Missing attributes on product list

Question

When displaying a product collection using a Mage_Catalog_Block_Product_List-type block, the custom attributes manufacturer and part_number are both blank/null/empty strings. Here's what's been checked so far:

1. The attributes have been added to the default product attribute set
2. The attributes have been added to the <reference name="product_list"> using the addAttribute method
3. Both attributes are set to Display in product listing in their configurations
4. The attributes are accessible via getManufacturer and getPartNumber after a product load

I have attempted some debugging (for example, I know the addAttribute method is being called), but if this is an issue anyone's run into, I would greatly appreciate some guidance.

As a side note, these two attributes do show up in some development environments, but not in what will be production. This leads me to believe that it's a configuration issue, though I don't want to influence answers down my (possibly) wrong line of thought.

Thanks

Answer 1

Adding attributes via layout XML is obselete as of CE 1.3/EE 1.8:

http://www.magentocommerce.com/wiki/4_-_themes_and_template_customization/catalog/add-attributes-to-product-grid#update_layout_xml

So, there are two ways to add to your collections:

Rewrite and Extend:

Rewrite Mage_Catalog_Block_Product_List and extend the protected method _getProductCollection to grab the parent, then add your attributes to it:

protected function _getProductCollection()
{
    $collection = parent::_getProductCollection();
    $collection->addAttributeToSelect('manufacturer')->addAttributeToSelect('part_number');

    return $collection;


}

Add to all default product collections:

Make your own module, and in the config.xml, add the following:

<?xml version="1.0"?>
<config>
    <frontend>
        <product>
            <collection>
                <attributes>
                    <manufacturer/>
                    <part_number/>
                </attributes>
            </collection>
        </product>
    </frontend>
</config>

That should add those two attributes as default members of all basis catalog collections.

Edit:

Another source of potential headaches here could be the exclusion of these attributes in various environments from the flat catalog. To include in the flat catalog, enable the following setting in Catalog > Attributes > Manage Attributes:

To ensure that the changes take place on the frontend, reindex the appropriate flat data like so:

cd {magento_root}/shell
php indexer.php --reindex catalog_product_flat
php indexer.php --reindex catalog_category_flat

Note, you may need to reindex others. See: https://www.atwix.com/magento/process-magento-indexes-from-command-line/

Answer 2

I don't believe adding product attributes via layout xml is obsolete.

<action method="addAttribute"><code>image</code></action>

Works in 1.9.1

I think the issue is probably related to having the "Used in product listing" flag set to yes.

The way Magento works, it will use the flat product table to serve category product listing data (if you have that option enabled). The attributes that go into that table are attributes with the "Used in product listing" flag set to TRUE

When you load a product individually, it uses the EAV structure, which is apathetic to that attribute setting.