ProGuard process for Scala runnable JAR

Question

I'm trying to shrink (and also to obfuscate and to optimize) simple Scala program which packed into runnable JAR.

I created 2 projects in Scala IDE: simple Scala program and Java wrapper which executes this Scala program. Then I generated runnable JAR using "Export" -> "Runnable JAR file" Eclipse utility with "Extract required libraries into generated JAR" option.

After that I tried to shrink JAR with ProGuard shrinker (GUI version) but it failed with the following notes and warnings: output at pastebin.com.

Is there any correct way to do this?

Answer 1

A good place to start is with the suggested parameters for running proguard on a scala project at http://proguard.sourceforge.net/manual/examples.html#scala. Those basic options will probably solve most of those warnings, e.g.:

-dontwarn scala.**

-keepclasseswithmembers public class * {
    public static void main(java.lang.String[]);
}

-keep class * implements org.xml.sax.EntityResolver

-keepclassmembers class * {
    ** MODULE$;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinPool {
    long eventCount;
    int  workerCounts;
    int  runControl;
    scala.concurrent.forkjoin.ForkJoinPool$WaitQueueNode syncStack;
    scala.concurrent.forkjoin.ForkJoinPool$WaitQueueNode spareStack;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinWorkerThread {
    int base;
    int sp;
    int runState;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinTask {
    int status;
}

-keepclassmembernames class scala.concurrent.forkjoin.LinkedTransferQueue {
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference head;
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference tail;
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference cleanMe;
}

I also use these:

-keepattributes Signature,*Annotation*
-dontobfuscate

// turn some optimizations off when using -dontobfuscate
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*,!code/allocation/variable,!class/unboxing/enum

// lots of other classes, e.g. logging
-keep public class ch.qos.logback.** { *;}
-keep public class org.slf4j.** { *;}    

If you're looking to automate it, you can also run proguard in sbt with the sbt-proguard plugin. The proguard output can then be fed into sbt-assembly or sbt-native-packager if you want to incorporate it into an executable jar or a package.