LambdaObserver fails to push exception to error channel and fails with NPE about rxjava HOT 4 CLOSED

If you implement Observables like this, you have to follow the protocol, i.e., call onSubscribe with a Subscription before calling onNext.

However, this is an advanced use case and not recommended in most cases. You haven't shown what readItemPublisher does but you could probably get by with simply using Observable.create.

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It can only happen if onSubscribe was not called, which is a protocol violation.

How are you using the LambdaObserver?

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@akarnokd This is how I am using it. I am not touching any internal classes, I got to it by debugging.

And whenever an error is thrown from any subscriber created with a lambda (I guess this is why a LambdaObservable is created) I get a NPE instead of the actual error itself.

So the general case should be I have an observable. I subscribe to it and in the onNext handler an error is thrown, instead of getting the error on the onError channel it blows up in the try-catch with NPE. Do you still think I am using it wrong because I don't see how.

EDIT: I saw your answer here after this post: #7721 (comment)
EDIT 2: I am continuing the discussion on the issue

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Thank you very much! Using Observable.create instead of fromPublisher really does the trick (in my head I needed a Publisher to push values so I went for it instead of Observable.create which receives an ObservableOnSubscribe as parameter which is what I actually need anyway probably)

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