Bug with "Sample" operator in 1.2.4

[kidinov]

Library version 1.2.4.

Bug reporting inspired by that SO question.

Code sample to reproduce:

Observable<String> names = Observable
        .just("Mary", "Patricia", "Linda", "Barbara",
                "Elizabeth", "Jennifer", "Maria", "Susan",
                "Margaret", "Dorothy");
Observable<Long> absoluteDelayMillis = Observable
        .just(0.1, 0.6, 0.9, 1.1,
                3.3, 3.4, 3.5, 3.6,
                4.4, 4.8)
        .map(d -> (long) (d * 1_000));
Observable<String> delayedNames = names
        .zipWith(absoluteDelayMillis,
                (n, d) -> Observable
                        .just(n)
                        .delay(d, TimeUnit.MILLISECONDS))
        .flatMap(o -> o);
delayedNames
        .sample(1, SECONDS)
        .subscribe(System.out::println);

Output:

Linda
Barbara
Susan
Dorothy

But, as far I understand that operator, it should be:

Linda
Barbara
Susan

Because "tick" on 5000 should not happen after onComplete called.

[akarnokd]

This was a requested feature that made it into 1.1.3: Discussion, PR.

The common documentation of sample also indicates emission of the very last event in case of the termination. The RxJava diagram hasn't been updated it seems.

In 2.x, the last element in the internal buffer is not emitted in any of the sample variants.

[akarnokd]

I can add an overload scan(long, TimeUnit, Scheduler, boolean) to emit the very last unsampled value before completing, but it won't get into 2.0.4 as I need to update 2 x 2 operators, plus there is a peculiar race between onComplete() and the sampling run() that needs to be addressed.

[akarnokd]

See #4955 for 2.x and #5007 for 1.x.

[akarnokd]

Closing via #5007.