removes the admin link from the nav bar when the user is not admin; w…

…orked around a problem caused by lib-noir's sessions middleware and lazy sequences produced by Enlive (see comment in noir-auth-app.views.common/navigation-menu for details)

resources/public/navs.html

@@ -18,7 +18,7 @@
       <div class="nav">
 
         <ul id="logged-in-nav">
-          <li><a href="/admin">admin</a></li><!--
+          <li class="admin-nav-item"><a href="/admin">admin</a></li><!--
           http://stackoverflow.com/q/12168194/974795
           --><li><a href="/settings">settings</a></li><!--
           --><li><a data-method="post" href="/logout">log out</a></li>

src/noir_auth_app/views/admin.clj

@@ -156,7 +156,8 @@
         page-users 
             (if next-page-first-created-at (butlast users-batch) users-batch)]
 
-    (common/admin-layout
+    (doall  ; see comment in common/navigation-menu
+      (common/admin-layout
         {:title (i18n/translate :admin-page-title)
          :nav (common/navigation-menu)
          :content
@@ -167,7 +168,7 @@
                             :truncated-users-fields truncated-users-fields
                             :page-users page-users
                             :next-page-first-created-at
-                                next-page-first-created-at})})))
+                                next-page-first-created-at})}))))
 
 
 (defroutes admin-routes

src/noir_auth_app/views/common.clj

@@ -46,10 +46,30 @@
 ; p. 551 of "Clojure Programming"
 ; https://github.com/swannodette/enlive-tutorial/blob/master/src/tutorial/template3.clj
 (h/defsnippet not-logged-in-nav "public/navs.html" [:#not-logged-in-nav] [])
-(h/defsnippet logged-in-nav "public/navs.html" [:#logged-in-nav] [])
+(h/defsnippet logged-in-nav "public/navs.html" [:#logged-in-nav]
+  []
+  [:.admin-nav-item] #(when (session/get :admin) %))
 
 (defn navigation-menu []
-  (if (current-user) (logged-in-nav) (not-logged-in-nav)))
+  ; Before using (doall) below there was this exception
+  ;   java.lang.ClassCastException: clojure.lang.Var$Unbound cannot be cast to clojure.lang.IDeref
+  ; The reason is that logged-in-nav, like all defsnippet functions, yields a
+  ; lazy sequence (the 'class' function can be used to check this) and by the
+  ; time it's realized by Ring (which allows a sequence in :body, see
+  ; https://github.com/ring-clojure/ring/wiki/Concepts) the lib-noir's
+  ; session dynamic var is not bound anymore. Chas Emerick explains this and
+  ; provides a general solution in the form of a middleware here
+  ;   https://groups.google.com/d/topic/enlive-clj/0WOG2CDqUDY/discussion
+  ; For the moment though, I've decided to just solve this specific case
+  ; using 'doall' to avoid the overhead that the general solution imposes on
+  ; every request.
+  ; On the other hand, like Christophe Grand says, this is something that
+  ; should probably be solved in the wrap-noir-session middleware:
+  ; "Given that per Ring's spec, :body may be lazy seqs, I would tend to say
+  ; that it's up to the authors of middlewares which introduce dynamic
+  ; binding to ensure that this case is covered."
+  ; https://groups.google.com/d/topic/enlive-clj/CKuJHxaHkGY/discussion
+  (if (current-user) (doall (logged-in-nav)) (not-logged-in-nav)))
 
 
 ;; Layouts

src/noir_auth_app/views/users.clj

@@ -34,7 +34,7 @@
 
 
 (defn save-user-info-in-session [{:keys [_id lowercase_username]}]
-  (when true ;(= lowercase_username "admin") 
+  (when true  ;(= lowercase_username "admin")
         (session/put! :admin true))
   (session/put! :user-id _id))