Rerender GET on POST on validation error

nodes.clj

(defn create-form [{:keys [env name type]}]
  (common/layout
   [:h2 (str "Create instance in " env)]
   (form-to [:post (str "/environments/" env "/create")]
       (hidden-field "env" env) (hidden-field "principal" "web-ui")
       (instance-fields name type)
       (submit-button "Create"))))

(defroutes node-routes

;; [...]

  (GET "/environments/:env/create" {params :params}
    (create-form params))

  (POST "/environments/:env/create" [env :as {instance :params}]
      (if (valid? instance)
        (do
          (fakeec2/create-instance instance)
          (redirect (str "/environments/" env)))
        (create-form instance))))