rest.clj

(defmacro json-flash [method path params body]
  (let [flash# (gensym "flash")
        params# (assoc params flash# :flash)]
    `(~method ~path ~params#
              (let [r# (do ~@body)
                    r# (if-not (empty? ~flash#)
                         (assoc r# :flash ~flash#)
                         r#)]
                (-> r#
                    json/encode-to-str
                    response/response
                    (response/content-type "application/json"))))))