[eregon]

• The stacktrace is not very useful and is very expensive, for example for Regexp#to_s on a Regexp like /(?i:a)|(?i:b)/.
• On ruby-bench's railsbench it accounts for about 8% of the request time (when run on TruffleRuby).
• Rails master has been improved to use #source instead, Use Regexp#source instead of Regexp#to_s to detect deep filters rails/rails#58678, but that doesn't affect existing releases.

cc @headius

[headius]

I am reluctant to remove the stack trace here. As with other potentially-useful stack traces in JRuby (EAGAIN etc), it could be tied to a property check so it can be enabled if needed. Alternatively, since your use case is to use the compilation as a verification step, we could add an API that allows compilation to report an error condition more cheaply than raising an exception.

[eregon]

My thinking is the Java stracktrace would never be useful to a user of JRuby or TruffleRuby (only the Ruby backtrace).
At most it would be useful to debug a JOni issue, but then running the reproducer under a debugger would provide far more than the stacktrace, so IOW I don't see the value of keeping that Java stacktrace.

What do you think, does that make sense?

A system property default no-stacktrace sounds OK, I can do that if you prefer that.

This change would make every interaction with JOni which ends up in an exception significantly faster, as said above this accounted for 8% of a Rails request, which is very expensive.

[headius]

What do you think, does that make sense?

JOni has consumers other than JRuby and TruffleRuby. I do not know what their expectations are regarding compilation exceptions and stack traces.

A system property default no-stacktrace sounds OK

It's perhaps less ideal than providing a "trial compilation" or syntax-checking path that doesn't trigger exceptions, but it's the simpler fix to just disable the stack trace and make it configurable. Use property org.joni.enableStackTrace.

I wish the JVM was better about omitting stack traces for transient throw (this is a perfect case) but alas, here we are.

this accounted for 8% of a Rails request

It appears JRuby also does such a "trial compilation". The Rails patch is good (simplifies stringification of the Regexp) but I agree that a change here is appropriate for unpatched releases.

[eregon]

PR updated, the stacktrace is now omitted, unless -Dorg.joni.enableStackTrace=true.

[headius]

I'll put it a release later this evening. Thanks!