Is protobuf-kotlin-lite a Kotlin equivalent of protobuf-javalite?

[marosseleng]

Hi guys,

basically, the question is in the title. I was following Google's codelab on Android DataStore backed by protocol buffers and they use -javalite artifact for protobuf.

Firstly, I set up the configuration as in the codelab (java bindings), but after a while, I noticed that Kotlin is also supported. So I updated the dependencies and replaced protobuf-javalite with protobuf-kotlin-lite:3.17.0. The modified build.gradle is as follows:

plugins {
    ...
    id 'com.google.protobuf' version '0.8.16'
}
...
dependencies {
    ...
    implementation 'com.google.protobuf:protobuf-kotlin-lite:3.17.0'
}
protobuf {
    protoc {
        artifact = "com.google.protobuf:protoc:3.17.0"
    }

    generateProtoTasks {
        all().each { task ->
            task.builtins {
                kotlin {
                    option 'lite'
                }
            }
        }
    }
}

However, on build, I am getting errors like these:

> A failure occurred while executing com.android.build.gradle.internal.tasks.CheckDuplicatesRunnable
   > Duplicate class com.google.protobuf.AbstractMessageLite found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AbstractMessageLite$Builder found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AbstractMessageLite$Builder$LimitedInputStream found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AbstractMessageLite$InternalOneOfEnum found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AbstractParser found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AbstractProtobufList found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)
 Duplicate class com.google.protobuf.AllocatedBuffer found in modules jetified-protobuf-javalite-3.17.0 (com.google.protobuf:protobuf-javalite:3.17.0) and jetified-protobuf-kotlin-lite-3.17.0 (com.google.protobuf:protobuf-kotlin-lite:3.17.0)

and so on.

Am I doing something wrong? Isn't kotlin-lite an equivalent of javalite?

[ejona86]

This repo is just for the gradle plugin; this seems a question better suited to the protobuf or protobuf-kotlin projects although in this case I think the problem isn't even with those projects.

"Duplicate class" means that there is ambiguity for which class should be used. jetified-protobuf-javalite seems to duplicate the classes of protobuf-javalite, so you can only have a dependency on one of those two libraries. I'm not familiar with the jetified version, but it is clearly causing trouble. It seems protobuf-kotlin-lite depends on the normal protobuf-javalite. I'd assume you have some other dependency (not shown in the code snippet) that is bringing in the jetified version which is causing your pain. I don't know who created the jetified version, but I'm very disappointed to see it.

[marosseleng]

@ejona86 From what I found out, the only javalite comes from protobuf-kotlin-lite. I do have jetifier enabled, maybe that could be a cause? Is there something to jetify within javalite? Those should be non-android libraries, right?

[ejona86]

I don't know why there are jetifier versions of these binaries. I've not really used jetifier.

[marosseleng]

I've got that set up as the part of android project. Now I am using only androidx libraries, so Jetifier shouldn't be necessary. Anyways, I disabled Jetifier, which made those duplication errors disappear, but now it seems that protobuf isn't generating the Kotlin file for the original message defined in .proto file:

syntax = "proto3";

option java_package = "com.marosseleng.example.datastore";
option java_multiple_files = true;

// reserve 1-15 for most frequently used. Those fields occupy 1 byte
// fields 16-2049 take 2 bytes.
message UserPreferences {
  bool onboarding_completed = 1;
}

I can see generated UserPreferencesKt.kt file that has lots of unresolved references to com.marosseleng.example.datastore.UserPreferences and there is also UserPrefsKt.kt (name corresponds to my protobuf file name) file which is empty. So I am still guessing whether something's wrong with the configuration.

I haven't find anything special regarding syntax in proto file or gradle compiler.

[marosseleng]

So I looked into protobuf repo here on Github and there is already this issue (protocolbuffers/protobuf#8631). This one thus might be closed, it really isn't issue of gradle plugin.

Thanks for help anyways!