Kotlin compiler generates methods with more than 255 parameters

[sakulisko]

Hello,
if proto message contains more than 255 fields it generates the copy method with the same number of parameters. This will fail in JVM environment because the jvm supports up to 255 parameters https://docs.oracle.com/javase/specs/jvms/se16/html/jvms-4.html#jvms-4.3.3.

The kotlin file looks fine and kotlinc is able to compile *.kt to *.class without any issue. But it's not possible to use *.jar with these *.class files in android project.

The same issue was already resolved for java compiler: #691
Another issue related to high number of fields: #1575

Possible solutions:

• Limit the number of parameters in the same way as for java output and behave in the same way as java_interop = true, when the limit is reached
• Change how the generated message looks like. Use DSL-like syntax instead of named parameters (https://proandroiddev.com/writing-kotlin-dsls-with-nested-builder-pattern-66452476d5ef). This can be controlled by compiler flag to keep backward compatibility

Unfortunately both of the solutions can cause breaking changes in generated *.kt files

[oldergod]

What's causing your proto schema to have that many fields? Do you have a big oneof in there?

[sakulisko]

It's flat structure. The proto is generated from web-ui. No oneof, just message with many fields.

[oldergod]

Unfortunately there is no solution around this for now. The feature we've been working on in #1448 will address very long oneof only.