The Scala layer for Spacemacs uses Ensime by default. There is an error that made me struggle for weeks: Bad source jar kills the server: ZipException: error in opening zip file

The offending JAR was a transitive dependency of a project, and the solution offered on the issue was not clear for me.

This problem is tricky if you previously loaded the project into an IDE: they download by default all transitive dependencies with sources and javadoc, and the ivy cache is shared by all projects in the same machine.

Here is my solution, as found also on the issue, in case it helps others:

• determine which dependency is pulling the problem JAR with the sbt dependency graph plugin (note: the command whatDependsOn only works in interactive mode)
• move away the current ivy cache folder console $ mv ~/.ivy2/ ~/.ivy2_old
• (optional) create a new clone to have a known state console $ git clone $repo ~/dev/ensime-$repo
• edit build.sbt to add an exclusion rule for the transitive dependency at the line of the explicit dependency that needs it, e.g. sbt libraryDependencies ++= Seq( "com.company.notifications" % "notifications-schema" exclude("org.json", "json") )
• compile, go for a coffee while ivy downloads the internet :), then run ensime commands console $ sbt compile $ sbt ensimeConfig ensimeConfigProject