Dummy implementation of Schema Map validator (to get more humane errors)

validator.clj

(require '[schema.core :as s])
(require '[schema.utils :as su])

(defn check-map [schema value]
  {:pre [(map? value)]}
  (if-let [value (s/check schema value)]
    (into {}
          (for [[k v] value]
            [k (cond
                 (symbol? v) (keyword v)
                 (instance? schema.utils.ValidationError v) 
                 (let [[not? [sym val]] (su/validation-error-explain v)]
                   (if (= not? 'not)
                     [(keyword sym) val]))
                 :else :unknown-error)]))))

(check-map {:a (s/maybe (s/constrained s/Int pos? 'should-be-positive)), :b String} 
           {:a -1})

; => {:a [:should-be-positive -1], :b :missing-required-key}