[Build] Skip yamlRestTestCompatibility tests when no previous unreleased minor

[breskeby]

This was brought up by the community and by the performance team. We should keep
even older branches buildable as best as possible.

This fixes a configuration issue of yamlRestTestCompatibility tests when no unreleased
previous major is available.

[elasticsearchmachine]

Pinging @elastic/es-delivery (Team:Delivery)

[jozala]

These changes look good, but I have some general questions.

Do I understand correctly that without this fix, it now fail for 8.19 branch, because for 9.x branches we still have previous major last version unreleased, but not for 8.19?

Why do we always use previous major last unreleased version for that? I understand there might be a case (like for 8.19 now) that there is no such version. Should we use the last released version then instead of not running the tests at all?

[breskeby]

This originally came up as 9.0 was failing to be configured as there was no previous minor or did not calculate correctly. We assume here that there is always a previous unreleased version but often there isn't. e.g for 9.0. 8.19 is not compatible as 9.0 is only compatible with 8.18

…

On Tue, Dec 23, 2025 at 1:54 PM Mariusz Józala ***@***.***> wrote: ***@***.**** commented on this pull request. These changes look good, but I have some general questions. Do I understand correctly that without this fix, it now fail for 8.19 branch, because for 9.x branches we still have previous major last version unreleased, but not for 8.19? Why do we always use previous major last *unreleased* version for that? I understand there might be a case (like for 8.19 now) that there is no such version. Should we use the last released version then instead of not running the tests at all? — Reply to this email directly, view it on GitHub <#139648 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAS35BV4R6XXS576KZ7AV34DE3O7AVCNFSM6AAAAACPHVU2HGVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZTMMBXHEZDQNJWGQ> . You are receiving this because you were assigned.Message ID: ***@***.***>

[jozala]

This originally came up as 9.0 was failing to be configured as there was no previous minor or did not calculate correctly. We assume here that there is always a previous unreleased version but often there isn't. e.g for 9.0. 8.19 is not compatible as 9.0 is only compatible with 8.18

Is it expected that we skip these tests when there is no previous unreleased version or we should use previous released version in that case?
We still care about the REST compatibility in those cases, right?