If so, it should happen by using variant of observable inherited object, like Subject. If not, check if user code have compatible types.

[GulinSS]

See #2722 (comment)
Looks like need update .d.ts also

[kwonoj]

@GulinSS d.ts type definition is auto-generated and already updated.

Pleasd check above comment (#2726 (comment)) , and share reproducible repo for code ensure if there is no dupe pkg, or user code has incompatible types.

[GulinSS]

@kwonoj, did deeper investigation, the issue was in ionic-native dep which referenced to older rxjs version

[kwonoj]

as I do not see further report related with library code itself, I'm closing this issue for now. Anyone experiences similar issue and confirmed if it's not coming from old pkg version or user code, feel freely create new issue with reproducible repo.