How to generate sbt fat jar with multi-release dependencies safely targeting java 8

Question

Given a scala project that depends on a library with java multi-release dependencies and targets java 8 only, sbt-assembly will log multiple warnings similar to

Fully-qualified classname does not match jar entry:
  jar entry: META-INF/versions/9/org/apache/logging/log4j/util/internal/DefaultObjectInputFilter.class
  class name: org/apache/logging/log4j/util/internal/DefaultObjectInputFilter.class
Omitting META-INF/versions/9/org/apache/logging/log4j/util/internal/DefaultObjectInputFilter.class.

What is the correct way to deal with these warnings and skip META_INF/versions/* that are not needed for jvm 8?

https://stackoverflow.com/questions/25144484/sbt-assembly-deduplication-found-error — Dmytro Mitin, Jan 14 '23 at 03:42

score 1 · Answer 1 · answered Jan 04 '23 at 22:36

As best I can tell this must be solved using assembly / assemblyShadeRules via something like:

assembly / assemblyShadeRules := Seq(
   /* Sadly patterns are not simple regex so we can't have
    * a single "OR" pattern or something similar and must 
    * enumerate all the possible version directories. Additionally,
    * `/` is not a valid pattern char so `.` must be used.
    */
    ShadeRule.zap("**module-info").inAll,
    ShadeRule.zap("*.versions.9.**").inAll,
    ShadeRule.zap("*.versions.11.**").inAll,
    ShadeRule.zap("*.versions.15.**").inAll
)

Merely setting assemblyMergeStrategy via something like

assembly / assemblyMergeStrategy := {
    case x if x.endsWith("module-info.class") => MergeStrategy.discard // Don't care about this for java8 so nuke it
    case PathList("META-INF", "versions", xs @ _*) => MergeStrategy.discard
}

is not enough to remove the warnings as they originate from the call to the pants based jarjar shader which is run before the the merging strategies are applied.

How to generate sbt fat jar with multi-release dependencies safely targeting java 8

1 Answers1