[SPARK-15782][YARN] Set spark.jars system property in client mode

## What changes were proposed in this pull request?

When `--packages` is specified with `spark-shell` the classes from those packages cannot be found, which I think is due to some of the changes in `SPARK-12343`. In particular `SPARK-12343` removes a line that sets the `spark.jars` system property in client mode, which is used by the repl main class to set the classpath.

## How was this patch tested?

Tested manually.

This system property is used by the repl to populate its classpath. If
this is not set properly the classes for external packages cannot be
found.

tgravescs vanzin as you may be familiar with this part of the code.

Author: Nezih Yigitbasi <nyigitbasi@netflix.com>

Closes #13527 from nezihyigitbasi/repl-fix.

3 files changed, 33 insertions, 1 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index d56946e932..d8701812eb 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -391,7 +391,7 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
 
     _conf.set("spark.executor.id", SparkContext.DRIVER_IDENTIFIER)
 
-    _jars = _conf.getOption("spark.jars").map(_.split(",")).map(_.filter(_.nonEmpty)).toSeq.flatten
+    _jars = Utils.getUserJars(_conf)
     _files = _conf.getOption("spark.files").map(_.split(",")).map(_.filter(_.nonEmpty))
       .toSeq.flatten
 
diff --git a/core/src/main/scala/org/apache/spark/util/Utils.scala b/core/src/main/scala/org/apache/spark/util/Utils.scala
index f9d05409e1..aebd98b3b0 100644
--- a/core/src/main/scala/org/apache/spark/util/Utils.scala
+++ b/core/src/main/scala/org/apache/spark/util/Utils.scala
@@ -2352,6 +2352,26 @@ private[spark] object Utils extends Logging {
     log.info(s"Started daemon with process name: ${Utils.getProcessName()}")
     SignalUtils.registerLogger(log)
   }
+
+  /**
+   * Unions two comma-separated lists of files and filters out empty strings.
+   */
+  def unionFileLists(leftList: Option[String], rightList: Option[String]): Set[String] = {
+    var allFiles = Set[String]()
+    leftList.foreach { value => allFiles ++= value.split(",") }
+    rightList.foreach { value => allFiles ++= value.split(",") }
+    allFiles.filter { _.nonEmpty }
+  }
+
+  def getUserJars(conf: SparkConf): Seq[String] = {
+    val sparkJars = conf.getOption("spark.jars")
+    if (conf.get("spark.master") == "yarn") {
+      val yarnJars = conf.getOption("spark.yarn.dist.jars")
+      unionFileLists(sparkJars, yarnJars).toSeq
+    } else {
+      sparkJars.map(_.split(",")).map(_.filter(_.nonEmpty)).toSeq.flatten
+    }
+  }
 }
 
 /**
diff --git a/core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala b/core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala
index 2718976992..0b020592b0 100644
--- a/core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala
+++ b/core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala
@@ -570,6 +570,18 @@ class SparkSubmitSuite
       appArgs.executorMemory should be ("2.3g")
     }
   }
+
+  test("comma separated list of files are unioned correctly") {
+    val left = Option("/tmp/a.jar,/tmp/b.jar")
+    val right = Option("/tmp/c.jar,/tmp/a.jar")
+    val emptyString = Option("")
+    Utils.unionFileLists(left, right) should be (Set("/tmp/a.jar", "/tmp/b.jar", "/tmp/c.jar"))
+    Utils.unionFileLists(emptyString, emptyString) should be (Set.empty)
+    Utils.unionFileLists(Option("/tmp/a.jar"), emptyString) should be (Set("/tmp/a.jar"))
+    Utils.unionFileLists(emptyString, Option("/tmp/a.jar")) should be (Set("/tmp/a.jar"))
+    Utils.unionFileLists(None, Option("/tmp/a.jar")) should be (Set("/tmp/a.jar"))
+    Utils.unionFileLists(Option("/tmp/a.jar"), None) should be (Set("/tmp/a.jar"))
+  }
   // scalastyle:on println
 
   // NOTE: This is an expensive operation in terms of time (10 seconds+). Use sparingly.