Can someone please help me with this? <https://stackoverflow.com/questions/68511430/jackson-seriali...

# announcements

[Danish Ansari]

Can someone please help me with this?

https://stackoverflow.com/questions/68511430/jackson-serialisation-fails-by-throwing-kotlinreflectioninternalerror-when-seria

[Justin]

What are you using for your proguardFiles statement?

[Justin]

i.e. are you using one of the default android proguard files, e.g. proguard-android-optimize.txt

[Danish Ansari]

I have this inside build.gradle file

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), '<http://proguard-rules.pro|proguard-rules.pro>'

[Danish Ansari]

And I have written my rules in <http://proguard-rules.pro|proguard-rules.pro>

[Justin]

what version of kotlin and jackson are you using?

[Justin]

I was going to answer on stackoverflow but I can’t seem to reproduce your exact error, so first lets solve it here so we’re certain we’ve solved your exact error, then I’ll post the solution to stackoverflow for anyone else that has this issue

[Danish Ansari]

My Kotlin version is 1.4.31 and Jackson version is 2.12.0

Sorry for replying late, I dunno why I didn't get notification. Maybe because I was watching some YouTube tutorial on full screen.

[Justin]

no worries,
okay, so this error doesn’t indicate that there’s an issue with your model, it indicates that somehow, it can’t find the access for:

kotlin.collections.EmptyList.serialVersionUID: kotlin.Long

Did you try removing INFER_PROPERTY_MUTATORS ?

[Justin]

actually, nvm I guess that’s enabled by default

[Justin]

okay so the problem is literally that accessors and/or the field serialVersionUID in kotlin’s EmptyList object

[Danish Ansari]

were you able to replicate the issue?

[Justin]

unfortunately I wasn’t

[Justin]

to me, this looks like there’s an issue with serializing the object EmptyList because somehow kotlin reflection expects that the field serialVersionUID is there but r8 has removed it

[Justin]

r8 or proguard, either one

[Justin]

but you shouldn’t have to know that listOf() uses EmptyList object under the hood

[Justin]

try this very specific rule:

-keepclassmembers class kotlin.collections.EmptyList {
    static final long serialVersionUID;
}

[Danish Ansari]

Building...

[Justin]

I think what’s happening is that kotlin reflect is reading the kotlin.Metadata which provides information to the kotlin compiler (and kotlin reflect) about EmptyList which r8/proguard is minifying, but it is removing EmptyList.serialVersionUID so it never finds that field

[Justin]

that shouldn’t happen though, so what version of the android gradle plugin are you on?

[Danish Ansari]

Writing that specific rule worked like a charm 😅

My project's AGP version is 4.1.3

[Justin]

try removing the rule then using 4.2.2

[Justin]

r8 should properly update the kotlin.Metadata in the bytecode when it makes changes to the underlying class, but it looks like it’s not doing that

[Justin]

and since r8 is packaged with the android gradle plugin, first thing I’d try is a newer version of the android gradle plugin

[Danish Ansari]

Gradle syncing...

[Justin]

if this works that’d be ideal because then you don’t need to worry about the same issue with other classes and/or other bugs that may not have been resolved

[Justin]

it might make you update your gradle version to 6.7.1+

[Justin]

i.e. in gradle/wrapper/gradle-wrapper.properties , updating this value:
distributionUrl=https\:<//services.gradle.org/distributions/gradle-6.7.1-bin.zip>

[Danish Ansari]

yeah, done that. the build is taking a bit time with all the downloading n all

[Justin]

sounds good

[Danish Ansari]

woah, upgrading AGP version worked

[Justin]

okay so it was a bug in R8

[Justin]

I’ll post the answer to stackoverflow

[Danish Ansari]

I dunno in detail

[Danish Ansari]

Can you explain what exactly was the issue?

[Danish Ansari]

And is there any way to watch that particular issue as in Github or Google issue?

[Justin]

I will answer in stackoverflow, you just need to approve

[Danish Ansari]

yeah sure

[Justin]

I don’t know of an actual r8 issue, I’m just going based on what I know about kotlin reflection and r8

[Danish Ansari]

ok

[Danish Ansari]

Thanks a lot @Justin sir, you saved my day

[Justin]

no problem! happy to help

[Justin]

just answered in stackoverflow

[Danish Ansari]

Upvoted and approved

[Justin]

great!

[Danish Ansari]

Once again, thanks

[Danish Ansari]

and good night

[Justin]

no problem at all, night!