Duplicate class Kotlin and Java libraries

[maikelvdh]

What version of protobuf and what language are you using?
Version: 4.30.0
Language: Java/Kotlin

What operating system (Linux, Windows, ...) and version?

Android

What did you expect to see

No duplicated classes between protobuf-java and protobuf-kotlin as the latter is depending on the former.

What did you see instead?

Duplicate class com.google.protobuf.DescriptorProtos$1 found in modules protobuf-java-4.30.0.jar -> protobuf-java-4.30.0 (com.google.protobuf:protobuf-java:4.30.0) and protobuf-kotlin-4.30.0.jar -> protobuf-kotlin-4.30.0 (com.google.protobuf:protobuf-kotlin:4.30.0)
     Duplicate class com.google.protobuf.JavaFeaturesProto$1 found in modules protobuf-java-4.30.0.jar -> protobuf-java-4.30.0 (com.google.protobuf:protobuf-java:4.30.0) and protobuf-kotlin-4.30.0.jar -> protobuf-kotlin-4.30.0 (com.google.protobuf:protobuf-kotlin:4.30.0)

[zhangskz]

Looking at the output of bazel build //java/kotlin:kotlin_mvn, looks like this did change between 29.x and 30.x. I think this is likely a side-effect from 27ddb9c#diff-6beaadbcf29efe51f8886f0626759ab3ebfaa5727df8e91a096e9d787a0596dd. Thinking this might have broken deploy_env which I think normally excludes //java/core from the jars for Kotlin:
https://github.com/bazel-contrib/rules_jvm_external/blob/1811c0dcee109aa9aeb377af9fff7d0d6bb39959/private/rules/kt_jvm_export.bzl#L10

[zhangskz]

Hm maybe not, doesn't seems to have the extra DescriptorProtos and JavaFeaturesProto class files at that commit (or bump to rules_jvm_external)

[mkruskal-google]

Interestingly, while 30.x is the first release to contain the JavaFeaturesProto and DescriptorProtos classes themselves, 29.x does contain nested classes from these which it shouldn't. So I think the root cause is likely much older, but for some reason it got worse in 30.x. For example, the following two class files are in our 29.x kotlin jar:

• com/google/protobuf/JavaFeaturesProto$JavaFeatures$Utf8Validation$Utf8ValidationVerifier.class
• com/google/protobuf/DescriptorProtos$FeatureSet$EnumType$EnumTypeVerifier.class

[mkruskal-google]

Yep, so those are both lite-only symbols. I think the problem here is that the deploy_env we pass to kt_jvm_export only lists the core target, so it only excludes those symbols. So any symbols from the lite jar won't get stripped. Before 30.x this was limited to enum verifiers, which apparently nobody noticed. We likely also had an ODR violation where both lite and core shipped DescriptorProtos and JavaFeaturesProto. In 30.x I'm guessing we fixed this, moving them exclusively to lite.

I confirmed that simply adding lite to deploy_env *in addition to` core fixes the issue in 30.x