Lightweight GraphQL-like map querying

query.clj

(defn filter-map [m spec]
  (reduce-kv
   (fn [m* k v]
     (if (some? v)
       (if-let [m-val (get m k)]
         (let [res
               (if (map? v)
                 (if (sequential? m-val)
                   (mapv #(filter-map % v) m-val)
                   (filter-map m-val v))
                 m-val)]
           (assoc m* k res))
         m*)
       m*))
   {} spec))

(comment
  (filter-map {:a 1
               :d 2
               :b {:c 3 :e 5}
               :f [{:foo 1 :bar 2} {:foo 3 :bar 4}]}
              {:a true
               :b {:c true}
               :f {:foo true}
               :foo {:bar true}
               :bar false
               :baz nil})
  ;;=> {:a 1, :b {:c 3}, :f [{:foo 1} {:foo 3}]}
  )