Validating output from edamame with malli

deps.edn

{:deps {metosin/malli {:git/url "https://github.com/metosin/malli" :sha "230b1767729aad3e02568f1320855e2b45d2d9b5"}
        borkdude/edamame {:git/url "https://github.com/borkdude/edamame" :sha "64c7eb43950eb500ba7429dded48257cd15355ae"}
        }}

edamalli.clj

(ns edamalli.core
  (:require [edamame.core :as e]
            [malli.core :as m]
            [malli.transform :as mt]))

(defrecord WrappedNum [obj loc])

(defn postprocess [{:keys [:obj :loc]}]
  (if (number? obj) (->WrappedNum obj loc) obj))

(defn fail! [{:keys [:obj :loc]}]
  (throw (ex-info (str "so bad " obj "/" loc) {})))

(def <42 [:and int? [:< 42]])
(def Schema [:tuple keyword? [:map {:encode/success :obj,
                                    :encode/failure fail!} [:obj <42]]])
(def valid? (m/validator Schema))
(def success (m/encoder Schema (mt/transformer {:name :success})))
(def failure (m/encoder Schema (mt/transformer {:name :failure})))

(defn parse-validate-and-transform [s]
  (let [x (e/parse-string s {:postprocess postprocess})]
    (if (valid? x) (success x) (failure x))))

(defn -main [& _args]
  (parse-validate-and-transform "[:foo 42]")
  ;; TODO:
  ;; - validate that the WrappedNum contains value < 42
  ;; - then transform it to only that number
  ;; - else raise error, printing the location metadata of that number
  )