Handling Deferred responses for vanilla ring middleware

deferred-ring.clj

(require '[ring.middleware.session]
         '[manifold.deferred :as d])



(defn wrap-ring-async-handler
  "Converts given asynchronous Ring handler to Aleph-compliant handler."
  [handler]
  (fn [request]
    (let [response (d/deferred)]
      (handler request #(d/success! response %) #(d/error! response %))
      response)))



(defn wrap-deferred-handler
  "Chains the Deferred response of handler to respond and raise callbacks."
  [handler]
  (fn [request respond raise]
    (-> (d/chain (handler request)
                 respond)
        (d/catch raise))))



(defn ring-handler [request]
  (d/success-deferred {:body "hello"}))



(def handler
  (-> ring-handler
      wrap-deferred-handler
      ring.middleware.session/wrap-session
      ;; ... other middleware ...
      wrap-ring-async-handler))



(handler {:some :request})