Yada error handling

error_renderers.clj

(ns app.yada.error-renderers
  "Yada error renderer overrides"
  {:authors ["Michiel Borkent"]}
  (:require ...
            ...
            ...
            [reloaded.repl :as rr]
            [selmer.parser :as parser]
            [taoensso.timbre :refer [debug info error warn]]
            [yada.body :as body :refer [render-error get-error-message]]
            [yada.charset :as charset]
            [yada.handler :as handler] ;; load because of interning
            [yada.schema :as ys :refer [resource-coercer]]))

;; Note: @malcolmsparks recommended the following for adding application/json error handling
;; > For now, you can replace with your own error interceptor chain
;; > It is a bit arduous but worthwhile because you're then in complete control of error handling.
;; https://clojurians.slack.com/archives/C0702A7SB/p1493735777665719
;; But this also works. Maybe if we get into more issues, we'll try our own error interceptor chain.

;; See https://github.com/juxt/yada/blob/5d49342bcb994309b96673fb4a531ff313647c79/src/yada/handler.clj#L52
(intern 'yada.handler 'error-representations
        (ys/representation-seq
         (ys/representation-set-coercer
          [{:media-type #{"application/json"
                          "application/transit+json"
                          "application/json;pretty=true;q=0.96"
                          "text/plain;q=0.9"
                          "text/html;q=0.8"
                          "application/edn;q=0.6"
                          "application/edn;pretty=true;q=0.5"}
            :charset charset/platform-charsets}])))
...

(defn define-error-renderers [dev-env?]
  ;; See https://github.com/juxt/yada/blob/master/src/yada/body.clj#L214
  (defmethod render-error "text/html"
    [status ^Throwable error representation {:keys [id options] :as m}]
    (parser/render-file
     "error.html"
     {:status status
      :message (format "%d: %s" status (body/get-error-message status))
      :description (body/get-error-description status)
      :exception (when dev-env?
                   (let [baos (java.io.ByteArrayOutputStream.)
                         pw (java.io.PrintWriter.
                             (java.io.OutputStreamWriter. baos))]
                     (.printStackTrace error pw)
                     (.flush pw)
                     (String. (.toByteArray baos))))}))

  (defn api-error-renderer [status error representation
                            {:keys [id options method request]}]
    (if error ;; no error is provided with 404, etc.
      (let [error (unnest-exception error)]
        (or (and (= 400 status)
                 (let [maybe-error (:error (ex-data error))
                       maybe-error (when (map? maybe-error)
                                     (not-empty maybe-error))]
                   (and maybe-error
                        {:error maybe-error
                         :message "Schema validation error"})))
            (let [exception-data (ex-data error)
                  exception-type (:type exception-data)
                  error-response
                  (if-let [message (get error-messages exception-type)]
                    (error/error message error)
                    (case exception-type
                      ...
                      exception-data
                      ;; Fallback
                      (do
                        (when exception-type
                          (warn "Uncaught exception-type" exception-type))
                        (error/error error))))
                  error-response
                  (if-not dev-env?
                    (dissoc error-response :details)
                    error-response)
                  response (not-empty
                            (nn-hash-map :error (not-empty error-response)))]
              response)))
      (info "Responding with" status "on request"
            (select-keys request [:uri :params]))))

  ;; See https://github.com/juxt/yada/blob/master/src/yada/body.clj#L252
  (defmethod render-error "application/json"
    [status error representation ctx]
    (api-error-renderer status error representation ctx))

  ;; See https://github.com/juxt/yada/blob/master/src/yada/body.clj#L261
  (defmethod render-error "application/transit+json"
    [status error representation ctx]
    (api-error-renderer status error representation ctx)))


;;;; Scratch

(comment
  (rr/reset)
  )