Add trailing slash handler

modules/reitit-ring/src/reitit/ring.cljc

@@ -110,6 +110,35 @@
                    (respond nil)))]
          (f handlers))))))
 
+(defn redirect-trailing-slash-handler
+  "A ring handler that redirects a missing path if there is an
+  existing path that only differs in the ending slash.
+
+  | key     | description |
+  |---------|-------------|
+  | :method | :add - redirects slash-less to slashed |
+  |         | :strip - redirects slashed to slash-less |
+  |         | :both - works both ways (default) |
+  "
+  [{:keys [method] :or {method :both}}]
+  (let [redirect-handler (fn redirect-handler [request]
+                           (let [uri (:uri request)
+                                 maybe-redirect (fn maybe-redirect [path]
+                                                  (if (r/match-by-path (::r/router request) path)
+                                                    {:status 308 ; permanent redirect
+                                                     :headers {"Location" path}
+                                                     :body ""}))]
+                             (if (str/ends-with? uri "/")
+                               (if (not= method :add)
+                                 (maybe-redirect (subs uri 0 (-> uri count dec))))
+                               (if (not= method :strip)
+                                 (maybe-redirect (str uri "/"))))))]
+    (fn
+      ([request]
+       (redirect-handler request))
+      ([request respond _]
+       (respond (redirect-handler request))))))
+
 (defn create-default-handler
   "A default ring handler that can handle the following cases,
   configured via options: