How to disable search by SKU (for specific store)?

Question

For a specific store i want an remove search results, if search query matches our SKU pattern.

1. disable "searchable" in attribute config is no solution
2. rewrite core files is not wanted

So, what i need is an event which let me manipulate the search query or product collection for search result page.

I tried following events.

1. catalogsearch_searchable_attributes_load_after ... not triggered
2. catalogsearch_query(_load_before/after) ... also not triggered
3. and some others ... ;)

... but without success.

Working solutions so far ... using catalog_product_collection_load_before with following observer:

public function test(Varien_Event_Observer $observer)
{
    // some logic for check current store
    // ...

    $action = Mage::app()->getFrontController()->getAction()->getFullActionName();
    if ($action === 'catalogsearch_result_index') {
        $query = Mage::app()->getRequest()->getParam('q');
        if (preg_match("/my regex/", $query)) {
            // force empty collection with invalid entity_id
            $observer->getCollection()->addFieldToFilter('entity_id', false);
        }
    }
}

.but this looks like an ugly hack to me and shouldn't be final.

Hope you have some better approaches - maybe an more suitable event, that's no triggered for every product collection?

Update 1:

Regex check isn't really good, because partial search still works.

Preferred solution would be to disable SKU from searchable fields without disbale it globally from attribute configuration.

Update 2:

Instead of using regex i switched over to this, because it seems more correct if sku pattern is part of name/description/... and sould be searchable:

$observer->getCollection()->addFieldToFilter('sku', array('nlike' => "%{$query}%"));

Answer 1

Since there is no event like catalogsearch_result_product_collection_load_before my solution affects every product collection on searchresult page (bestsellers in sidebar, new products ...).

Thanks to Marius I found a good solution.

I changed event to controller_action_layout_render_before_catalogsearch_result_index

and Observer.php to:

const RESULT_BLOCK_NAME = 'search_result_list';
public function test($observer)
{
    if (Mage::getStoreConfigFlag('catalog/frontend/disable_sku_search')) {
        /** @var Mage_Catalog_Block_Product_List $block */
        $block = Mage::app()->getLayout()->getBlock(self::RESULT_BLOCK_NAME);
        if ($block) {
            if ($collection = $block->getLoadedProductCollection()) {
                $query = Mage::app()->getRequest()->getParam('q');
                $collection->addFieldToFilter('sku', array('nlike' => "%{$query}%"));
            }
        }
    }
}

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^{Download: https://github.com/sreichel/magento-StackExchange_DisableSearchBySku}