Paginator hasNext() works incorrectly on small results

While working with the Paginator in our QA system I traced down a bug that will only happen when the page size is greater than the number of items in the underlying view/query. We wanted to call hasNext() multiple times because one layer of code validates that it has a good Paginator (due to other problems we were having with our cluster). However, because the actual response is fetched during hasNext(), and because the FINISHED state is set as a result of that, only the first hasNext() will return true even though we have not retrieved the response with next() yet.

For example, we should be able to call, hasNext() multiple times, and then state is only changed to indicate FINISHED after we actually retrieve the response using next().

After tracing this bug down, I can see that hasNext() returns false right away if FINISHED is true, and I can see that the FINISHED state is set during the fetch that happens during hasNext(). So when there is less than one page of data available, the first hasNext() will return true, and the next hasNext() will return false, which is a problem if the consumer has not actually called next() to fetch the response.

I think the simple fix here is to only set the FINISHED state in next() so you know that the data has actually been retrieved by the consumer. That way the consumer is free to ask hasNext() as many times as required for their logic, and it will not effect internal state until next() is called.