Call clojure code from scala sbt task

Question

I am trying to call some clojure code as an sbt task.

My build.sbt looks like

lazy val aTask = taskKey[Unit]("a task") libraryDependencies ++= Seq( "org.clojure" % "clojure" % "1.9.0" ) import clojure.java.api.Clojure import clojure.lang.IFn aTask := { val plus: IFn = Clojure.`var`("clojure.core", "+") println(plus.invoke(1, 4)) } 

Project Content /build.sbt

 resolvers += Resolver.mavenLocal libraryDependencies ++= Seq( "org.clojure" % "clojure" % "1.9.0" ) 

I also added clojure dep to project / build.sbt of my project.

When calling a task

The following error appears:

 [error] java.lang.ExceptionInInitializerError [error] at clojure.lang.Namespace.<init>(Namespace.java:34) [error] at clojure.lang.Namespace.findOrCreate(Namespace.java:176) [error] at clojure.lang.Var.intern(Var.java:148) [error] at clojure.java.api.Clojure.var(Clojure.java:82) [error] at clojure.java.api.Clojure.<clinit>(Clojure.java:96) [error] at $2d5a9b65ddee7e6a09cc$.$anonfun$$sbtdef$1(build.sbt:20) [error] at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12) [error] at sbt.std.Transform$$anon$3.$anonfun$apply$2(System.scala:46) [error] at sbt.std.Transform$$anon$4.work(System.scala:66) [error] at sbt.Execute.$anonfun$submit$2(Execute.scala:262) [error] at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16) [error] at sbt.Execute.work(Execute.scala:271) [error] at sbt.Execute.$anonfun$submit$1(Execute.scala:262) [error] at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:174) [error] at sbt.CompletionService$$anon$2.call(CompletionService.scala:36) [error] at java.util.concurrent.FutureTask.run(FutureTask.java:266) [error] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [error] at java.util.concurrent.FutureTask.run(FutureTask.java:266) [error] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [error] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [error] at java.lang.Thread.run(Thread.java:748) [error] Caused by: java.io.FileNotFoundException: Could not locate clojure/core__init.class or clojure/core.clj on classpath. [error] at clojure.lang.RT.load(RT.java:463) [error] at clojure.lang.RT.load(RT.java:426) [error] at clojure.lang.RT.doInit(RT.java:468) [error] at clojure.lang.RT.<clinit>(RT.java:336) 

Any pointers to what I could try would be helpful.

Answer 1

I think there is a problem with setting sbt loader classes. Clojure The RT class loads Clojure namespaces / classes using the class loader APIs . If sbt configures the class loader hierarchy and class loading strategy (e.g. parent first) so that RT classloader does not find Clojure classes through the class loader using, then it will fail with the error you get.

Unfortunately, I do not know sbt internals to determine how class loaders are configured. Maybe another question will help in the investigation: How to display the classpath used to start the task?