[2.1.0] buffer(timespan, unit, count) emits duplicated items

[loneid]

The following code:

import io.reactivex.Observable;
import org.junit.Test;

import java.util.concurrent.TimeUnit;

public class BufferTest {
    @Test
    public void testBuffer() {
        Observable.range(0, 10)
                .map(n -> {
                    Thread.sleep(100);
                    return n;
                })
                .buffer(1, TimeUnit.SECONDS, 5)
                .subscribe(System.out::println);
    }
}

is expected to print something like:
[0, 1, 2, 3, 4]
[5, 6, 7, 8]
[9]

but try to run it several times and you can see that sometimes it prints out:
[0, 1, 2, 3, 4]
[5, 6, 7, 8, 9]
[5, 6, 7, 8, 9]
[]
where one of the bunches is duplicated.

[akarnokd]

Thanks for reporting. This is a bug in both Observable and Flowable operators. I'll post a fix shortly.

[akarnokd]

Closing via #5427.