SPARK-1933: Throw a more meaningful exception when a directory is passed to addJar/addFile.

https://issues.apache.org/jira/browse/SPARK-1933



Author: Reynold Xin <rxin@apache.org>

Closes #888 from rxin/addfile and squashes the following commits:

8c402a3 [Reynold Xin] Updated comment.
ff6c162 [Reynold Xin] SPARK-1933: Throw a more meaningful exception when a directory is passed to addJar/addFile.

(cherry picked from commit 90e281b5)
Signed-off-by: Reynold Xin <rxin@apache.org>

core/src/main/scala/org/apache/spark/HttpFileServer.scala

@@ -59,6 +59,13 @@ private[spark] class HttpFileServer(securityManager: SecurityManager) extends Lo
   }
 
   def addFileToDir(file: File, dir: File) : String = {
+    // Check whether the file is a directory. If it is, throw a more meaningful exception.
+    // If we don't catch this, Guava throws a very confusing error message:
+    //   java.io.FileNotFoundException: [file] (No such file or directory)
+    // even though the directory ([file]) exists.
+    if (file.isDirectory) {
+      throw new IllegalArgumentException(s"$file cannot be a directory.")
+    }
     Files.copy(file, new File(dir, file.getName))
     dir + "/" + file.getName
   }

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -794,7 +794,7 @@ class SparkContext(config: SparkConf) extends Logging {
     addedFiles(key) = System.currentTimeMillis
 
     // Fetch the file locally in case a job is executed using DAGScheduler.runLocally().
-    Utils.fetchFile(path, new File(SparkFiles.getRootDirectory), conf, env.securityManager)
+    Utils.fetchFile(path, new File(SparkFiles.getRootDirectory()), conf, env.securityManager)
 
     logInfo("Added file " + path + " at " + key + " with timestamp " + addedFiles(key))
     postEnvironmentUpdate()
@@ -932,13 +932,12 @@ class SparkContext(config: SparkConf) extends Logging {
               try {
                 env.httpFileServer.addJar(new File(fileName))
               } catch {
-                case e: Exception => {
+                case e: Exception =>
                   // For now just log an error but allow to go through so spark examples work.
                   // The spark examples don't really need the jar distributed since its also
                   // the app jar.
                   logError("Error adding jar (" + e + "), was the --addJars option used?")
                   null
-                }
               }
             } else {
               env.httpFileServer.addJar(new File(uri.getPath))