The additional-spring-configuration-metadata.json file is landing in generated JARs: refer to spring-boot-autoconfigure.jar as an example.
I assume this is unnecessary as the contents are already merged on spring-configuration-metadata.json produced by spring-boot-configuration-processor, and STS/plugins will not read it when the source is a JAR file.
I started a PR on this, but as per @wilkinsona comments, ideally it should support both maven, gradle and people who are not deriving from spring-boot-starter-parent.
See #28398
Comment From: snicoll
Thanks for the report and the PR @chicobento. We are already tracking an issue for this.
Duplicate of #27430
Comment From: wilkinsona
Apologies, @chicobento. I'd forgotten that we already had an issue for this.
Comment From: chicobento
Sorry guys, my bad, I should've done a better search before posting. Tks