"org.fusesource.scalate.TemplateException: loader constraint violation" when using SBTs embedded Jetty and scalatra/scalate

Question

I started getting this error yesterday when using the embedded 'jetty-run' task in SBT. I reverted my code to a previous version and it's still happening.

Note that I packaged up the application and deployed it in an actual jetty instance and I don't get the error. I started getting this error after adding some dependencies to my project (may or may not be related), but have since removed them.

I tried 'clean' 'clean-lib' and 'clean-cache' as well as cleaning out my ~/.m2/repository, ~/.ivy2/cache and project/boot directories.

Anybody have any other ideas?

The line that is blowing up is:

templateEngine.layout(uri, Map("flash" -> flash))

More of the stack trace is below:

org.fusesource.scalate.TemplateException: loader constraint violation: when resolving method "scala.tools.nsc.Settings.(Lscala/Function1;)V" the class loader (instance of sbt/jetty/LazyJettyRun7$SbtWebAppLoader$1) of the current class, org/fusesource/scalate/support/ScalaCompiler, and the class loader (instance of java/net/URLClassLoader) for resolved class, scala/tools/nsc/Settings, have different Class objects for the type scala/Function1 used in the signature
    at org.fusesource.scalate.TemplateEngine.compileAndLoad(TemplateEngine.scala:775)
    at org.fusesource.scalate.TemplateEngine.compileAndLoadEntry(TemplateEngine.scala:637)
    at org.fusesource.scalate.TemplateEngine.liftedTree1$1(TemplateEngine.scala:368)
    at org.fusesource.scalate.TemplateEngine.load(TemplateEngine.scala:362)
    at org.fusesource.scalate.TemplateEngine.load(TemplateEngine.scala:420)
    at org.fusesource.scalate.TemplateEngine.layout(TemplateEngine.scala:521)
    at com.ford.testbuilder.web.AppDefaults$class.com$ford$testbuilder$web$AppDefaults$$render(SharedTraits.scala:79)
    at com.ford.testbuilder.web.AppDefaults$$anonfun$6.apply(SharedTraits.scala:52)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$mcV$sp$2$$anonfun$6.apply(ScalatraKernel.scala:133)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$mcV$sp$2$$anonfun$6.apply(ScalatraKernel.scala:133)
    at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
    at scala.collection.immutable.List.foreach(List.scala:45)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:44)
    at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:42)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$mcV$sp$2.apply$mcV$sp(ScalatraKernel.scala:133)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$mcV$sp$2.apply(ScalatraKernel.scala:121)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$mcV$sp$2.apply(ScalatraKernel.scala:121)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(ScalatraKernel.scala:121)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply(ScalatraKernel.scala:121)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply(ScalatraKernel.scala:121)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1.apply$mcV$sp(ScalatraKernel.scala:120)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1.apply(ScalatraKernel.scala:120)
    at org.scalatra.ScalatraKernel$$anonfun$handle$1.apply(ScalatraKernel.scala:120)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.ScalatraKernel$class.handle(ScalatraKernel.scala:119)
    at com.ford.testbuilder.web.LoginServlet.org$scalatra$CookieSupport$$super$handle(LoginServlet.scala:10)
    at org.scalatra.CookieSupport$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply$mcV$sp(CookieSupport.scala:102)
    at org.scalatra.CookieSupport$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply(CookieSupport.scala:102)
    at org.scalatra.CookieSupport$$anonfun$handle$1$$anonfun$apply$mcV$sp$1.apply(CookieSupport.scala:102)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.CookieSupport$$anonfun$handle$1.apply$mcV$sp(CookieSupport.scala:101)
    at org.scalatra.CookieSupport$$anonfun$handle$1.apply(CookieSupport.scala:101)
    at org.scalatra.CookieSupport$$anonfun$handle$1.apply(CookieSupport.scala:101)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.CookieSupport$class.handle(CookieSupport.scala:100)
    at com.ford.testbuilder.web.LoginServlet.org$scalatra$FlashMapSupport$$super$handle(LoginServlet.scala:10)
    at org.scalatra.FlashMapSupport$$anonfun$handle$1.apply$mcV$sp(flashMap.scala:101)
    at org.scalatra.FlashMapSupport$$anonfun$handle$1.apply(flashMap.scala:100)
    at org.scalatra.FlashMapSupport$$anonfun$handle$1.apply(flashMap.scala:100)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:71)
    at org.scalatra.FlashMapSupport$class.handle(flashMap.scala:100)

Answer 1

I figured this out after trying a fresh checkout on someone else's machine (which was working fine) and comparing the classpaths. I found that I had both the scala-library-2.8.1.jar as well as the scala-library.jar in my classpath.

This was caused by the following line in my project file:

override def filterScalaJars = false

Wasted the better part of a day on this :(