Build: Exclude unpublished Kafka Connect runtime from the BOM

[vbhanuchander-lang]

Closes #18052.

The BOM adds every leaf project, but iceberg-kafka-connect-runtime builds ZIP distributions rather than Maven artifacts and disables its publishing tasks, so its POM is never published — the 1.11.0 POM returns 404. The BOM therefore advertises a coordinate that cannot resolve.

The grouping project iceberg-kafka-connect is already excluded by the existing childProjects.isEmpty() check, so the runtime module is the only affected one — it is the only publishing-disabled leaf project in the build.

Verifying this change

./gradlew :iceberg-bom:generatePomFileForApachePublication, then inspecting bom/build/publications/apache/pom-default.xml:

	artifacts in BOM	iceberg-kafka-connect-runtime
before	30	present
after	29	absent

Exactly one entry is removed. iceberg-kafka-connect, iceberg-kafka-connect-events and iceberg-kafka-connect-transforms are real published artifacts and remain.

I used an explicit exclusion list rather than deriving "does not publish" from the project state, because publishing is disabled inside that project's afterEvaluate while the BOM's constraints block is evaluated during configuration, so keying off task state here would depend on configuration ordering. Happy to switch to a shared property (for example a skipPublish flag set by the project and read here) if you would prefer something that cannot be forgotten when the next distribution-only module is added.

Generated-by: Claude Code (Opus 5)

[uros-b]

unpublishedProjects is a hardcoded one-entry list, a future distribution-only module that disables publishing in afterEvaluate must be added to this list manually or the BOM silently re-references an unpublished POM, reproducing the exact bug this PR fixes.

You already surfaced a self-maintaining alternative: a shared ext.skipPublish = true flag set in the project's own build file and readable in the configuration phase, which would handle future cases automatically. The explicit list is technically sound given the afterEvaluate-vs-configuration ordering constraint (reading task state in the configuration phase would be order-dependent), but Iceberg's connector surface is expanding, so perhaps we should consider the other approach?

[vbhanuchander-lang]

Agreed on the concern, so I tried the skipPublish approach properly before answering. It does not work here, and the reason is structural rather than a detail I can tidy up. Two experiments, both measured by regenerating the BOM POM:

1. ext.skipPublish = true in the runtime project, read with findProperty('skipPublish') in the BOM — 30 artifacts, runtime still present. The BOM's constraints block lives in the root build file, and Gradle evaluates the root before subproject build files, so at that moment kafka-connect/build.gradle has not run and the flag does not exist yet. This is the same ordering problem as reading task state, one step earlier.

2. Same flag, with the constraint population deferred inside gradle.projectsEvaluated { } so every project has been configured first — also 30. Constraints added at that point no longer reach the java-platform component.

So for a project-owned flag to work it would have to exist before root configuration, which in practice means declaring it in settings.gradle or root gradle.properties — still a central list, just moved further away from the project it describes.

Given that, the options I can see:

• keep the explicit list as-is;
• move the list into settings.gradle beside the include/name lines for these projects, so adding a distribution-only module puts the declaration and the exclusion in the same file;
• something lazier that I have not found — if you know a way to keep java-platform constraints open past project evaluation I am happy to try it.

My preference is the second, since it puts the exclusion where a new module is registered, but I do not feel strongly. Happy to push whichever you prefer.

For reference the current state is verified: 30 artifacts before, 29 after, with iceberg-kafka-connect, -events and -transforms retained.

[uros-b]

Thank you @vbhanuchander-lang! Option 2 sounds reasonable to me, but please ping the relevant / expert Iceberg committers here for final decision on how to proceed