Head.php(/app/code/core/Mage/Page/Block/Html/Head.php) (/app/code/local/Mage/Page/Block/Html/Head.php)
:
public function getRobots()
{
if (empty($this->_data['robots'])) {
$this->_data['robots'] = Mage::getStoreConfig('design/head/default_robots');
}
if(Mage::app()->getFrontController()->getAction()->getFullActionName() == 'catalog_category_view'){
$appliedFilters = Mage::getSingleton('catalog/layer')->getState()->getFilters();
if(is_array($appliedFilters) && count($appliedFilters) > 0){
$this->_data['robots'] = "NOINDEX, FOLLOW";
}
}
return $this->_data['robots'];
}
P.S. , .
Mage::app()->getFrontController()->getAction()->getFullActionName()