json-read-with-error-context

(require '[clojure.edn :as edn]
         '[clojure.string :as str])

(defn parse-json
  "Parses JSON into EDN and rethrows failures with the error and nearby text."
  [s]
  (try
    (edn/read-string (str/replace s #"(?:\"(?:\\.|[^\"\\])*\")|null" #(if (= % "null") "nil" %)))
    (catch Exception e
      (let [trimmed (str/triml (str s))
            near    (subs trimmed 0 (min 40 (count trimmed)))]
        (throw (ex-info (str "Invalid JSON near " (pr-str near) ": " (ex-message e))
                        {:near near} e))))))