Improve classpath extraction from classloader:

- implement opt-in unpacking/caching of the jar collection archives,
  such as spring boot fat jars and WARs, to the temp dir, and creating
  a valid classpath from extracted archive
- turning it on for the new default jsr223 engine
- fallback to extracting classpath from resource URLs if the classloader
  is not known url-based one
- refactor and optimize extraction
- cache the last retrieved classpath in the default JSR-223 script engine
  factory

libraries/scripting/jvm-host-test/test/kotlin/script/experimental/jvmhost/test/ClassPathTest.kt

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.script.experimental.jvmhost.test
+
+import junit.framework.TestCase
+import org.junit.Assert
+import org.junit.Test
+import java.io.File
+import java.io.FileOutputStream
+import java.net.URLClassLoader
+import java.util.jar.JarEntry
+import java.util.jar.JarOutputStream
+import kotlin.script.experimental.jvm.util.classpathFromClassloader
+
+class ClassPathTest : TestCase() {
+
+    @Test
+    fun testExtractFromFat() {
+        val collection = createTempFile("col", ".jar").apply { createCollectionJar(emulatedCollectionFiles, "BOOT-INF") }
+        val cl = URLClassLoader(arrayOf(collection.toURI().toURL()), null)
+        val cp = classpathFromClassloader(cl, true)
+        Assert.assertTrue(cp != null && cp.isNotEmpty())
+
+        testUnpackedCollection(cp!!, emulatedCollectionFiles)
+    }
+}
+
+private val emulatedCollectionFiles = arrayOf(
+    "classes/a/b.class",
+    "lib/c-d.jar"
+)
+
+fun File.createCollectionJar(fileNames: Array<String>, infDirName: String) {
+    FileOutputStream(this).use { fileStream ->
+        val jarStream = JarOutputStream(fileStream)
+        jarStream.putNextEntry(JarEntry("$infDirName/classes/"))
+        jarStream.putNextEntry(JarEntry("$infDirName/lib/"))
+        for (name in fileNames) {
+            jarStream.putNextEntry(JarEntry("$infDirName/$name"))
+            jarStream.write(name.toByteArray())
+        }
+        jarStream.finish()
+    }
+}
+
+fun testUnpackedCollection(classpath: List<File>, fileNames: Array<String>) {
+
+    fun List<String>.checkFiles(root: File) = forEach {
+        val file = File(root, it)
+        Assert.assertTrue(file.exists())
+        Assert.assertEquals(it, file.readText())
+    }
+
+    val (classes, jars) = fileNames.partition { it.startsWith("classes") }
+    val (cpClasses, cpJars) = classpath.partition { it.isDirectory && it.name == "classes" }
+    Assert.assertTrue(cpClasses.size == 1)
+    classes.checkFiles(cpClasses.first().parentFile)
+    jars.checkFiles(cpJars.first().parentFile.parentFile)
+}