commit e0967d88df00f5bcceb8cc570eb715546ce95346
Author: Florian Best <best@univention.de>
Date:   Tue Aug 6 18:43:42 2019 +0200

    Bug #49092: prevent extended attribute to overwrite mapping of existing properties
    
    For example, there exists a extended attribute with ldapMapping=initials and CLIName=myInitials it would overwrite the mapping.
    Therefore UDM doesn't have a value for that property, e.g:
    udm users/user list --filter uid=foo | grep -i initial
      initials: None
      myInitials: A.B.
    
    After the fix:
    udm users/user list --filter uid=foo | grep -i initial
      initials: A.B.
      myInitials: None
    
    Not sure if this is the best fix. It's currently not easily possible to map
    both.

diff --git a/management/univention-directory-manager-modules/modules/univention/admin/modules.py b/management/univention-directory-manager-modules/modules/univention/admin/modules.py
index 7b73ad9622..006f691ddc 100644
--- a/management/univention-directory-manager-modules/modules/univention/admin/modules.py
+++ b/management/univention-directory-manager-modules/modules/univention/admin/modules.py
@@ -465,10 +465,18 @@ def update_extended_attributes(lo, module, position):
 		)
 
 		# add LDAP mapping
-		if attrs['univentionUDMPropertyLdapMapping'][0].lower() != 'objectClass'.lower():
-			module.mapping.register(pname, attrs['univentionUDMPropertyLdapMapping'][0], unmap_method, map_method)
+		attribute_name = attrs['univentionUDMPropertyLdapMapping'][0]
+		if attribute_name.lower() != 'objectClass'.lower():
+			already_existing_map_name = module.mapping.mapName(pname)
+			already_existing_unmap_name = module.mapping.unmapName(attribute_name)
+			if already_existing_map_name and already_existing_map_name != attribute_name:
+				pass
+			elif already_existing_unmap_name and already_existing_unmap_name != pname:
+				pass
+			else:
+				module.mapping.register(pname, attribute_name, unmap_method, map_method)
 		else:
-			module.mapping.register(pname, attrs['univentionUDMPropertyLdapMapping'][0], univention.admin.mapping.nothing, univention.admin.mapping.nothing)
+			module.mapping.register(pname, attribute_name, univention.admin.mapping.nothing, univention.admin.mapping.nothing)
 
 		if hasattr(module, 'layout'):
 			tabname = attrs.get('univentionUDMPropertyTranslationTabName;entry-%s' % lang, attrs.get('univentionUDMPropertyLayoutTabName', [_('Custom')]))[0]