Kotlin Metadata issue

I have used jackson-module-kotlin successfully in my debug build but can’t get it working on release build with Proguard on. First I added this line to my proguard-rules.pro:

• dontwarn kotlin.**

The App crashes when trying to deserialize first Kotlin class. com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance ofMyKotlinClass (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)

Did some research and found out that I also need to add the following:

• keep class kotlin.Metadata { *; }

The outcome is that app crashes immediately when launched. java.lang.ExceptionInInitializerError at kotlin.h.b.a.b.a.b.<clinit>(Unknown Source) at kotlin.h.b.a.b.a.i.b(Unknown Source) at kotlin.h.b.a.b.g.b.<init>(Unknown Source) at kotlin.h.b.a.b.g.b.<init>(Unknown Source) at kotlin.h.b.a.ac.a(Unknown Source) at kotlin.h.b.a.m$b$a.A_(Unknown Source) at kotlin.h.b.a.ad$a.a(Unknown Source) at kotlin.h.b.a.m$b.e(Unknown Source) at kotlin.h.b.a.j$a$i.A_(Unknown Source) at kotlin.h.b.a.ad$a.a(Unknown Source) at kotlin.h.b.a.j$a.a(Unknown Source) at kotlin.h.b.a.j.g(Unknown Source) at kotlin.h.b.a.j.b(Unknown Source) at kotlin.h.b.a.j$a$e.A_(Unknown Source) at kotlin.h.b.a.ad$a.a(Unknown Source) at kotlin.h.b.a.j.e(Unknown Source) at kotlin.h.b.b.a(Unknown Source) at com.fasterxml.jackson.module.kotlin.KotlinNamesAnnotationIntrospector.findKotlinParameterName(Unknown Source) at com.fasterxml.jackson.module.kotlin.KotlinNamesAnnotationIntrospector.findImplicitPropertyName(Unknown Source) at com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair.findImplicitPropertyName(Unknown Source)

I do get the following warning when building app/build/intermediates/transforms/proguard/release/0.jar Type org.w3c.dom.bootstrap.DOMImplementationRegistrywas not found, it is required for default or static interface methods desugaring ofvoid com.fasterxml.jackson.databind.ext.DOMSerializer.()|   Typeorg.conscrypt.Conscryptwas not found, it is required for default or static interface methods desugaring ofd.a.g.f d.a.g.b.b()

My development environment is Android Studio 3.1.2 Build #AI-173.4720617, built on April 14, 2018 JRE: 1.8.0_152-release-1024-b01 x86_64 JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o Mac OS X 10.12.4

[pmellaaho]

Seems like the following is also very much needed in proguard-rules: -keep class kotlin.reflect.** { *; }

Maybe this could mentioned in the front page “Caveats” -chapter.

[6bangs]

I just ran into this as well and couldn’t find the referenced SO post, so I opened a PR with the note in the readme. It’s not clear to me why we need kotlin.reflect, so let me know how I can update it with more detail if necessary.