grouplib.php

    print_object($cm);
    $context = context_module::instance($cm->id);
    $aag = has_capability('moodle/site:accessallgroups', $context);
    if ($groupmode == VISIBLEGROUPS or $aag) {
        $allowedgroups = groups_get_all_groups($cm->course, 0, $cm->groupingid); // any group in grouping
    } else {
        $allowedgroups = groups_get_all_groups($cm->course, $USER->id, $cm->groupingid); // only assigned groups
    }
    print_object($allowedgroups);
    $activegroup = groups_get_activity_group($cm, true, $allowedgroups);

    $groupsmenu = array();
    if ((!$allowedgroups or $groupmode == VISIBLEGROUPS or $aag) and !$hideallparticipants and !$cm->groupmembersonly) {
        $groupsmenu[0] = get_string('allparticipants');
    }