Integrate flat classpath with the compiler

This commit integrates with the compiler the whole flat classpath
representation build next to the recursive one as an alternative.

From now flat classpath really works and can be turned on. There's
added flag -YclasspathImpl with two options: recursive (the default
one) and flat.

It was needed to make the dynamic dispatch to the particular
classpath representation according to the chosen type of a classpath
representation.

There's added PathResolverFactory which is used instead of a concrete
implementation of a path resolver. It turned out that only a small
subset of path resolvers methods is used outside this class in Scala
sources. Therefore, PathResolverFactory returns an instance of a base
interface PathResolverResult providing only these used methods.

PathResolverFactory in combination with matches in some other places
ensures that in all places using classpath we create/get the proper
representation.

Also the classPath method in Global is modified to use the dynamic
dispatch. This is very important change as a return type changed to
the base ClassFileLookup providing subset of old ClassPath public
methods. It can be problematic if someone was using in his project
the explicit ClassPath type or public methods which are not provided
via ClassFileLookup. I tested flat classpath with sbt and Scala IDE
and there were no problems. Also was looking at sources of some other
projects like e.g. Scala plugin for IntelliJ and there shouldn't be
problems, I think, but it would be better to check these changes
using the community build.

Scalap's Main.scala is changed to be able to use both implementations
and also to use flags related to the classpath implementation.

The classpath invalidation is modified to work properly with the old
(recursive) classpath representation after changes made in a Global.
In the case of the attempt to use the invalidation for the flat cp it
just throws exception with a message that the flat one currently
doesn't support the invalidation. And also that's why the partest's
test for the invalidation has been changed to use (always) the old
implementation. There's added an adequate comment with TODO to this
file.

There's added partest test generating various dependencies
(directories, zips and jars with sources and class files) and testing
whether the compilation and further running an application works
correctly, when there are these various types of entries specified as
-classpath and -sourcepath. It should be a good approximation of real
use cases.

11 files changed, 133 insertions, 50 deletions

diff --git a/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala b/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
index ad75d02bff..1289d55c37 100644
--- a/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
+++ b/src/compiler/scala/tools/nsc/GenericRunnerSettings.scala
@@ -5,10 +5,11 @@
 
 package scala.tools.nsc
 
-import scala.tools.util.PathResolver
+import java.net.URL
+import scala.tools.util.PathResolverFactory
 
 class GenericRunnerSettings(error: String => Unit) extends Settings(error) {
-  def classpathURLs = new PathResolver(this).asURLs
+  def classpathURLs: Seq[URL] = PathResolverFactory.create(this).resultAsURLs
 
   val howtorun =
     ChoiceSetting(
diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index 2316fb7ce9..01e8829d6e 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -14,11 +14,10 @@ import scala.compat.Platform.currentTime
 import scala.collection.{ mutable, immutable }
 import io.{ SourceReader, AbstractFile, Path }
 import reporters.{ Reporter, ConsoleReporter }
-import util.{ ClassPath, MergedClassPath, StatisticsInfo, returning, stackTraceString }
+import util.{ ClassFileLookup, ClassPath, MergedClassPath, StatisticsInfo, returning }
 import scala.reflect.ClassTag
-import scala.reflect.internal.util.{ OffsetPosition, SourceFile, NoSourceFile, BatchSourceFile, ScriptSourceFile }
-import scala.reflect.internal.pickling.{ PickleBuffer, PickleFormat }
-import scala.reflect.io.VirtualFile
+import scala.reflect.internal.util.{ SourceFile, NoSourceFile, BatchSourceFile, ScriptSourceFile }
+import scala.reflect.internal.pickling.PickleBuffer
 import symtab.{ Flags, SymbolTable, SymbolTrackers }
 import symtab.classfile.Pickler
 import plugins.Plugins
@@ -35,6 +34,8 @@ import backend.opt.{ Inliners, InlineExceptionHandlers, ConstantOptimization, Cl
 import backend.icode.analysis._
 import scala.language.postfixOps
 import scala.tools.nsc.ast.{TreeGen => AstTreeGen}
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
 
 class Global(var currentSettings: Settings, var reporter: Reporter)
     extends SymbolTable
@@ -58,7 +59,12 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   class GlobalMirror extends Roots(NoSymbol) {
     val universe: self.type = self
-    def rootLoader: LazyType = new loaders.PackageLoader(classPath)
+    def rootLoader: LazyType = {
+      settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Flat => new loaders.PackageLoaderUsingFlatClassPath(FlatClassPath.RootPackage, flatClassPath)
+        case ClassPathRepresentationType.Recursive => new loaders.PackageLoader(recursiveClassPath)
+      }
+    }
     override def toString = "compiler mirror"
   }
   implicit val MirrorTag: ClassTag[Mirror] = ClassTag[Mirror](classOf[GlobalMirror])
@@ -104,7 +110,14 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
   type PlatformClassPath = ClassPath[AbstractFile]
   type OptClassPath = Option[PlatformClassPath]
 
-  def classPath: PlatformClassPath = platform.classPath
+  def classPath: ClassFileLookup[AbstractFile] = settings.YclasspathImpl.value match {
+    case ClassPathRepresentationType.Flat => flatClassPath
+    case ClassPathRepresentationType.Recursive => recursiveClassPath
+  }
+
+  private def recursiveClassPath: ClassPath[AbstractFile] = platform.classPath
+
+  private def flatClassPath: FlatClassPath = platform.flatClassPath
 
   // sub-components --------------------------------------------------
 
@@ -846,6 +859,9 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   /** Extend classpath of `platform` and rescan updated packages. */
   def extendCompilerClassPath(urls: URL*): Unit = {
+    if (settings.YclasspathImpl.value == ClassPathRepresentationType.Flat)
+      throw new UnsupportedOperationException("Flat classpath doesn't support extending the compiler classpath")
+
     val newClassPath = platform.classPath.mergeUrlsIntoClassPath(urls: _*)
     platform.currentClassPath = Some(newClassPath)
     // Reload all specified jars into this compiler instance
@@ -881,6 +897,9 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
    *                entries on the classpath.
    */
   def invalidateClassPathEntries(paths: String*): Unit = {
+    if (settings.YclasspathImpl.value == ClassPathRepresentationType.Flat)
+      throw new UnsupportedOperationException("Flat classpath doesn't support the classpath invalidation")
+
     implicit object ClassPathOrdering extends Ordering[PlatformClassPath] {
       def compare(a:PlatformClassPath, b:PlatformClassPath) = a.asClassPathString compare b.asClassPathString
     }
@@ -910,10 +929,10 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
           informProgress(s"classpath updated on entries [${subst.keys mkString ","}]")
           def mkClassPath(elems: Iterable[PlatformClassPath]): PlatformClassPath =
             if (elems.size == 1) elems.head
-            else new MergedClassPath(elems, classPath.context)
+            else new MergedClassPath(elems, recursiveClassPath.context)
           val oldEntries = mkClassPath(subst.keys)
           val newEntries = mkClassPath(subst.values)
-          mergeNewEntries(newEntries, RootClass, Some(classPath), Some(oldEntries), invalidated, failed)
+          mergeNewEntries(newEntries, RootClass, Some(recursiveClassPath), Some(oldEntries), invalidated, failed)
         }
     }
     def show(msg: String, syms: scala.collection.Traversable[Symbol]) =
diff --git a/src/compiler/scala/tools/nsc/ObjectRunner.scala b/src/compiler/scala/tools/nsc/ObjectRunner.scala
index 95264aeda6..7c14f4943f 100644
--- a/src/compiler/scala/tools/nsc/ObjectRunner.scala
+++ b/src/compiler/scala/tools/nsc/ObjectRunner.scala
@@ -18,14 +18,14 @@ trait CommonRunner {
    *  @throws NoSuchMethodException
    *  @throws InvocationTargetException
    */
-  def run(urls: List[URL], objectName: String, arguments: Seq[String]) {
+  def run(urls: Seq[URL], objectName: String, arguments: Seq[String]) {
     (ScalaClassLoader fromURLs urls).run(objectName, arguments)
   }
 
   /** Catches exceptions enumerated by run (in the case of InvocationTargetException,
    *  unwrapping it) and returns it any thrown in Left(x).
    */
-  def runAndCatch(urls: List[URL], objectName: String, arguments: Seq[String]): Either[Throwable, Boolean] = {
+  def runAndCatch(urls: Seq[URL], objectName: String, arguments: Seq[String]): Either[Throwable, Boolean] = {
     try   { run(urls, objectName, arguments) ; Right(true) }
     catch { case e: Throwable => Left(unwrap(e)) }
   }
diff --git a/src/compiler/scala/tools/nsc/ScriptRunner.scala b/src/compiler/scala/tools/nsc/ScriptRunner.scala
index 7d5c6f6fff..6d24b31531 100644
--- a/src/compiler/scala/tools/nsc/ScriptRunner.scala
+++ b/src/compiler/scala/tools/nsc/ScriptRunner.scala
@@ -8,7 +8,10 @@ package tools.nsc
 
 import io.{ AbstractFile, Directory, File, Path }
 import java.io.IOException
+import scala.tools.nsc.classpath.DirectoryFlatClassPath
 import scala.tools.nsc.reporters.{Reporter,ConsoleReporter}
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.ClassPath.DefaultJavaContext
 import util.Exceptional.unwrap
 
 /** An object that runs Scala code in script files.
@@ -112,8 +115,10 @@ class ScriptRunner extends HasCompileSocket {
     }
 
     def hasClassToRun(d: Directory): Boolean = {
-      import util.ClassPath.{ DefaultJavaContext => ctx }
-      val cp = ctx.newClassPath(AbstractFile.getDirectory(d))
+      val cp = settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Recursive => DefaultJavaContext.newClassPath(AbstractFile.getDirectory(d))
+        case ClassPathRepresentationType.Flat => DirectoryFlatClassPath(d.jfile)
+      }
       cp.findClass(mainClass).isDefined
     }
 
diff --git a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
index 4877bd9b80..6bd123c51f 100644
--- a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
+++ b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
@@ -7,7 +7,10 @@ package scala.tools.nsc
 package backend
 
 import io.AbstractFile
-import util.{ClassPath,MergedClassPath,DeltaClassPath}
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.{ ClassPath, DeltaClassPath, MergedClassPath }
+import scala.tools.util.FlatClassPathResolver
 import scala.tools.util.PathResolver
 
 trait JavaPlatform extends Platform {
@@ -19,10 +22,20 @@ trait JavaPlatform extends Platform {
   private[nsc] var currentClassPath: Option[MergedClassPath[AbstractFile]] = None
 
   def classPath: ClassPath[AbstractFile] = {
+    assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Recursive,
+      "To use recursive classpath representation you must enable it with -YclasspathImpl:recursive compiler option.")
+
     if (currentClassPath.isEmpty) currentClassPath = Some(new PathResolver(settings).result)
     currentClassPath.get
   }
 
+  private[nsc] lazy val flatClassPath: FlatClassPath = {
+    assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Flat,
+      "To use flat classpath representation you must enable it with -YclasspathImpl:flat compiler option.")
+
+    new FlatClassPathResolver(settings).result
+  }
+
   /** Update classpath with a substituted subentry */
   def updateClassPath(subst: Map[ClassPath[AbstractFile], ClassPath[AbstractFile]]) =
     currentClassPath = Some(new DeltaClassPath(currentClassPath.get, subst))
diff --git a/src/compiler/scala/tools/nsc/backend/Platform.scala b/src/compiler/scala/tools/nsc/backend/Platform.scala
index 439cc1efb8..c3bc213be1 100644
--- a/src/compiler/scala/tools/nsc/backend/Platform.scala
+++ b/src/compiler/scala/tools/nsc/backend/Platform.scala
@@ -8,6 +8,7 @@ package backend
 
 import util.ClassPath
 import io.AbstractFile
+import scala.tools.nsc.classpath.FlatClassPath
 
 /** The platform dependent pieces of Global.
  */
@@ -15,9 +16,12 @@ trait Platform {
   val symbolTable: symtab.SymbolTable
   import symbolTable._
 
-  /** The compiler classpath. */
+  /** The old, recursive implementation of compiler classpath. */
   def classPath: ClassPath[AbstractFile]
 
+  /** The new implementation of compiler classpath. */
+  private[nsc] def flatClassPath: FlatClassPath
+
   /** Update classpath with a substitution that maps entries to entries */
   def updateClassPath(subst: Map[ClassPath[AbstractFile], ClassPath[AbstractFile]])
 
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index d6650595eb..e259c543cf 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -202,6 +202,8 @@ trait ScalaSettings extends AbsScalaSettings
   val YmethodInfer    = BooleanSetting    ("-Yinfer-argument-types", "Infer types for arguments of overriden methods.")
   val etaExpandKeepsStar = BooleanSetting ("-Yeta-expand-keeps-star", "Eta-expand varargs methods to T* rather than Seq[T].  This is a temporary option to ease transition.").withDeprecationMessage(removalIn212)
   val inferByName     = BooleanSetting    ("-Yinfer-by-name", "Allow inference of by-name types. This is a temporary option to ease transition. See SI-7899.").withDeprecationMessage(removalIn212)
+  val YclasspathImpl  = ChoiceSetting     ("-YclasspathImpl", "implementation", "Choose classpath scanning method.", List(ClassPathRepresentationType.Recursive, ClassPathRepresentationType.Flat), ClassPathRepresentationType.Recursive)
+
   val YvirtClasses    = false // too embryonic to even expose as a -Y //BooleanSetting    ("-Yvirtual-classes", "Support virtual classes")
   val YdisableUnreachablePrevention = BooleanSetting("-Ydisable-unreachable-prevention", "Disable the prevention of unreachable blocks in code generation.")
   val YnoLoadImplClass = BooleanSetting   ("-Yno-load-impl-class", "Do not load $class.class files.")
@@ -329,3 +331,8 @@ trait ScalaSettings extends AbsScalaSettings
     val Discard = "discard"
   }
 }
+
+object ClassPathRepresentationType {
+  val Flat = "flat"
+  val Recursive = "recursive"
+}
diff --git a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
index 3b1ce2fd5c..6386da5725 100644
--- a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
+++ b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
@@ -6,14 +6,15 @@
 package scala.tools.nsc
 package symtab
 
+import classfile.ClassfileParser
 import java.io.IOException
 import scala.compat.Platform.currentTime
-import scala.tools.nsc.util.{ ClassPath, ClassRepresentation }
-import classfile.ClassfileParser
 import scala.reflect.internal.MissingRequirementError
 import scala.reflect.internal.util.Statistics
 import scala.reflect.io.{ AbstractFile, NoAbstractFile }
 import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.nsc.util.{ ClassPath, ClassRepresentation }
 
 /** This class ...
  *
@@ -327,8 +328,13 @@ abstract class SymbolLoaders {
        *
        */
       private type SymbolLoadersRefined = SymbolLoaders { val symbolTable: classfileParser.symbolTable.type }
+
       val loaders = SymbolLoaders.this.asInstanceOf[SymbolLoadersRefined]
-      override def classFileLookup: util.ClassFileLookup[AbstractFile] = platform.classPath
+
+      override def classFileLookup: util.ClassFileLookup[AbstractFile] = settings.YclasspathImpl.value match {
+        case ClassPathRepresentationType.Recursive => platform.classPath
+        case ClassPathRepresentationType.Flat => platform.flatClassPath
+      }
     }
 
     protected def description = "class file "+ classfile.toString
diff --git a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
index 2b7c6cca2c..c5f46dc140 100644
--- a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
+++ b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
@@ -8,6 +8,7 @@ package transform
 
 import symtab._
 import Flags._
+import scala.tools.nsc.util.ClassPath
 
 abstract class AddInterfaces extends InfoTransform { self: Erasure =>
   import global._                  // the global environment
@@ -67,25 +68,30 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
     val implName  = tpnme.implClassName(iface.name)
     val implFlags = (iface.flags & ~(INTERFACE | lateINTERFACE)) | IMPLCLASS
 
-    val impl0 = (
+    val impl0 = {
       if (!inClass) NoSymbol
-      else iface.owner.info.decl(implName) match {
-        case NoSymbol => NoSymbol
-        case implSym  =>
-          // Unlink a pre-existing symbol only if the implementation class is
-          // visible on the compilation classpath.  In general this is true under
-          // -optimise and not otherwise, but the classpath can use arbitrary
-          // logic so the classpath must be queried.
-          if (classPath.context.isValidName(implName + ".class")) {
-            iface.owner.info.decls unlink implSym
-            NoSymbol
-          }
-          else {
-            log(s"not unlinking $iface's existing implClass ${implSym.name} because it is not on the classpath.")
-            implSym
-          }
+      else {
+        val typeInfo = iface.owner.info
+        typeInfo.decl(implName) match {
+          case NoSymbol => NoSymbol
+          case implSym =>
+            // Unlink a pre-existing symbol only if the implementation class is
+            // visible on the compilation classpath. In general this is true under
+            // -optimise and not otherwise, but the classpath can use arbitrary
+            // logic so the classpath must be queried.
+            // TODO this is not taken into account by flat classpath yet
+            classPath match {
+              case cp: ClassPath[_] if !cp.context.isValidName(implName + ".class") =>
+                log(s"not unlinking $iface's existing implClass ${implSym.name} because it is not on the classpath.")
+                implSym
+              case _ =>
+                typeInfo.decls unlink implSym
+                NoSymbol
+            }
+        }
       }
-    )
+    }
+
     val impl = impl0 orElse {
       val impl = iface.owner.newImplClass(implName, iface.pos, implFlags)
       if (iface.thisSym != iface) {
diff --git a/src/compiler/scala/tools/reflect/ReflectMain.scala b/src/compiler/scala/tools/reflect/ReflectMain.scala
index 3ae21b6b98..a998a44643 100644
--- a/src/compiler/scala/tools/reflect/ReflectMain.scala
+++ b/src/compiler/scala/tools/reflect/ReflectMain.scala
@@ -5,13 +5,13 @@ import scala.tools.nsc.Driver
 import scala.tools.nsc.Global
 import scala.tools.nsc.Settings
 import scala.tools.nsc.util.ScalaClassLoader
-import scala.tools.util.PathResolver
+import scala.tools.util.PathResolverFactory
 
 object ReflectMain extends Driver {
 
   private def classloaderFromSettings(settings: Settings) = {
-    val classpath = new PathResolver(settings).result
-    ScalaClassLoader.fromURLs(classpath.asURLs, getClass.getClassLoader)
+    val classPathURLs = PathResolverFactory.create(settings).resultAsURLs
+    ScalaClassLoader.fromURLs(classPathURLs, getClass.getClassLoader)
   }
 
   override def newCompiler(): Global = new ReflectGlobal(settings, reporter, classloaderFromSettings(settings))
diff --git a/src/compiler/scala/tools/util/PathResolver.scala b/src/compiler/scala/tools/util/PathResolver.scala
index 797abc085c..315476953d 100644
--- a/src/compiler/scala/tools/util/PathResolver.scala
+++ b/src/compiler/scala/tools/util/PathResolver.scala
@@ -9,7 +9,7 @@ package util
 
 import java.net.URL
 import scala.tools.reflect.WrappedProperties.AccessControl
-import scala.tools.nsc.{ Settings }
+import scala.tools.nsc.Settings
 import scala.tools.nsc.util.{ ClassFileLookup, ClassPath, JavaClassPath }
 import scala.reflect.io.{ File, Directory, Path, AbstractFile }
 import scala.reflect.runtime.ReflectionUtils
@@ -17,6 +17,7 @@ import ClassPath.{ JavaContext, DefaultJavaContext, join, split }
 import PartialFunction.condOpt
 import scala.language.postfixOps
 import scala.tools.nsc.classpath.{ AggregateFlatClassPath, ClassPathFactory, FlatClassPath, FlatClassPathFactory }
+import scala.tools.nsc.settings.ClassPathRepresentationType
 
 // Loosely based on the draft specification at:
 // https://wiki.scala-lang.org/display/SIW/Classpath
@@ -172,7 +173,7 @@ object PathResolver {
       !ReflectionUtils.scalacShouldntLoadClassfile(name)
   }
 
-  // called from scalap
+  @deprecated("This method is no longer used be scalap and will be deleted", "2.11.5")
   def fromPathString(path: String, context: JavaContext = DefaultJavaContext): JavaClassPath = {
     val s = new Settings()
     s.classpath.value = path
@@ -183,24 +184,35 @@ object PathResolver {
    *  If there are arguments, show those in Calculated as if those options had been
    *  given to a scala runner.
    */
-  def main(args: Array[String]): Unit = {
+  def main(args: Array[String]): Unit =
     if (args.isEmpty) {
       println(Environment)
       println(Defaults)
-    }
-    else {
+    } else {
       val settings = new Settings()
       val rest = settings.processArguments(args.toList, processAll = false)._2
-      val pr = new PathResolver(settings)
-      println(" COMMAND: 'scala %s'".format(args.mkString(" ")))
+      val pr = PathResolverFactory.create(settings)
+      println("COMMAND: 'scala %s'".format(args.mkString(" ")))
       println("RESIDUAL: 'scala %s'\n".format(rest.mkString(" ")))
-      pr.result.show()
+
+      pr.result match {
+        case cp: JavaClassPath =>
+          cp.show()
+        case cp: AggregateFlatClassPath =>
+          println(s"ClassPath has ${cp.aggregates.size} entries and results in:\n${cp.asClassPathStrings}")
+      }
     }
-  }
+}
+
+trait PathResolverResult {
+  def result: ClassFileLookup[AbstractFile]
+
+  def resultAsURLs: Seq[URL] = result.asURLs
 }
 
 abstract class PathResolverBase[BaseClassPathType <: ClassFileLookup[AbstractFile], ResultClassPathType <: BaseClassPathType]
-(settings: Settings, classPathFactory: ClassPathFactory[BaseClassPathType]) {
+(settings: Settings, classPathFactory: ClassPathFactory[BaseClassPathType])
+  extends PathResolverResult {
 
   import PathResolver.{ AsLines, Defaults, ppcp }
 
@@ -304,7 +316,8 @@ abstract class PathResolverBase[BaseClassPathType <: ClassFileLookup[AbstractFil
     cp
   }
 
-  def asURLs: List[URL] = result.asURLs.toList
+  @deprecated("Use resultAsURLs instead of this one", "2.11.5")
+  def asURLs: List[URL] = resultAsURLs.toList
 
   protected def computeResult(): ResultClassPathType
 }
@@ -328,3 +341,12 @@ class FlatClassPathResolver(settings: Settings, flatClassPathFactory: ClassPathF
 
   override protected def computeResult(): AggregateFlatClassPath = AggregateFlatClassPath(containers.toIndexedSeq)
 }
+
+object PathResolverFactory {
+
+  def create(settings: Settings): PathResolverResult =
+    settings.YclasspathImpl.value match {
+      case ClassPathRepresentationType.Flat => new FlatClassPathResolver(settings)
+      case ClassPathRepresentationType.Recursive => new PathResolver(settings)
+    }
+}