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`.

3 files changed, 24 insertions, 13 deletions

diff --git a/compiler/src/dotty/tools/dotc/config/JavaPlatform.scala b/compiler/src/dotty/tools/dotc/config/JavaPlatform.scala
index 8bc18c387..d2a8e18a2 100644
--- a/compiler/src/dotty/tools/dotc/config/JavaPlatform.scala
+++ b/compiler/src/dotty/tools/dotc/config/JavaPlatform.scala
@@ -2,8 +2,8 @@ package dotty.tools
 package dotc
 package config
 
-import io.{AbstractFile,ClassPath,JavaClassPath,MergedClassPath,DeltaClassPath}
-import ClassPath.{ JavaContext, DefaultJavaContext }
+import io._
+import classpath.AggregateClassPath
 import core._
 import Symbols._, Types._, Contexts._, Denotations._, SymDenotations._, StdNames._, Names._
 import Flags._, Scopes._, Decorators._, NameOps._, util.Positions._
@@ -11,7 +11,7 @@ import transform.ExplicitOuter, transform.SymUtils._
 
 class JavaPlatform extends Platform {
 
-  private var currentClassPath: Option[MergedClassPath] = None
+  private var currentClassPath: Option[ClassPath] = None
 
   def classPath(implicit ctx: Context): ClassPath = {
     if (currentClassPath.isEmpty)
@@ -35,8 +35,12 @@ class JavaPlatform extends Platform {
     }
 
   /** Update classpath with a substituted subentry */
-  def updateClassPath(subst: Map[ClassPath, ClassPath]) =
-    currentClassPath = Some(new DeltaClassPath(currentClassPath.get, subst))
+  def updateClassPath(subst: Map[ClassPath, ClassPath]): Unit = currentClassPath.get match {
+    case AggregateClassPath(entries) =>
+      currentClassPath = Some(AggregateClassPath(entries map (e => subst.getOrElse(e, e))))
+    case cp: ClassPath =>
+      currentClassPath = Some(subst.getOrElse(cp, cp))
+  }
 
   def rootLoader(root: TermSymbol)(implicit ctx: Context): SymbolLoader = new ctx.base.loaders.PackageLoader(root, classPath)
 
diff --git a/compiler/src/dotty/tools/dotc/config/PathResolver.scala b/compiler/src/dotty/tools/dotc/config/PathResolver.scala
index 159989e6f..f0709f4d3 100644
--- a/compiler/src/dotty/tools/dotc/config/PathResolver.scala
+++ b/compiler/src/dotty/tools/dotc/config/PathResolver.scala
@@ -4,8 +4,9 @@ package config
 
 import java.net.{ URL, MalformedURLException }
 import WrappedProperties.AccessControl
-import io.{ ClassPath, JavaClassPath, File, Directory, Path, AbstractFile }
-import ClassPath.{ JavaContext, DefaultJavaContext, join, split }
+import io.{ ClassPath, File, Directory, Path, AbstractFile }
+import classpath.{AggregateClassPath, ClassPathFactory }
+import ClassPath.{ JavaContext, join, split }
 import PartialFunction.condOpt
 import scala.language.postfixOps
 import core.Contexts._
@@ -128,7 +129,7 @@ object PathResolver {
       )
   }
 
-  def fromPathString(path: String)(implicit ctx: Context): JavaClassPath = {
+  def fromPathString(path: String)(implicit ctx: Context): ClassPath = {
     val settings = ctx.settings.classpath.update(path)
     new PathResolver()(ctx.fresh.setSettings(settings)).result
   }
@@ -150,7 +151,11 @@ object PathResolver {
       val pr = new PathResolver()(ctx.fresh.setSettings(sstate))
       println(" COMMAND: 'scala %s'".format(args.mkString(" ")))
       println("RESIDUAL: 'scala %s'\n".format(rest.mkString(" ")))
-      pr.result.show
+
+      pr.result match {
+        case cp: AggregateClassPath =>
+          println(s"ClassPath has ${cp.aggregates.size} entries and results in:\n${cp.asClassPathStrings}")
+      }
     }
   }
 }
@@ -159,7 +164,7 @@ import PathResolver.{ Defaults, Environment, firstNonEmpty, ppcp }
 class PathResolver(implicit ctx: Context) {
   import ctx.base.settings
 
-  val context = ClassPath.DefaultJavaContext
+  private val classPathFactory = new ClassPathFactory
 
   private def cmdLineOrElse(name: String, alt: String) = {
     (commandLineFor(name) match {
@@ -214,7 +219,7 @@ class PathResolver(implicit ctx: Context) {
       else sys.env.getOrElse("CLASSPATH", ".")
     }
 
-    import context._
+    import classPathFactory._
 
     // Assemble the elements!
     // priority class path takes precedence
@@ -254,8 +259,8 @@ class PathResolver(implicit ctx: Context) {
 
   def containers = Calculated.containers
 
-  lazy val result: JavaClassPath = {
-    val cp = new JavaClassPath(containers.toIndexedSeq, context)
+  lazy val result: ClassPath = {
+    val cp = AggregateClassPath(containers.toIndexedSeq)
 
     if (settings.Ylogcp.value) {
       Console.println("Classpath built from " + settings.toConciseString(ctx.sstate))
diff --git a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
index 63c3d5f74..941434dd5 100644
--- a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
+++ b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
@@ -73,6 +73,8 @@ class ScalaSettings extends Settings.SettingGroup {
   val log = PhasesSetting("-Ylog", "Log operations during")
   val emitTasty = BooleanSetting("-YemitTasty", "Generate tasty in separate *.tasty file.")
   val Ylogcp = BooleanSetting("-Ylog-classpath", "Output information about what classpath is being applied.")
+  val YdisableFlatCpCaching  = BooleanSetting("-YdisableFlatCpCaching", "Do not cache flat classpath representation of classpath elements from jars across compiler instances.")
+
   val YnoImports = BooleanSetting("-Yno-imports", "Compile without importing scala.*, java.lang.*, or Predef.")
   val YnoPredef = BooleanSetting("-Yno-predef", "Compile without importing Predef.")
   val Yskip = PhasesSetting("-Yskip", "Skip")