I am currently facing the issue that sesions are not persisted correctly and that setting the persistence mode is throwing an exception. Since I am using AngularFire, I have created an issue over there (angular/angularfire#3340).
However, it's possible that this issue is not related to AngularFire but rather with the Firebase JS SDK.
If I'm importing directly from @firebase/auth, fetch the Auth instance and run the native setPersistence() method I'm getting the same exception:
import {setPersistence, getAuth} from "@firebase/auth";
// ..
const auth = getAuth();
if(!auth) {
throw "Umm...";
}
setPersistence(auth, {type: "LOCAL"}).then();
ERROR Error: Uncaught (in promise): Error: INTERNAL ASSERTION FAILED: Expected a class definition
Error: INTERNAL ASSERTION FAILED: Expected a class definition
at debugFail (index-3363a72a.js:497:11)
at debugAssert (index-3363a72a.js:508:9)
at _getInstance (index-3363a72a.js:530:5)
at index-3363a72a.js:2461:59