Is Byte Buddy intended to be used for instrumenting Kotlin code?

[Guillaume Darmont]

Hey everyone!

I'm currently playing with Byte Buddy to instrument a codebase of mixed Java and Kotlin code.
Instrumentation fails on some Kotlin methods or parameters which have names considered by Byte Buddy as not valid.
A reproducer is available here https://github.com/gdarmont/kotlin-byte-buddy-tests

Example of Kotlin parameter names: <set-?>, <unused var>, <destruct>. Left and right angle brackets are part of the name.
These names are clearly not valid in Java, but are valid for the JVM, as specified in https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2.2 

Hence my question in the title, is Byte Buddy bytecode generation meant to be compatible with Java source code only?

Regards,
Guillaume

[Rafael Winterhalter]

It is not, you can disable type validation entirely:

new ByteBuddy().with(Type validation.DISABLED)

By default, Byte Buddy adheres to the spec, but early Kotlin compilers were not compliant. (The reflection API would struggle on those, too)

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[Guillaume Darmont]

Thanks for the answer. Disabling validation will help as a quick workaround for now.

Regarding the specification compliance, validation code for Unqualified Names in BB should be updated, as Kotlin 2.1 generated bytecode is definitely legit regarding the Java Virtual Machine Specification, and in fact, is classloaded and runs without any problems in production.

I may have a look into this if I find some time in the next few days.

Thanks again.

Guillaume

[Rafael Winterhalter]

Thanks, very possible that the check is wrong. It is implemented in InstrumentedType#isValidIdentifier.

If you have time to have a look, I would appreciate it!