Program: 69286
Project: 69286
Buggy source:
public static int doInvitationLogin(String invitationToken,UserRequest ureq,Locale locale){
  InvitationDAO invitationDao=CoreSpringFactory.getImpl(InvitationDAO.class);
  boolean hasPolicies=invitationDao.hasInvitations(invitationToken,new Date());
  if (!hasPolicies) {
    return LOGIN_DENIED;
  }
  UserManager um=UserManager.getInstance();
  BaseSecurity securityManager=BaseSecurityManager.getInstance();
  GroupDAO groupDao=CoreSpringFactory.getImpl(GroupDAO.class);
  Invitation invitation=invitationDao.findInvitation(invitationToken);
  if (invitation == null) {
    return LOGIN_DENIED;
  }
  Identity identity=um.findIdentityByEmail(invitation.getMail());
  if (identity != null) {
    SecurityGroup allUsers=securityManager.findSecurityGroupByName(Constants.GROUP_OLATUSERS);
    if (securityManager.isIdentityInSecurityGroup(identity,allUsers)) {
      return LOGIN_DENIED;
    }
 else {
      if (!groupDao.hasRole(invitation.getBaseGroup(),identity,GroupRoles.invitee.name())) {
        groupDao.addMembershipTwoWay(invitation.getBaseGroup(),identity,GroupRoles.invitee.name());
        DBFactory.getInstance().commit();
      }
      int result=doLogin(identity,BaseSecurityModule.getDefaultAuthProviderIdentifier(),ureq);
      if (ureq.getUserSession().getRoles().isInvitee()) {
        return result;
      }
      return LOGIN_DENIED;
    }
  }
  Collection<String> supportedLanguages=I18nModule.getEnabledLanguageKeys();
  if (locale == null || !supportedLanguages.contains(locale.toString())) {
    locale=I18nModule.getDefaultLocale();
  }
  Identity invitee=invitationDao.createIdentityFrom(invitation,locale);
  return doLogin(invitee,BaseSecurityModule.getDefaultAuthProviderIdentifier(),ureq);
}

Fixed version (ground truth):
public static int doInvitationLogin(String invitationToken,UserRequest ureq,Locale locale){
  InvitationDAO invitationDao=CoreSpringFactory.getImpl(InvitationDAO.class);
  boolean hasPolicies=invitationDao.hasInvitations(invitationToken,new Date());
  if (!hasPolicies) {
    return LOGIN_DENIED;
  }
  UserManager um=UserManager.getInstance();
  BaseSecurity securityManager=BaseSecurityManager.getInstance();
  GroupDAO groupDao=CoreSpringFactory.getImpl(GroupDAO.class);
  Invitation invitation=invitationDao.findInvitation(invitationToken);
  if (invitation == null) {
    return LOGIN_DENIED;
  }
  Identity identity=um.findIdentityByEmail(invitation.getMail());
  if (identity != null) {
    SecurityGroup allUsers=securityManager.findSecurityGroupByName(Constants.GROUP_OLATUSERS);
    if (securityManager.isIdentityInSecurityGroup(identity,allUsers)) {
      return LOGIN_DENIED;
    }
 else {
      if (!groupDao.hasRole(invitation.getBaseGroup(),identity,GroupRoles.invitee.name())) {
        groupDao.addMembershipTwoWay(invitation.getBaseGroup(),identity,GroupRoles.invitee.name());
        DBFactory.getInstance().commit();
      }
      int result=doLogin(identity,BaseSecurityModule.getDefaultAuthProviderIdentifier(),ureq);
      if (ureq.getUserSession().getRoles().isInvitee()) {
        return result;
      }
      return LOGIN_DENIED;
    }
  }
  Collection<String> supportedLanguages=CoreSpringFactory.getImpl(I18nModule.class).getEnabledLanguageKeys();
  if (locale == null || !supportedLanguages.contains(locale.toString())) {
    locale=I18nModule.getDefaultLocale();
  }
  Identity invitee=invitationDao.createIdentityFrom(invitation,locale);
  return doLogin(invitee,BaseSecurityModule.getDefaultAuthProviderIdentifier(),ureq);
}