[GitHub] manuzhang commented on a change in pull request #23896: [SPARK-26977][CORE] Fix warn against subclassing scala.App

[GitBox <gi...@apache.org>]

manuzhang commented on a change in pull request #23896: [SPARK-26977][CORE] Fix warn against subclassing scala.App
URL: https://github.com/apache/spark/pull/23896#discussion_r260332912
 
 

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 File path: core/src/main/scala/org/apache/spark/deploy/SparkSubmit.scala
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 @@ -828,9 +828,12 @@ private[spark] class SparkSubmit extends Logging {
     val app: SparkApplication = if (classOf[SparkApplication].isAssignableFrom(mainClass)) {
       mainClass.newInstance().asInstanceOf[SparkApplication]
     } else {
-      // SPARK-4170
-      if (classOf[scala.App].isAssignableFrom(mainClass)) {
-        logWarning("Subclasses of scala.App may not work correctly. Use a main() method instead.")
+      // SPARK-4170, SPARK-26977
+      Try {
+        if (classOf[scala.App].isAssignableFrom(Utils.classForName(s"$childMainClass$$"))) {
+          logWarning("Subclasses of scala.App may not work correctly. " +
+            "Use a main() method instead.")
+        }
 
 Review comment:
   1. Which indent is wrong ? `mvn checkstyle:checkstyle` runs fine for me. 
   2. Is there any case the original check would work ? 
   3. What should we do when `ClassNotFoundException` is caught ?Java app will always throw here. 
   4. I'll add more comments

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