KIP-1072 — Add @FunctionalInterface annotation to Kafka Streams SAM methods

Discussion Streams

Proposes adding @FunctionalInterface annotations to all Kafka Streams single-abstract-method (SAM) interfaces so that Clojure 1.12's improved Java interop can pass Clojure functions directly to DSL operators. Without @FunctionalInterface, Clojure's SAM interop does not recognize these interfaces, requiring wrapper boilerplate in Clojure-based Streams applications like Jackdaw.

Details