RxJava: 2.1.2 Completable with andThen never completes

You want andThen(Completable.complete()). Note the use of parenthesis and not curly braces. The latter creates a lambda that doesn’t call its emitter.

On Sat, Aug 12, 2017, 11:30 AM Michał Klimczak notifications@github.com wrote:

This test fails:

Completable.complete() .andThen{ Completable.complete() } .test() .assertComplete()

However this one succeeds:

Completable.complete() .test() .assertComplete()

This one also succeeds:

Flowable.just("")
        .flatMap { Flowable.just("") }
        .test()
        .assertComplete()

My understanding is that concating (which is what andThen does?) two completables which complete immediately should complete. I tried:

• using awaitForTerminalEvent but it just runs forever in the first case.
• .andThen{} instead of .andThen{ Completable.complete() }
• Completable.fromCallable instead of Completable.complete() or switching from a Flowable to Completable

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Please be patient on StackOverflow (deleted) next time!

For one, you implemented Completable incorrectly and in a way most people don’t need to do it. Use Completable.create() instead. Second, you have to complete the CompletableObserver, otherwise andThen won’t know to switch to the other source.

Completable completable = Completable.create(emitter -> {
    emitter.onComplete();
});

completable
        .andThen(observable)
        .subscribe(integer -> System.out.println("emitted:"+integer));

This is a very silly api tbh, everyone I know was burned by this

Generally I am, but it honestly looked like an error to me, especially given the way flatMap and similar operators work for Flowable. Sorry!

@ericntd It’s not an issue with RxJava but how Kotlin trains you to use { } as the convenient lambda syntax. So RxJava 3 can’t help you solve this problem either.

@amanshuraikwar That is how it is supposed to be done. How is it not working. Could you write an unit test demonstrating your problem?

@micHar I agree with you, the .andThen{} is equivalent to .doOnComplete{}, isn’t it? I mean what would be the use case that only .andThen{} solve ?