fix: do no hit LDAP if no exposed attribute is configured

lib/AppInfo/Application.php

@@ -111,6 +111,13 @@ public function registerEventListener() {
 
  try {
  $attrs = $uProxy->getExposedAttributes($targetUser->getUID());
+ if ($attrs === null || $attrs === false) {
+ // either there are no exposed attributes or the user isn't found in LDAP
+ // if there are no exposed attributes configured, we won't contact the LDAP server,
+ // so we don't know if the user really exists.
+ $event->setAttributes('user_ldap_state', 'Unknown');
+ return;
+ }
 
  $event->setAttributes('user_ldap_state', 'OK');
  foreach ($attrs as $key => $value) {

lib/User_LDAP.php

@@ -413,16 +413,21 @@ public function getAvatar($uid) {
  * only the first value will be returned.
  *
  * @param string $uid
- * @return array<string,string>|false key -> value map containing the attributes
- * and their values. False if the user isn't found
+ * @return array<string,string>|false|null key -> value map containing the
+ * attributes and their values. False if the user isn't found. Null if no
+ * attribute is configured
  */
  public function getExposedAttributes($uid) {
+ $exposedAttrs = $this->userManager->getExposedAttributes();
+ if (\count($exposedAttrs) === 0) {
+ return null;
+ }
+
  $userEntry = $this->userManager->getCachedEntry($uid);
  if ($userEntry === null) {
  return false;
  }
 
- $exposedAttrs = $this->userManager->getExposedAttributes();
  $attrs = [];
  foreach ($exposedAttrs as $attr) {
  $attrs[$attr] = $userEntry->getAttribute($attr);