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, 243 insertions, 0 deletions

diff --git a/compiler/src/dotty/tools/dotc/classpath/DirectoryClassPath.scala b/compiler/src/dotty/tools/dotc/classpath/DirectoryClassPath.scala
new file mode 100644
index 000000000..94a6ad585
--- /dev/null
+++ b/compiler/src/dotty/tools/dotc/classpath/DirectoryClassPath.scala
@@ -0,0 +1,243 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package dotty.tools.dotc.classpath
+
+import java.io.File
+import java.net.{URI, URL}
+import java.nio.file.{FileSystems, Files, SimpleFileVisitor}
+import java.util.function.IntFunction
+import java.util
+import java.util.Comparator
+
+import scala.reflect.io.{AbstractFile, PlainFile}
+import dotty.tools.io.{ClassPath, ClassRepresentation, PlainNioFile}
+import FileUtils._
+import scala.collection.JavaConverters._
+
+/**
+ * A trait allowing to look for classpath entries in directories. It provides common logic for
+ * classes handling class and source files.
+ * It makes use of the fact that in the case of nested directories it's easy to find a file
+ * when we have a name of a package.
+ * It abstracts over the file representation to work with both JFile and AbstractFile.
+ */
+trait DirectoryLookup[FileEntryType <: ClassRepresentation] extends ClassPath {
+  type F
+
+  val dir: F
+
+  protected def emptyFiles: Array[F] // avoids reifying ClassTag[F]
+  protected def getSubDir(dirName: String): Option[F]
+  protected def listChildren(dir: F, filter: Option[F => Boolean] = None): Array[F]
+  protected def getName(f: F): String
+  protected def toAbstractFile(f: F): AbstractFile
+  protected def isPackage(f: F): Boolean
+
+  protected def createFileEntry(file: AbstractFile): FileEntryType
+  protected def isMatchingFile(f: F): Boolean
+
+  private def getDirectory(forPackage: String): Option[F] = {
+    if (forPackage == ClassPath.RootPackage) {
+      Some(dir)
+    } else {
+      val packageDirName = FileUtils.dirPath(forPackage)
+      getSubDir(packageDirName)
+    }
+  }
+
+  private[dotty] def packages(inPackage: String): Seq[PackageEntry] = {
+    val dirForPackage = getDirectory(inPackage)
+    val nestedDirs: Array[F] = dirForPackage match {
+      case None => emptyFiles
+      case Some(directory) => listChildren(directory, Some(isPackage))
+    }
+    val prefix = PackageNameUtils.packagePrefix(inPackage)
+    nestedDirs.map(f => PackageEntryImpl(prefix + getName(f)))
+  }
+
+  protected def files(inPackage: String): Seq[FileEntryType] = {
+    val dirForPackage = getDirectory(inPackage)
+    val files: Array[F] = dirForPackage match {
+      case None => emptyFiles
+      case Some(directory) => listChildren(directory, Some(isMatchingFile))
+    }
+    files.map(f => createFileEntry(toAbstractFile(f)))
+  }
+
+  private[dotty] def list(inPackage: String): ClassPathEntries = {
+    val dirForPackage = getDirectory(inPackage)
+    val files: Array[F] = dirForPackage match {
+      case None => emptyFiles
+      case Some(directory) => listChildren(directory)
+    }
+    val packagePrefix = PackageNameUtils.packagePrefix(inPackage)
+    val packageBuf = collection.mutable.ArrayBuffer.empty[PackageEntry]
+    val fileBuf = collection.mutable.ArrayBuffer.empty[FileEntryType]
+    for (file <- files) {
+      if (isPackage(file))
+        packageBuf += PackageEntryImpl(packagePrefix + getName(file))
+      else if (isMatchingFile(file))
+        fileBuf += createFileEntry(toAbstractFile(file))
+    }
+    ClassPathEntries(packageBuf, fileBuf)
+  }
+}
+
+trait JFileDirectoryLookup[FileEntryType <: ClassRepresentation] extends DirectoryLookup[FileEntryType] {
+  type F = File
+
+  protected def emptyFiles: Array[File] = Array.empty
+  protected def getSubDir(packageDirName: String): Option[File] = {
+    val packageDir = new File(dir, packageDirName)
+    if (packageDir.exists && packageDir.isDirectory) Some(packageDir)
+    else None
+  }
+  protected def listChildren(dir: File, filter: Option[File => Boolean]): Array[File] = {
+    val listing = filter match {
+      case Some(f) => dir.listFiles(mkFileFilter(f))
+      case None => dir.listFiles()
+    }
+
+    // Sort by file name for stable order of directory .class entries in package scope.
+    // This gives stable results ordering of base type sequences for unrelated classes
+    // with the same base type depth.
+    //
+    // Notably, this will stably infer`Product with Serializable`
+    // as the type of `case class C(); case class D(); List(C(), D()).head`, rather than the opposite order.
+    // On Mac, the HFS performs this sorting transparently, but on Linux the order is unspecified.
+    //
+    // Note this behaviour can be enabled in javac with `javac -XDsortfiles`, but that's only
+    // intended to improve determinism of the compiler for compiler hackers.
+    java.util.Arrays.sort(listing,
+      new java.util.Comparator[File] {
+        def compare(o1: File, o2: File) = o1.getName.compareTo(o2.getName)
+      })
+    listing
+  }
+  protected def getName(f: File): String = f.getName
+  protected def toAbstractFile(f: File): AbstractFile = new PlainFile(new scala.reflect.io.File(f))
+  protected def isPackage(f: File): Boolean = f.isPackage
+
+  assert(dir != null, "Directory file in DirectoryFileLookup cannot be null")
+
+  def asURLs: Seq[URL] = Seq(dir.toURI.toURL)
+  def asClassPathStrings: Seq[String] = Seq(dir.getPath)
+}
+
+object JrtClassPath {
+  import java.nio.file._, java.net.URI
+  def apply(): Option[ClassPath] = {
+    try {
+      val fs = FileSystems.getFileSystem(URI.create("jrt:/"))
+      Some(new JrtClassPath(fs))
+    } catch {
+      case _: ProviderNotFoundException | _: FileSystemNotFoundException =>
+        None
+    }
+  }
+}
+
+/**
+  * Implementation `ClassPath` based on the JDK 9 encapsulated runtime modules (JEP-220)
+  *
+  * https://bugs.openjdk.java.net/browse/JDK-8066492 is the most up to date reference
+  * for the structure of the jrt:// filesystem.
+  *
+  * The implementation assumes that no classes exist in the empty package.
+  */
+final class JrtClassPath(fs: java.nio.file.FileSystem) extends ClassPath with NoSourcePaths {
+  import java.nio.file.Path, java.nio.file._
+  type F = Path
+  private val dir: Path = fs.getPath("/packages")
+
+  // e.g. "java.lang" -> Seq("/modules/java.base")
+  private val packageToModuleBases: Map[String, Seq[Path]] = {
+    val ps = Files.newDirectoryStream(dir).iterator().asScala
+    def lookup(pack: Path): Seq[Path] = {
+      Files.list(pack).iterator().asScala.map(l => if (Files.isSymbolicLink(l)) Files.readSymbolicLink(l) else l).toList
+    }
+    ps.map(p => (p.toString.stripPrefix("/packages/"), lookup(p))).toMap
+  }
+
+  override private[dotty] def packages(inPackage: String): Seq[PackageEntry] = {
+    def matches(packageDottedName: String) =
+      if (packageDottedName.contains("."))
+        packageOf(packageDottedName) == inPackage
+      else inPackage == ""
+    packageToModuleBases.keysIterator.filter(matches).map(PackageEntryImpl(_)).toVector
+  }
+  private[dotty] def classes(inPackage: String): Seq[ClassFileEntry] = {
+    if (inPackage == "") Nil
+    else {
+      packageToModuleBases.getOrElse(inPackage, Nil).flatMap(x =>
+        Files.list(x.resolve(inPackage.replace('.', '/'))).iterator().asScala.filter(_.getFileName.toString.endsWith(".class"))).map(x =>
+        ClassFileEntryImpl(new PlainNioFile(x))).toVector
+    }
+  }
+
+  override private[dotty] def list(inPackage: String): ClassPathEntries =
+    if (inPackage == "") ClassPathEntries(packages(inPackage), Nil)
+    else ClassPathEntries(packages(inPackage), classes(inPackage))
+
+  def asURLs: Seq[URL] = Seq(dir.toUri.toURL)
+  // We don't yet have a scheme to represent the JDK modules in our `-classpath`.
+  // java models them as entries in the new "module path", we'll probably need to follow this.
+  def asClassPathStrings: Seq[String] = Nil
+
+  def findClassFile(className: String): Option[AbstractFile] = {
+    if (!className.contains(".")) None
+    else {
+      val inPackage = packageOf(className)
+      packageToModuleBases.getOrElse(inPackage, Nil).iterator.flatMap{x =>
+        val file = x.resolve(className.replace('.', '/') + ".class")
+        if (Files.exists(file)) new PlainNioFile(file) :: Nil else Nil
+      }.take(1).toList.headOption
+    }
+  }
+  private def packageOf(dottedClassName: String): String =
+    dottedClassName.substring(0, dottedClassName.lastIndexOf("."))
+}
+
+case class DirectoryClassPath(dir: File) extends JFileDirectoryLookup[ClassFileEntryImpl] with NoSourcePaths {
+  override def findClass(className: String): Option[ClassRepresentation] = findClassFile(className) map ClassFileEntryImpl
+
+  def findClassFile(className: String): Option[AbstractFile] = {
+    val relativePath = FileUtils.dirPath(className)
+    val classFile = new File(s"$dir/$relativePath.class")
+    if (classFile.exists) {
+      val wrappedClassFile = new scala.reflect.io.File(classFile)
+      val abstractClassFile = new PlainFile(wrappedClassFile)
+      Some(abstractClassFile)
+    } else None
+  }
+
+  protected def createFileEntry(file: AbstractFile): ClassFileEntryImpl = ClassFileEntryImpl(file)
+  protected def isMatchingFile(f: File): Boolean = f.isClass
+
+  private[dotty] def classes(inPackage: String): Seq[ClassFileEntry] = files(inPackage)
+}
+
+case class DirectorySourcePath(dir: File) extends JFileDirectoryLookup[SourceFileEntryImpl] with NoClassPaths {
+  def asSourcePathString: String = asClassPathString
+
+  protected def createFileEntry(file: AbstractFile): SourceFileEntryImpl = SourceFileEntryImpl(file)
+  protected def isMatchingFile(f: File): Boolean = endsScalaOrJava(f.getName)
+
+  override def findClass(className: String): Option[ClassRepresentation] = findSourceFile(className) map SourceFileEntryImpl
+
+  private def findSourceFile(className: String): Option[AbstractFile] = {
+    val relativePath = FileUtils.dirPath(className)
+    val sourceFile = Stream("scala", "java")
+      .map(ext => new File(s"$dir/$relativePath.$ext"))
+      .collectFirst { case file if file.exists() => file }
+
+    sourceFile.map { file =>
+      val wrappedSourceFile = new scala.reflect.io.File(file)
+      val abstractSourceFile = new PlainFile(wrappedSourceFile)
+      abstractSourceFile
+    }
+  }
+
+  private[dotty] def sources(inPackage: String): Seq[SourceFileEntry] = files(inPackage)
+}