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https://issues.apache.org/jira/browse/TINKERPOP-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15621705#comment-15621705
]
ASF GitHub Bot commented on TINKERPOP-887:
------------------------------------------
Github user BrynCooke commented on the issue:
https://github.com/apache/tinkerpop/pull/470
The lambda traversal will throw a regular NoSuchElementException is it is
unparented.
However, won't this will only happen once? The exception will bubble up and
out of the top level traversal?
If they did this
```
g.V().blah().map{ x ->
try {
__.inject(x).will().not().have().anything().next()
return "foo";
}
catch(NoSuchElementException e) {
return "bar";
}
}
```
instead of
```
g.V().blah().map{ x ->
if(__.inject(x).will().not().have().anything().hasNext()) {
return "foo";
}
else {
return "bar";
}
}
```
Then they would have a problem.
> FastNoSuchElementException hides stack trace in client code
> -----------------------------------------------------------
>
> Key: TINKERPOP-887
> URL: https://issues.apache.org/jira/browse/TINKERPOP-887
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.0.2-incubating
> Reporter: Bryn Cooke
> Assignee: Marko A. Rodriguez
> Priority: Minor
>
> I wrote some code that incorrectly assumed that a Gremlin query would return
> an element, but it didn't. The surprise was that I got no stack trace and
> therefore had no idea where in *my* code I had introduced the error.
> I haven't looked in detail at the TP code, so what comes next is speculation:
> If FastNoSuchElementException is being used in truly exceptional
> circumstances then why is a singleton is used over a normal exception with
> stack trace? It could just as easily be converted to a normal exception.
> If FastNoSuchElementException is being used for control flow then probably it
> shouldn't. Code should check hasNext rather than trying for next and dealing
> with an exceptional result. I'm not sure what the current state of things are
> in the JVM but at least in the past try catch blocks would inhibit
> optimization even without stack traces so this type of code was considered an
> antipattern.
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