From 547b72fa270b4eaa707866f61f05189328bd7064 Mon Sep 17 00:00:00 2001
From: campbell-m <87438215+campbell-m@users.noreply.github.com>
Date: Tue, 11 Jun 2024 09:56:58 +0100
Subject: [PATCH] Check that we have a valid Joomla user.  See GitHub Issue
 #3682.

---
 web/lib/MRBS/Auth/AuthJoomla.php | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/web/lib/MRBS/Auth/AuthJoomla.php b/web/lib/MRBS/Auth/AuthJoomla.php
index c668978341..f46a861107 100644
--- a/web/lib/MRBS/Auth/AuthJoomla.php
+++ b/web/lib/MRBS/Auth/AuthJoomla.php
@@ -127,8 +127,21 @@ public function getUsernames() : array
       {
         $user = Factory::getUser((int)$user_id);
       }
-      $result[] = array('username'     => $user->username,
-                        'display_name' => $user->name);
+      // Check to see that the user has a username. The result of getUser() on a user_id that doesn't exist is,
+      // strangely, a user object with all properties set to null.  In theory (?) all the user_ids returned by
+      // getUsersByGroup() should exist, but there has been a case where this is not so.  See
+      // https://github.com/meeting-room-booking-system/mrbs-code/issues/3682 .
+      if (isset($user->username))
+      {
+        $result[] = array(
+          'username' => $user->username,
+          'display_name' => $user->name
+        );
+      }
+      else
+      {
+        trigger_error("The Joomla user with id $user_id appears in Joomla groups but not in Joomla users.", E_USER_WARNING);
+      }
     }
 
     // Need to sort the users