SI-6502 Refactorings suggested by review

- Moves mergeUrlsIntoClassPath from Global into ClassPath
- Revises and documents AbstractFile.getURL

Author: heathermiller

src/compiler/scala/tools/nsc/Global.scala

@@ -846,36 +846,12 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   /** Extend classpath of `platform` and rescan updated packages. */
   def extendCompilerClassPath(urls: URL*): Unit = {
-    val newClassPath = mergeUrlsIntoClassPath(platform, urls: _*)
+    val newClassPath = platform.classPath.mergeUrlsIntoClassPath(urls: _*)
     platform.currentClassPath = Some(newClassPath)
     // Reload all specified jars into this compiler instance
     invalidateClassPathEntries(urls.map(_.getPath): _*)
   }
 
-  /** Merge classpath of `platform` and `urls` into merged classpath */
-  def mergeUrlsIntoClassPath(platform: JavaPlatform, urls: URL*): MergedClassPath[AbstractFile] = {
-    // Collect our new jars/directories and add them to the existing set of classpaths
-    val prevEntries = platform.classPath match {
-      case mcp: MergedClassPath[AbstractFile] => mcp.entries
-      case cp:  ClassPath[AbstractFile]       => List(cp)
-    }
-    val allEntries = (prevEntries ++
-      urls.map(url => platform.classPath.context.newClassPath(
-          if (url.getProtocol == "file") {
-            val f = new File(url.getPath)
-            if (f.isDirectory) io.AbstractFile.getDirectory(f)
-            else io.AbstractFile.getFile(f)
-          } else {
-            io.AbstractFile.getURL(url)
-          }
-        )
-      )
-    ).distinct
-
-    // Combine all of our classpaths (old and new) into one merged classpath
-    new MergedClassPath(allEntries, platform.classPath.context)
-  }
-
   // ------------ Invalidations ---------------------------------
 
   /** Is given package class a system package class that cannot be invalidated?

src/compiler/scala/tools/nsc/util/ClassPath.scala

@@ -197,6 +197,23 @@ abstract class ClassPath[T] {
   def packages: IndexedSeq[ClassPath[T]]
   def sourcepaths: IndexedSeq[AbstractFile]
 
+  /** The entries this classpath is composed of. In class `ClassPath` it's just the singleton list containing `this`.
+   *  Subclasses such as `MergedClassPath` typically return lists with more elements.
+   */
+  def entries: IndexedSeq[ClassPath[T]] = IndexedSeq(this)
+
+  /** Merge classpath of `platform` and `urls` into merged classpath */
+  def mergeUrlsIntoClassPath(urls: URL*): MergedClassPath[T] = {
+    // Collect our new jars/directories and add them to the existing set of classpaths
+    val allEntries =
+      (entries ++
+       urls.map(url => context.newClassPath(io.AbstractFile.getURL(url)))
+      ).distinct
+
+    // Combine all of our classpaths (old and new) into one merged classpath
+    new MergedClassPath(allEntries, context)
+  }
+
   /**
    * Represents classes which can be loaded with a ClassfileLoader and/or SourcefileLoader.
    */
@@ -322,7 +339,7 @@ extends MergedClassPath[T](original.entries map (e => subst getOrElse (e, e)), o
  * A classpath unifying multiple class- and sourcepath entries.
  */
 class MergedClassPath[T](
-  val entries: IndexedSeq[ClassPath[T]],
+  override val entries: IndexedSeq[ClassPath[T]],
   val context: ClassPathContext[T])
 extends ClassPath[T] {
   def this(entries: TraversableOnce[ClassPath[T]], context: ClassPathContext[T]) =

src/reflect/scala/reflect/io/AbstractFile.scala

@@ -48,14 +48,16 @@ object AbstractFile {
     else null
 
   /**
-   * If the specified URL exists and is a readable zip or jar archive,
-   * returns an abstract directory backed by it. Otherwise, returns
-   * `null`.
+   * If the specified URL exists and is a regular file or a directory, returns an
+   * abstract regular file or an abstract directory, respectively, backed by it.
+   * Otherwise, returns `null`.
    */
-  def getURL(url: URL): AbstractFile = {
-    if (url == null || !Path.isExtensionJarOrZip(url.getPath)) null
-    else ZipArchive fromURL url
-  }
+  def getURL(url: URL): AbstractFile =
+    if (url.getProtocol == "file") {
+      val f = new java.io.File(url.getPath)
+      if (f.isDirectory) getDirectory(f)
+      else getFile(f)
+    } else null
 
   def getResources(url: URL): AbstractFile = ZipArchive fromManifestURL url
 }