Pedestal "prequeue" utility method for prepending interceptors to the interceptor chain

chain.clj

;; This is a snippet of code I used to prepend interceptors to the Pedestal interceptor chain.
;; It was written because of a situation in which I had to be sure that the added interceptors
;; executed immediately after the current interceptor. Would there be any interest in a PR to
;; add this to Pedestal, possible with a different API? E.g. instead of (prequeue) I could alter
;; the (chain/enqueue) function to accept a :location argument:
;;
;; (enqueue :location :front)
;; (enqueue :location :back)
;; (enqueue :location :after some-other-interceptor)

(ns foobar.core
  (:require
   [io.pedestal.interceptor :as interceptor]
   [io.pedestal.interceptor.chain :as chain]
   [io.pedestal.log :as log]))

(defn- pq->vec
  [persistent-queue]
  {:pre [(or (nil? persistent-queue)
             (instance? clojure.lang.PersistentQueue persistent-queue))]}
  (loop [pq persistent-queue
         acc []]
    (let [val (peek pq)]
      (if (nil? val)
        acc
        (recur (pop pq) (conj acc val))))))

(defn- pq-prepend
  [pq v]
  {:pre [(or (nil? pq)
             (instance? clojure.lang.PersistentQueue pq))
         (seq? v)]}
  (into clojure.lang.PersistentQueue/EMPTY
        (concat v (pq->vec pq))))

(defn prequeue
  "Adds interceptors to the front of context's execution queue. Creates
  the queue if necessary. Returns updated context."
  [context interceptors]
  {:pre (every? interceptor/interceptor? interceptors)}
  (log/trace :prequeue (map name interceptors) :context context)
  ;; NB: use ::chain/queue to match the namespace of the context key,
  ;; but this would change to ::queue if/when this went upstream.
  (let [chain-pq (get-in context [::chain/queue])
        combined (pq-prepend chain-pq interceptors)]
    (assoc-in context [::chain/queue] combined)))