Properly close a number of classloaders

I discovered there were a number of places where closing a ClassLoader
didn't work correctly because I was assuming it was a URLClassLoader
when it was actually a ClasspathFilter. I also incorrectly imported the
wrong kind of URLClassLoader in Run.scala. Finally, I close the
SbtMetaBuildClassLoader when xMain exits now.

main/src/main/scala/sbt/Defaults.scala

@@ -29,6 +29,7 @@ import sbt.Scope.{ GlobalScope, ThisScope, fillTaskAxis }
 import sbt.internal.CommandStrings.ExportStream
 import sbt.internal._
 import sbt.internal.inc.JavaInterfaceUtil._
+import sbt.internal.inc.classpath.ClasspathFilter
 import sbt.internal.inc.{ ZincLmUtil, ZincUtil }
 import sbt.internal.io.{ Source, WatchState }
 import sbt.internal.librarymanagement.{ CustomHttp => _, _ }
@@ -795,13 +796,17 @@ object Defaults extends BuildCommon {
     // ((streams in test, loadedTestFrameworks, testLoader, testGrouping in test, testExecution in test, fullClasspath in test, javaHome in test, testForkedParallel, javaOptions in test) flatMap allTestGroupsTask).value,
     testResultLogger in (Test, test) :== TestResultLogger.SilentWhenNoTests, // https://github.com/sbt/sbt/issues/1185
     test := {
-      val loader = testLoader.value match { case u: URLClassLoader => Some(u); case _ => None }
+      val close = testLoader.value match {
+        case u: URLClassLoader  => Some(() => u.close())
+        case c: ClasspathFilter => Some(() => c.close())
+        case _                  => None
+      }
       val trl = (testResultLogger in (Test, test)).value
       val taskName = Project.showContextKey(state.value).show(resolvedScoped.value)
       try {
         trl.run(streams.value.log, executeTests.value, taskName)
       } finally {
-        loader.foreach(_.close())
+        close.foreach(_.apply())
       }
     },
     testOnly := inputTests(testOnly).evaluated,

main/src/main/scala/sbt/Main.scala

@@ -50,6 +50,11 @@ final class xMain extends xsbti.AppMain {
       case e: InvocationTargetException =>
         // This propogates xsbti.FullReload to the launcher
         throw e.getCause
+    } finally {
+      loader match {
+        case a: AutoCloseable => a.close()
+        case _                =>
+      }
     }
   }
   /*

main/src/main/scala/sbt/internal/ClassLoaders.scala

@@ -226,6 +226,11 @@ private[sbt] object SbtMetaBuildClassLoader {
     }
     new URLClassLoader(rest, updatedLibraryLoader) {
       override def toString: String = s"SbtMetaBuildClassLoader"
+      override def close(): Unit = {
+        super.close()
+        updatedLibraryLoader.close()
+        interfaceLoader.close()
+      }
     }
   }
 }

run/src/main/scala/sbt/Run.scala

@@ -8,19 +8,19 @@
 package sbt
 
 import java.io.File
-import java.lang.reflect.{ Method, Modifier }
-import Modifier.{ isPublic, isStatic }
+import java.lang.reflect.Method
+import java.lang.reflect.Modifier.{ isPublic, isStatic }
+import java.net.URLClassLoader
 
-import sbt.internal.inc.classpath.ClasspathUtilities
 import sbt.internal.inc.ScalaInstance
+import sbt.internal.inc.classpath.{ ClasspathFilter, ClasspathUtilities }
 import sbt.internal.util.MessageOnlyException
 import sbt.io.Path
 import sbt.util.Logger
 
-import scala.reflect.internal.util.ScalaClassLoader.URLClassLoader
-import scala.util.{ Failure, Success, Try }
-import scala.util.control.NonFatal
 import scala.sys.process.Process
+import scala.util.control.NonFatal
+import scala.util.{ Failure, Success, Try }
 
 sealed trait ScalaRun {
   def run(mainClass: String, classpath: Seq[File], options: Seq[String], log: Logger): Try[Unit]
@@ -98,8 +98,9 @@ class Run(newLoader: Seq[File] => ClassLoader, trapExit: Boolean) extends ScalaR
       invokeMain(loader, main, options)
     } finally {
       loader match {
-        case u: URLClassLoader => u.close()
-        case _                 =>
+        case u: URLClassLoader  => u.close()
+        case c: ClasspathFilter => c.close()
+        case _                  =>
       }
     }
   }