Demo of validating and coercing EDN data with edamame and malli

schema.edn

{:id "Lillan"
 :tags #{:artesan :coffee ":hotel"}
 :address {:street "Ahlmanintie 29"
           :city "Tampere"
           :zip "33100"
           :lonlat [61.4858322, 23.7854658]}}

user.clj

(require '[malli.core :as m])
(require '[malli.transform :as mt])
(require '[edamame.core :as e])
(require '[clojure.walk :refer [prewalk]])

(defrecord Wrapped [])

(defn parse
  "Parses an EDN String with edamame and returns a tuple2 of edn-value & path-vec->loc"
  [s]
  (let [data (e/parse-string s {:postprocess map->Wrapped})
        unwrap-1 (fn [v] (if (instance? Wrapped v) (:obj v) v))
        unwrap (fn [v] (prewalk unwrap-1 v))
        collect (fn collect [acc path {:keys [loc obj]}]
                  (let [acc (assoc acc path loc)]
                    (cond
                      (map? obj) (reduce (fn [acc kv]
                                           (let [k (unwrap (key kv))
                                                 acc (collect acc (conj path [:key k]) (key kv))]
                                             (collect acc (conj path k) (val kv)))) acc obj)
                      (set? obj) (reduce (fn [acc v] (collect acc (conj path (unwrap v)) v)) acc obj)
                      (vector? obj) (reduce-kv (fn [acc i child] (collect acc (conj path i) child)) acc obj)
                      (sequential? obj) (transduce (map-indexed vector)
                                                   (completing (fn [acc [i child]]
                                                                 (collect acc (conj path i) child))) acc obj)

                      :else acc)))]
    [(unwrap data) (collect {} [] data)]))

(defn coercer
  "Takes a schema and optionally transformers and returns a coercer fn of string -> decoded|error,
   with error containing the edamame loc info under :loc for each actual error"
  [schema & transformers]
  (let [decode (m/decoder schema (apply mt/transformer {:name :edamame} transformers))
        explain (m/explainer schema)]
    (fn [s]
      (let [[data in->loc] (parse s)
            decoded (decode data)]
        (or (some-> (explain decoded)
                    (update :errors (partial map #(assoc % :loc (in->loc (:in %)))))
                    (assoc :type ::error)
                    (assoc :string s))
            decoded)))))

(defn error? [x] (= ::error (:type x)))

;;
;;
;;

(def Address
  [:map
   [:id string?]
   [:tags [:set keyword?]]
   [:address
    [:map
     [:street string?]
     [:city string?]
     [:zip int?]
     [:lonlat [:tuple double? double?]]]]])

(def data (slurp "schema.edn"))

((coercer Address) data)
;{:type :user/error
; :schema [:map
;          [:id string?]
;          [:tags [:set keyword?]]
;          [:address
;           :map
;           [:street string?]
;           [:city string?]
;           [:zip int?]
;           [:lonlat [:tuple double? double?]]]],
; :value {:tags #{":hotel" :coffee :artesan},
;         :address {:lonlat [61.4858322 23.7854658]
;                   :city "Tampere"
;                   :street "Ahlmanintie 29"
;                   :zip "33100"},
;         :id "Lillan"},
; :errors (#Error{:path [:tags 0],
;                 :in [:tags ":hotel"],
;                 :schema keyword?,
;                 :value ":hotel",
;                 :loc {:row 2, :col 27, :end-row 2, :end-col 35}}
;           #Error{:path [:address :zip],
;                  :in [:address :zip],
;                  :schema int?,
;                  :value "33100",
;                  :loc {:row 5, :col 17, :end-row 5, :end-col 24}}),
; :string "{:id \"Lillan\"
;           :tags #{:artesan :coffee \":hotel\"}
;           :address {:street \"Ahlmanintie 29\"
;                     :city \"Tampere\"
;                     :zip \"33100\"
;                     :lonlat [61.4858322, 23.7854658]}}
;          "}

((coercer Address (mt/string-transformer)) data)
{:id "Lillan"
 :tags #{:coffee :artesan ::hotel},
 :address {:street "Ahlmanintie 29"
           :zip 33100
           :city "Tampere"
           :lonlat [61.4858322 23.7854658]}}