Regression: simulateIndexTemplate requires indexTemplate in 8.19.+ (worked in 8.19.0)

[MamathaJagadeesh]

Java API client version

8.19.+

Java version

17

Elasticsearch Version

8.19.+

Problem description

SimulateIndexTemplateRequest in the Java client appears to require the indexTemplate property in 8.19.+ versions.
When using the Java client in 8.19.+, the following throws a MissingRequiredPropertyException unless indexTemplate is set.
SimulateIndexTemplateResponse response = client.indices().simulateIndexTemplate(b -> b.name(indexName));
This worked correctly in 8.19.0, so it appears to be a regression in the 8.19.+ client.
In 8.19.+, the above fails with co.elastic.clients.util.MissingRequiredPropertyException: Missing required property 'SimulateIndexTemplateRequest.indexTemplate'
8.19.0 → works
8.19.+ → fails with MissingRequiredPropertyException
Server version: Elasticsearch 8.19.x

Expected behavior:
The request should succeed and simulate template resolution for the provided index name in 8.19.+, similar to how it used to succeed in 8.19.0

Is there a planned fix in a future client release?

[l-trotta]

Hello, thanks for reporting this! This is a breaking change introduced in 8.19.4 from this specification PR that I missed and failed to document, my bad.

What happened is, the SimulateIndexTemplateRequest was incomplete and missing the body definition, which was added in that PR, but it appears there's a bug in the java client generator, because the body is supposed to be optional, while the java client is requiring it.

I'll investigate, the bugfix should solve this issue by making indexTemplate optional as intended. Thanks!

[l-trotta]

@MamathaJagadeesh 8.19.13 will be out in a couple weeks with the fix!

[MamathaJagadeesh]

Thank you for providing the update and implementing the fix!