Setting version type via script processor can trigger assertion

[stu-elastic]

Elasticsearch Version

8.3+ (including master)

Problem Description

If a script processor sets the version type to "external" without setting the version for the document, an assertion in IndexShard.applyIndexOperationOnPrimary, assert versionType.validateVersionForWrites(version), fires and terminates the node.

Rather than triggering the assertion, perhaps we could reject the document if validateVersionForWrites is false?

Steps to Reproduce

PUT _ingest/pipeline/vt
{               
  "description": "assert",
  "processors": [  
    {
      "script": {
        "description": "sets version type",
        "lang": "painless",
        "source": "ctx._version_type = 'external'"
      }
    }
  ]
}

POST write-pipeline/_doc/1?pipeline=vt
{ "foo": "bar" }

[ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [runTask-0] fatal error in thread [elasticsearch[runTask-0][write][T#9]], exiting
»  java.lang.AssertionError: null
»       at org.elasticsearch.index.shard.IndexShard.applyIndexOperationOnPrimary(IndexShard.java:879) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.bulk.TransportShardBulkAction.executeBulkItemRequest(TransportShardBulkAction.java:319) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.bulk.TransportShardBulkAction$2.doRun(TransportShardBulkAction.java:185) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.bulk.TransportShardBulkAction.performOnPrimary(TransportShardBulkAction.java:251) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.bulk.TransportShardBulkAction.dispatchedShardOperationOnPrimary(TransportShardBulkAction.java:131) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.bulk.TransportShardBulkAction.dispatchedShardOperationOnPrimary(TransportShardBulkAction.java:70) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.action.support.replication.TransportWriteAction$1.doRun(TransportWriteAction.java:210) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:773) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) ~[elasticsearch-8.3.0-SNAPSHOT.jar:8.3.0-SNAPSHOT]
»       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) ~[?:?]
»       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[?:?]
»       at java.lang.Thread.run(Thread.java:833) [?:?]

[elasticmachine]

Pinging @elastic/es-data-management (Team:Data Management)