I think several option validation functions (e.g. check-preloads) display bad warnings when :optimizations is not provided at all (it defaults to :none

Either the validation functions should check the all-opts map which has the implicit default options added, or should use default optimizations value if it is nil

check-preloads: https://github.com/clojure/clojurescript/blob/296d0a69340e832b92ed742b3cd0304a06bea27f/src/main/clojure/cljs/closure.clj#L1878

and the call site with bare opts instead of all-opts: https://github.com/clojure/clojurescript/blob/296d0a69340e832b92ed742b3cd0304a06bea27f/src/main/clojure/cljs/closure.clj#L2239

@juhoteperi that makes sense, http://dev.clojure.org/jira/browse/CLJS-1996

@anmonteiro I think there is similar problem with other checkers too

we should probably just use all-opts everywhere hrm

Yeah