discount based on role always 0 dollar

just found the reason, it seems $action is used on searching conditions table, so condition_list always empty:
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function uc_discounts_product_class_apply($op, $action, $total_price, &$cart) {
//print_r($cart);
// get conditions to make sure products can't be used more than once for
// a discount
$sql = "SELECT * FROM {uc_discounts_conditions} WHERE discount_id=%d ";
$sql .= "AND property='product_class' AND item_id='%s' ";
$sql .= "ORDER BY condition_group, weight";
$result = db_query($sql, $action->discount_id, $action->item_id);
$condition_list = array();
while ($row = db_fetch_object($result)) {
$condition_list[$row->id] = $row;
}
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after following changes, everything works fine:

$sql = "SELECT * FROM {uc_discounts_conditions} WHERE discount_id=%d ";
//$sql .= "AND property='product_class' AND item_id='%s' ";
$sql .= "ORDER BY condition_group, weight";
$result = db_query($sql, $action->discount_id);