WIP reduce file stats in classpath setup

Author: retronym

src/compiler/scala/tools/nsc/classpath/ZipAndJarFileLookupFactory.scala

@@ -36,15 +36,16 @@ sealed trait ZipAndJarFileLookupFactory {
   private val cache = new FileBasedCache[ZipSettings, ClassPath with Closeable]
 
   def create(zipFile: AbstractFile, settings: Settings, closeableRegistry: CloseableRegistry): ClassPath = {
-    val disabled = (settings.YdisableFlatCpCaching.value && !settings.YforceFlatCpCaching.value) || zipFile.file == null
+    val jfile = zipFile.file
+    val disabled = (settings.YdisableFlatCpCaching.value && !settings.YforceFlatCpCaching.value) || jfile == null
     val zipSettings = ZipSettings(settings.releaseValue)
-    cache.checkCacheability(zipFile.toURL :: Nil, checkStamps = true, disableCache = disabled) match {
-      case Left(_) =>
-        val result: ClassPath with Closeable = createForZipFile(zipFile, zipSettings)
-        closeableRegistry.registerCloseable(result)
-        result
-      case Right(paths) =>
-        cache.getOrCreate(zipSettings, paths, () => createForZipFile(zipFile, zipSettings), closeableRegistry, checkStamps = true)
+
+    if (disabled) {
+      val result: ClassPath with Closeable = createForZipFile(zipFile, zipSettings)
+      closeableRegistry.registerCloseable(result)
+      result
+    } else {
+      cache.getOrCreate(zipSettings, Seq(jfile.toPath), () => createForZipFile(zipFile, zipSettings), closeableRegistry, checkStamps = true)
     }
   }
 

src/reflect/scala/reflect/io/AbstractFile.scala

@@ -18,7 +18,8 @@ import java.io.{BufferedOutputStream, ByteArrayOutputStream, IOException, InputS
 import java.io.{File => JFile}
 import java.net.URL
 import java.nio.ByteBuffer
-
+import java.nio.file.attribute.BasicFileAttributes
+import java.nio.file.{Files, NoSuchFileException}
 import scala.collection.AbstractIterable
 
 /**
@@ -46,10 +47,18 @@ object AbstractFile {
    * readable zip or jar archive, returns an abstract directory
    * backed by it. Otherwise, returns `null`.
    */
-  def getDirectory(file: File): AbstractFile =
-    if (file.isDirectory) new PlainFile(file)
-    else if (file.isFile && Path.isExtensionJarOrZip(file.jfile)) ZipArchive.fromFile(file)
+  def getDirectory(file: File): AbstractFile = {
+    val attrs = try {
+       Files.readAttributes(file.jfile.toPath, classOf[BasicFileAttributes])
+    } catch {
+      case _: IOException =>
+        return null
+    }
+
+    if (attrs.isDirectory) new PlainFile(file)
+    else if (attrs.isRegularFile && Path.isExtensionJarOrZip(file.jfile)) ZipArchive.fromFile(file)
     else null
+  }
 
   /**
    * If the specified URL exists and is a regular file or a directory, returns an