[CI] GetDataStreamActionTests testDataStreamInfoToXContent failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #9064 / release-tests
• elasticsearch-periodic #9057 / release-tests
• elasticsearch-periodic #9050 / release-tests
• elasticsearch-periodic #9043 / release-tests
• elasticsearch-periodic #9036 / release-tests
• elasticsearch-periodic #9029 / release-tests
• elasticsearch-periodic #9022 / release-tests
• elasticsearch-periodic #9015 / release-tests
• elasticsearch-periodic #9001 / release-tests
• elasticsearch-periodic #8994 / release-tests

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.action.datastreams.GetDataStreamActionTests.testDataStreamInfoToXContent" -Dtests.seed=B11A219C56277578 -Dbuild.snapshot=false -Dtests.jvm.argline="-Dbuild.snapshot=false" -Dlicense.key=x-pack/license-tools/src/test/resources/public.key -Dtests.locale=wae-Latn-CH -Dtests.timezone=Europe/Prague -Druntime.java=24

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.elasticsearch.xcontent.XContentGenerationException: com.fasterxml.jackson.core.JsonGenerationException: Can not write a null, expecting field name (context: Object)

Issue Reasons:

• [main] 10 consecutive failures in step release-tests
• [main] 10 failures in test testDataStreamInfoToXContent (2.3% fail rate in 443 executions)
• [main] 10 failures in step release-tests (100.0% fail rate in 10 executions)
• [main] 10 failures in pipeline elasticsearch-periodic (90.9% fail rate in 11 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

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

[nielsbauman]

Most likely caused by #130042. Could you have a look when you have time, @masseyke?

[masseyke]

Oh, it is because the feature flag is not enabled for unit tests for non-snapshot builds (it is enabled for yaml rest tests and integTests). I need to figure out how to do that.