Is this actually a thing?

The OP had a specific requirement to not obfuscate data classes at all. To whitelist them in one batch, like

data class

is a type or something. Do you have similar restrictions?

I don't have any restriction. My app is just crashing when trying to cast a Data Class to itself. Randomly crashes

I think theres an alternative to proguard that works better

what does “randomly crashes” mean? is it a new exception each time? is it in a new line of the code each time? you should make a Stack Overflow post I think also, the alternative to Proguard from Google that perhaps Dico was referring to is called R8 (but I don’t have any info to know that its better for Kotlin or not)

I’m new to Android but I’ve used ProGuard before back in the J2ME days circa 2003. It’s a mature well tested project, and as far as I know it operates directly on bytecode. I’d be surprised if it contains fundamental bugs of this sort. However, I don’t know how Kotlin maps things like data classes into Java bytecode so I’m not saying it’s definitely not an issue. I’d write a minimal example to see if it’s reproducible. Doing this might help you realise an issue on your side (or prove that it’s a bug).

The random crashes is that the same line of code (a cast of a Sealed class to a Data Class that inherits it) works, unless it's an OnRestoreInstance, in which Proguard screws up and I get a class cast exception (something like

a.b.c$a

cannot be cast to

a.b.c$b

. If I add

@Keep

to the data class, it works

maybe check the proguard mapping file to see what the classes are you can also decompile to see the code where it happens

I'm using `data class`es with Proguard and don't see any problems in production.