[SPARK-3340] Deprecate ADD_JARS and ADD_FILES

I created a patch that disables the environment variables.
Thereby scala or python shell log a warning message to notify user about the deprecation
with the following message:
scala: "ADD_JARS environment variable is deprecated, use --jar spark submit argument instead"
python: "Warning: ADD_FILES environment variable is deprecated, use --py-files argument instead"

Is it what is expected or the code associated with the variables should be just completely removed?
Should it be somewhere documented?

Author: azagrebin <azagrebin@gmail.com>

Closes #4616 from azagrebin/master and squashes the following commits:

bab1aa9 [azagrebin] [SPARK-3340] Deprecate ADD_JARS and ADD_FILES: minor readability issue
0643895 [azagrebin] [SPARK-3340] Deprecate ADD_JARS and ADD_FILES: add warning messages
42f0107 [azagrebin] [SPARK-3340] Deprecate ADD_JARS and ADD_FILES

1 files changed, 4 insertions, 3 deletions

diff --git a/repl/scala-2.10/src/main/scala/org/apache/spark/repl/SparkILoop.scala b/repl/scala-2.10/src/main/scala/org/apache/spark/repl/SparkILoop.scala
index b4db3df795..8dc0e0c965 100644
--- a/repl/scala-2.10/src/main/scala/org/apache/spark/repl/SparkILoop.scala
+++ b/repl/scala-2.10/src/main/scala/org/apache/spark/repl/SparkILoop.scala
@@ -1064,15 +1064,16 @@ class SparkILoop(
   private def main(settings: Settings): Unit = process(settings)
 }
 
-object SparkILoop {
+object SparkILoop extends Logging {
   implicit def loopToInterpreter(repl: SparkILoop): SparkIMain = repl.intp
   private def echo(msg: String) = Console println msg
 
   def getAddedJars: Array[String] = {
     val envJars = sys.env.get("ADD_JARS")
-    val propJars = sys.props.get("spark.jars").flatMap { p =>
-      if (p == "") None else Some(p)
+    if (envJars.isDefined) {
+      logWarning("ADD_JARS environment variable is deprecated, use --jar spark submit argument instead")
     }
+    val propJars = sys.props.get("spark.jars").flatMap { p => if (p == "") None else Some(p) }
     val jars = propJars.orElse(envJars).getOrElse("")
     Utils.resolveURIs(jars).split(",").filter(_.nonEmpty)
   }