A modern programming language that makes developers happier.

kotlinlang

produces 
```
Caused by: org.gradle.api.publish.maven.InvalidMavenPublicationException: Invalid publication 'private': multiple artifacts with the identical extension and classifier ('jar', 'null').
	at org.gradle.api.publish.maven.internal.publisher.ValidatingMavenPublisher.checkNotDuplicate(ValidatingMavenPublisher.java:121)
	at org.gradle.api.publish.maven.internal.publisher.ValidatingMavenPublisher.checkNoDuplicateArtifacts(ValidatingMavenPublisher.java:107)
	at org.gradle.api.publish.maven.internal.publisher.ValidatingMavenPublisher.publish(ValidatingMavenPublisher.java:46)
	at org.gradle.api.publish.maven.tasks.PublishToMavenRepository$1.publish(PublishToMavenRepository.java:85)
	at org.gradle.api.publish.internal.PublishOperation.run(PublishOperation.java:36)
```
if you uncomment the commented line