RFR: 8331987: Enhance stacktrace clarity for CompletableFuture CancellationException

[Doug Lea]

On Mon, 13 May 2024 17:06:10 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> This change adds wrapping of the CancellationException produced by CompletableFuture::get() and CompletableFuture::join() to add more diagnostic information and align better with FutureTask.
>> 
>> Running the sample code from the JBS issue in JShell will produce the following:
>> 
>> 
>> jshell> java.util.concurrent.CancellationException: 
>> 	at java.base/java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:392)
>> 	at java.base/java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2073)
>> 	at REPL.$JShell$18.m2($JShell$18.java:10)
>> 	at REPL.$JShell$17.m1($JShell$17.java:8)
>> 	at REPL.$JShell$16B.lambda$main$0($JShell$16B.java:8)
>> 	at java.base/java.lang.Thread.run(Thread.java:1575)
>> Caused by: java.util.concurrent.CancellationException
>> 	at java.base/java.util.concurrent.CompletableFuture.cancel(CompletableFuture.java:2510)
>> 	at REPL.$JShell$16B.lambda$main$1($JShell$16B.java:11)
>> 	... 1 more
>
> src/java.base/share/classes/java/util/concurrent/CompletableFuture.java line 392:
> 
>> 390:                 return null;
>> 391:             if (x instanceof CancellationException)
>> 392:                 throw new CancellationException("", (CancellationException)x);
> 
> One option here would be to put "CompletableFuture.get()" or "get()" as a message.

Given the serviceability motivation, the overkill of adding "get" and "join" strings seems reasonable.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19219#discussion_r1598868469