Kotlin static methods not recognized after Proguard/R8 minimization?

Question

I'm using R8 to minimize my library, and the companion object's methods aren't being picked up as references of the main class. The companion and the methods still exist, I just can't call them without referencing the companion object.

// Works
MyClass.Companion.foo()

// Errors with an unresolved reference.
MyClass.foo(this)

My proguard rules:

-keep @interface kotlin.Metadata { *; }
-keepattributes RuntimeVisibleAnnotations

-keep public class com.example.MyClass {
    public <methods>;
    public static <methods>;
}
-keep public class com.example.MyClass$Companion {
    public <methods>;
}

The companion methods are also labeled @JvmStatic, and those static methods exist in the generated code, but the kotlin compiler doesn't recognize those either.

Answer 1

This is due to your models getting obfuscated when minify is enabled. To fix add the path to your models package to your Proguard rules.

Something like this should work:

-keep class your.package.name.model.** { *; } //remember to modify this
-keepattributes Signature
-keepattributes *Annotation*
-keep class * implements java.io.Serializable {
    static final long serialVersionUID;
    private static final java.io.ObjectStreamField[] serialPersistentFields;
    private void writeObject(java.io.ObjectOutputStream);
    private void readObject(java.io.ObjectInputStream);
    private void readObjectNoData();
    Object writeReplace();
    Object readResolve();
}