Small improvements in DAV handler

plugins/libkolab/lib/kolab_storage_cache.php

@@ -541,7 +541,7 @@ class kolab_storage_cache
      *
      * @param string $uid Object UID
      *
-     * @return array The Kolab object represented as hash array
+     * @return array|null The Kolab object represented as hash array
      */
     public function get_by_uid($uid)
     {

plugins/libkolab/lib/kolab_storage_dav_folder.php

@@ -204,8 +204,7 @@ class kolab_storage_dav_folder extends kolab_storage_folder
      */
     public function get_uid()
     {
-        // TODO ???
+        return $this->id;
-        return '';
     }
 
     /**
@@ -380,6 +379,17 @@ class kolab_storage_dav_folder extends kolab_storage_folder
             $object['changed'] = new DateTime('now');
         }
 
+        // Make sure UID exists
+        if (empty($object['uid'])) {
+            if ($uid) {
+                $object['uid'] = $uid;
+            }
+            else {
+                $username = rcube::get_instance()->user->get_username();
+                $object['uid'] = strtoupper(md5(time() . uniqid(rand())) . '-' . substr(md5($username), 0, 16));
+            }
+        }
+
         // generate and save object message
         if ($content = $this->to_dav($object)) {
             $method   = $uid ? 'update' : 'create';

plugins/libkolab/lib/kolab_storage_folder.php

@@ -270,7 +270,7 @@ class kolab_storage_folder extends kolab_storage_folder_api
      *
      * @param string $uid Object UID
      *
-     * @return array The Kolab object represented as hash array
+     * @return array|false|null The Kolab object represented as hash array, False on error
      */
     public function get_object($uid)
     {