Fix #2186: Synchronize classpath handling with Scala 2.12

This commit is a very crude port of the classpath handling as it exists
in the 2.12.x branch of scalac (hash: 232d95a198c94da0c6c8393624e83e9b9ac84e81),
this replaces the existing Classpath code that was adapted from scalac
years ago.

This code was written by Grzegorz Kossakowski, Michał Pociecha, Lukas
Rytz, Jason Zaugg and other scalac contributors, many thanks to them!

For more information on this implementation, see the description of the
PR that originally added it to scalac: https://github.com/scala/scala/pull/4060

Changes made to the copied code to get it to compile with dotty:
- Rename scala.tools.nsc.util.ClassPath to dotty.tools.io.ClassPath
- Rename scala.tools.nsc.classpath.* to dotty.tools.dotc.classpath.*
- Replace "private[nsc]" by "private[dotty]"
- Changed `isClass` methods in FileUtils to skip Scala 2.11
  implementation classes (needed until we stop being retro-compatible with
  Scala 2.11)

I also copied PlainFile.scala from scalac to get access to
`PlainNioFile`.

1 files changed, 52 insertions, 0 deletions

diff --git a/compiler/src/dotty/tools/dotc/classpath/VirtualDirectoryClassPath.scala b/compiler/src/dotty/tools/dotc/classpath/VirtualDirectoryClassPath.scala
new file mode 100644
index 000000000..5b0855554
--- /dev/null
+++ b/compiler/src/dotty/tools/dotc/classpath/VirtualDirectoryClassPath.scala
@@ -0,0 +1,52 @@
+package dotty.tools.dotc.classpath
+
+import dotty.tools.io.ClassRepresentation
+import scala.reflect.io.{AbstractFile, Path, PlainFile, VirtualDirectory}
+import FileUtils._
+import java.net.URL
+
+import scala.reflect.internal.util.AbstractFileClassLoader
+import dotty.tools.io.ClassPath
+
+case class VirtualDirectoryClassPath(dir: VirtualDirectory) extends ClassPath with DirectoryLookup[ClassFileEntryImpl] with NoSourcePaths {
+  type F = AbstractFile
+
+  // From AbstractFileClassLoader
+  private final def lookupPath(base: AbstractFile)(pathParts: Seq[String], directory: Boolean): AbstractFile = {
+    var file: AbstractFile = base
+    for (dirPart <- pathParts.init) {
+      file = file.lookupName(dirPart, directory = true)
+      if (file == null)
+        return null
+    }
+
+    file.lookupName(pathParts.last, directory = directory)
+  }
+
+  protected def emptyFiles: Array[AbstractFile] = Array.empty
+  protected def getSubDir(packageDirName: String): Option[AbstractFile] =
+    Option(lookupPath(dir)(packageDirName.split('/'), directory = true))
+  protected def listChildren(dir: AbstractFile, filter: Option[AbstractFile => Boolean] = None): Array[F] = filter match {
+    case Some(f) => dir.iterator.filter(f).toArray
+    case _ => dir.toArray
+  }
+  def getName(f: AbstractFile): String = f.name
+  def toAbstractFile(f: AbstractFile): AbstractFile = f
+  def isPackage(f: AbstractFile): Boolean = f.isPackage
+
+  // mimic the behavior of the old nsc.util.DirectoryClassPath
+  def asURLs: Seq[URL] = Seq(new URL(dir.name))
+  def asClassPathStrings: Seq[String] = Seq(dir.path)
+
+  override def findClass(className: String): Option[ClassRepresentation] = findClassFile(className) map ClassFileEntryImpl
+
+  def findClassFile(className: String): Option[AbstractFile] = {
+    val relativePath = FileUtils.dirPath(className) + ".class"
+    Option(lookupPath(dir)(relativePath split '/', directory = false))
+  }
+
+  private[dotty] def classes(inPackage: String): Seq[ClassFileEntry] = files(inPackage)
+
+  protected def createFileEntry(file: AbstractFile): ClassFileEntryImpl = ClassFileEntryImpl(file)
+  protected def isMatchingFile(f: AbstractFile): Boolean = f.isClass
+}