[jira] [Comment Edited] (LUCENE-7800) Remove code that potentially rethrows checked exceptions from methods that don't declare them ("sneaky throw" hack)

["Dawid Weiss (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-7800?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15980321#comment-15980321 ] 

Dawid Weiss edited comment on LUCENE-7800 at 4/23/17 8:28 AM:
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bq. The MethodHandles called there are known to not throw unexpected Exceptions!

See my example in https://issues.apache.org/jira/browse/LUCENE-7796?focusedCommentId=15980320 - there's definitely a way to propagate an unchecked exception up the caller stack. To me this is surprising and is a low-level hack that really has little motivation. We could replace it with a dedicated (unchecked) exception wrapper, but just letting a checked exception propagate up the stack seems like the wrong way to go.


was (Author: dweiss):
bq. The MethodHandles called there are known to not throw unexpected Exceptions!

See my example in https://issues.apache.org/jira/browse/LUCENE-7796?focusedCommentId=15980320 - there's definitely a way to propagate an unchecked exception up the caller stack. To me this is surprising and is a low-level hack that really has little motivation. We could replace it with a dedicated (unchecked) exception wrapper, but just letting an unchecked exception propagate up the stack seems like the wrong way to go.

> Remove code that potentially rethrows checked exceptions from methods that don't declare them ("sneaky throw" hack)
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-7800
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7800
>             Project: Lucene - Core
>          Issue Type: Task
>            Reporter: Dawid Weiss
>            Priority: Minor
>             Fix For: 6.x, master (7.0)
>
>         Attachments: LUCENE-7800.patch
>
>
> For a long time I considered the "sneaky" throw hack to be a nice way of coding around some of Java's limitations (especially with invoking methods via reflection or method handles), but with time I started to see how it can be potentially dangerous and is nearly always confusing. If you have a Java method and its signature doesn't indicate the possibility of a checked exception you, as a programmer, simply don't expect it to happen. Never. So, for example, you could write:
> {code}
> try {
>  luceneApi();
> } catch (RuntimeException | Error e) {
>   // Handle unchecked exceptions here.
> }
> {code}
> and consider the code above to be absolutely bullet-proof in terms of handling exceptions. Unfortunately with sneaky throws anywhere in the "luceneApi" this is no longer the case -- you can receive a checked exception that will simply fall through and hit some code frame above.
> So I suggest we remove sneaky throw from the core entirely. It only exists in two places -- private methods inside Snowball programs invoked via method handles (these don't even declare checked exceptions so I assume they can't occur) and AttributeFactory -- here there is a real possibility somebody could declare an attribute class's constructor that does throw an unchecked exception. In that case I think it is more reasonable to wrap it in a RuntimeException than rethrow it as original.
> Alternatively, we can modify the signature of {{createAttributeInstance}} and {{getStaticImplementation}} to declare some kind of checked exception (either a wrapper or even a Throwable), but I see little reason for it and it'd change the API.



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