[SPARK-29292] Fix internal usages of mutable collection for Seq in 2.13

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 3.1.0
• Component/s: Spark Core
• Assignee: Sean R. Owen
• Reporter: Sean R. Owen
• Created: 29/Sep/19 19:58
• Updated: 22/Jul/20 20:10
• Resolved: 22/Jul/20 20:10

Description

Kind of related to https://issues.apache.org/jira/browse/SPARK-27681, but a simpler subset.

In 2.13, a mutable collection can't be returned as a scala.collection.Seq. It's easy enough to call .toSeq on these as that still works on 2.12.

[ERROR] [Error] /Users/seanowen/Documents/spark_2.13/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala:467: type mismatch;
 found   : Seq[String] (in scala.collection) 
 required: Seq[String] (in scala.collection.immutable) 

Issue Links

• is duplicated by: SPARK-27681 Use scala.collection.Seq explicitly instead of scala.Seq alias
• links to: [Github] Pull Request #28971 (srowen)
• links to: [Github] Pull Request #28971 (srowen)
• links to: [Github] Pull Request #29078 (srowen)
• links to: [Github] Pull Request #29111 (srowen)
• links to: [Github] Pull Request #29147 (srowen)