Conflicting jetified-kotlin-reflect dependency

Question

When I build my Android project, I get the following message:

w: Runtime JAR files in the classpath should have the same version. These files were found in the classpath:
    /home/janek/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk7/1.3.10/4d147bf43060dc43d61b096e24da1e67dfe0c032/kotlin-stdlib-jdk7-1.3.10.jar (version 1.3)
    /home/janek/.gradle/caches/transforms-1/files-1.1/kotlin-reflect-1.0.6.jar/beba9d201a205f30041b70982540014d/jetified-kotlin-reflect-1.0.6.jar (version 1.0)
    /home/janek/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.3.11/4cbc5922a54376018307a731162ccaf3ef851a39/kotlin-stdlib-1.3.11.jar (version 1.3)
    /home/janek/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.3.11/d8b8e746e279f1c4f5e08bc14a96b82e6bb1de02/kotlin-stdlib-common-1.3.11.jar (version 1.3)
w: Some runtime JAR files in the classpath have an incompatible version. Consider removing them from the classpath

But I have no idea why jetified-kotlin-reflect is even in there, since It isn't a dependency and does not even appear in androidDependencies.

Do you know where it comes from or how I can resolve this error?

Answer 1

I guess the kotlin plugin will automatically add the kotlin-relfection.jar if you use reflection features like class literal syntax.

On the Java platform, the runtime component required for using the reflection features is distributed as a separate JAR file (kotlin-reflect.jar). This is done to reduce the required size of the runtime library for applications that do not use reflection features. If you do use reflection, please make sure that the .jar file is added to the classpath of your project.

I fixed the warnings by explicitly adding

implementation "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"

to my build.gradle.