This was a long and major effort, awesome to see it completed.
I believe the underlying issue holding Flink back from 2.12 support was also the ClosureCleaner taken from Spark[0].<p>[0] <a href="https://github.com/apache/flink/blob/dacc16b4fa6db6abfdbf73b99f26a5fd36b12acd/flink-scala/src/main/scala/org/apache/flink/api/scala/ClosureCleaner.scala#L33" rel="nofollow">https://github.com/apache/flink/blob/dacc16b4fa6db6abfdbf73b...</a>