[10] RFR 8193856 takeWhile produces incorrect result with elements produced by flatMap

[Paul Sandoz]

Hi,

Please review this fix for a bug in the stream takeWhile operation:

  http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/ <http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8193856-takeWhile-incorrect-results/webrev/>

The flatMap operation is currently aggressive and does not detect if a downstream operation may or has cancelled processing, and will push all of it’s elements downstream. Short-circuiting operations should be guarded against such behaviour but unfortunately takeWhile was not guarded.

—

Separately i plan to figure out a way to ensure flatMap operations become less aggressive if there are short-circuiting downstream operations. This may increase efficiency and also allow support for flat map results that are infinite.

Paul.