Add the flat classpath type aggregating flat classpath instances

There's added AggregateFlatClassPath - an equivalent of
MergedClassPath from the old implementation. It is supposed to group
classpath instances handling different files being directories, zips
or jars.

Unlike in the case of the old (recursive) implementation, there won't
be a deep, nested hierarchy of classpath instances - just one root
(aggregate) and a flat structure of its children.

AggregateFlatClassPath ensures the distinction of classpath entries
and merges corresponding entries for class and source files into one
entry. This is required as SymbolLoaders class makes use of this kind
of ClassRepresentation.

There are also added unit tests which check whether
AggregateFlatClassPath obtains correct entries from classpath
instances specified in a constructor and whether it preserves the
ordering in the case of repeated entries. There's added a test type
of flat classpath using VirtualFiles so it's easy to check the real
behaviour.

2 files changed, 131 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala b/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala
new file mode 100644
index 0000000000..3f06264e3c
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/classpath/AggregateFlatClassPath.scala
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2014 Contributor. All rights reserved.
+ */
+package scala.tools.nsc.classpath
+
+import java.net.URL
+import scala.annotation.tailrec
+import scala.collection.mutable.ArrayBuffer
+import scala.reflect.io.AbstractFile
+import scala.tools.nsc.util.ClassPath
+import scala.tools.nsc.util.ClassRepresentation
+
+/**
+ * A classpath unifying multiple class- and sourcepath entries.
+ * Flat classpath can obtain entries for classes and sources independently
+ * so it tries to do operations quite optimally - iterating only these collections
+ * which are needed in the given moment and only as far as it's necessary.
+ * @param aggregates classpath instances containing entries which this class processes
+ */
+case class AggregateFlatClassPath(aggregates: Seq[FlatClassPath]) extends FlatClassPath {
+
+  override def findClassFile(className: String): Option[AbstractFile] = {
+    @tailrec
+    def find(aggregates: Seq[FlatClassPath]): Option[AbstractFile] =
+      if (aggregates.nonEmpty) {
+        val classFile = aggregates.head.findClassFile(className)
+        if (classFile.isDefined) classFile
+        else find(aggregates.tail)
+      } else None
+
+    find(aggregates)
+  }
+
+  override def findClass(className: String): Option[ClassRepresentation[AbstractFile]] = {
+    val (pkg, simpleClassName) = PackageNameUtils.separatePkgAndClassNames(className)
+
+    @tailrec
+    def findEntry[T <: ClassRepClassPathEntry](aggregates: Seq[FlatClassPath], getEntries: FlatClassPath => Seq[T]): Option[T] =
+      if (aggregates.nonEmpty) {
+        val entry = getEntries(aggregates.head)
+          .find(_.name == simpleClassName)
+        if (entry.isDefined) entry
+        else findEntry(aggregates.tail, getEntries)
+      } else None
+
+    val classEntry = findEntry(aggregates, classesGetter(pkg))
+    val sourceEntry = findEntry(aggregates, sourcesGetter(pkg))
+
+    mergeClassesAndSources(classEntry.toList, sourceEntry.toList).headOption
+  }
+
+  override def asURLs: Seq[URL] = aggregates.flatMap(_.asURLs)
+
+  override def asClassPathStrings: Seq[String] = aggregates.map(_.asClassPathString).distinct
+
+  override def asSourcePathString: String = ClassPath.join(aggregates map (_.asSourcePathString): _*)
+
+  override private[nsc] def packages(inPackage: String): Seq[PackageEntry] = {
+    val aggregatedPackages = aggregates.flatMap(_.packages(inPackage)).distinct
+    aggregatedPackages
+  }
+
+  override private[nsc] def classes(inPackage: String): Seq[ClassFileEntry] =
+    getDistinctEntries(classesGetter(inPackage))
+
+  override private[nsc] def sources(inPackage: String): Seq[SourceFileEntry] =
+    getDistinctEntries(sourcesGetter(inPackage))
+
+  override private[nsc] def list(inPackage: String): FlatClassPathEntries = {
+    val (packages, classesAndSources) = aggregates.map(_.list(inPackage)).unzip
+    val distinctPackages = packages.flatten.distinct
+    val distinctClassesAndSources = mergeClassesAndSources(classesAndSources: _*)
+    FlatClassPathEntries(distinctPackages, distinctClassesAndSources)
+  }
+
+  /**
+   * Returns only one entry for each name. If there's both a source and a class entry, it
+   * creates an entry containing both of them. If there would be more than one class or source
+   * entries for the same class it always would use the first entry of each type found on a classpath.
+   */
+  private def mergeClassesAndSources(entries: Seq[ClassRepClassPathEntry]*): Seq[ClassRepClassPathEntry] = {
+    // based on the implementation from MergedClassPath
+    var count = 0
+    val indices = collection.mutable.HashMap[String, Int]()
+    val mergedEntries = new ArrayBuffer[ClassRepClassPathEntry](1024)
+
+    for {
+      partOfEntries <- entries
+      entry <- partOfEntries
+    } {
+      val name = entry.name
+      if (indices contains name) {
+        val index = indices(name)
+        val existing = mergedEntries(index)
+
+        if (existing.binary.isEmpty && entry.binary.isDefined)
+          mergedEntries(index) = ClassAndSourceFilesEntry(entry.binary.get, existing.source.get)
+        if (existing.source.isEmpty && entry.source.isDefined)
+          mergedEntries(index) = ClassAndSourceFilesEntry(existing.binary.get, entry.source.get)
+      }
+      else {
+        indices(name) = count
+        mergedEntries += entry
+        count += 1
+      }
+    }
+    mergedEntries.toIndexedSeq
+  }
+
+  private def getDistinctEntries[EntryType <: ClassRepClassPathEntry](getEntries: FlatClassPath => Seq[EntryType]): Seq[EntryType] = {
+    val seenNames = collection.mutable.HashSet[String]()
+    val entriesBuffer = new ArrayBuffer[EntryType](1024)
+    for {
+      cp <- aggregates
+      entry <- getEntries(cp) if !seenNames.contains(entry.name)
+    } {
+      entriesBuffer += entry
+      seenNames += entry.name
+    }
+    entriesBuffer.toIndexedSeq
+  }
+
+  private def classesGetter(pkg: String) = (cp: FlatClassPath) => cp.classes(pkg)
+  private def sourcesGetter(pkg: String) = (cp: FlatClassPath) => cp.sources(pkg)
+}
diff --git a/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala b/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala
index f1bb6010a4..bbd244b647 100644
--- a/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala
+++ b/src/compiler/scala/tools/nsc/classpath/FlatClassPath.scala
@@ -47,6 +47,12 @@ object FlatClassPath {
 
 case class FlatClassPathEntries(packages: Seq[PackageEntry], classesAndSources: Seq[ClassRepClassPathEntry])
 
+object FlatClassPathEntries {
+  import scala.language.implicitConversions
+  // to have working unzip method
+  implicit def entry2Tuple(entry: FlatClassPathEntries) = (entry.packages, entry.classesAndSources)
+}
+
 sealed trait ClassRepClassPathEntry extends ClassRepresentation[AbstractFile]
 
 trait ClassFileEntry extends ClassRepClassPathEntry {