What file or action causes attributes to be added to cart

Working on upgrading a 1.3.9h to 1.5.1 site

Merged custom files into 1.5.1 versions

This site has custom code that displays attributes on the product listing page

In the 1.3.9h site adding to cart from the product listing page yields a correct add to cart with correct price

In the 1.5.1 site - adding to cart from the product listing page yields a product added BUT $0.00 as the cost

Modifications originally were added to the column-grid product listing plugin

No other plugins except for this custom code which is not a plugin available

Relevent code block change in /includes/modules/product_listing.php

        if (isset($_GET['manufacturers_id'])) {
          $lc_text = '<h3 class="itemTitle"><a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), 'products_id=' . $listing->fields['products_id']) . '">' . $listing->fields['products_name'] . '</a></h3><div class="listingDescription">' . zen_trunc_string(zen_clean_html(stripslashes(zen_get_products_description($listing->fields['products_id'], $_SESSION['languages_id']))), PRODUCT_LIST_DESCRIPTION);
			
			require($template->get_template_dir('/tpl_modules_attributes_listing.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_modules_attributes_listing.php');
			
			$lc_text .= '</div>' ;
			
        } else {
          $lc_text = '<h3 class="itemTitle"><a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), ($_GET['cPath'] > 0 ? 'cPath=' . $_GET['cPath'] . '&' : '') . 'products_id=' . $listing->fields['products_id']) . '">' . $listing->fields['products_name'] . '</a></h3><div class="listingDescription">' . zen_trunc_string(zen_clean_html(stripslashes(zen_get_products_description($listing->fields['products_id'], $_SESSION['languages_id']))), PRODUCT_LIST_DESCRIPTION);

			require($template->get_template_dir('/tpl_modules_attributes_listing.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_modules_attributes_listing.php');
				
			$lc_text .= '</div>' ;

Can provide additional data if I knew what to provide

The shopping cart class processes submitted POST parameters and adds the products and selected attributes to the cart, and is triggered by the main_cart_actions.php and extra_cart_actions folder scripts if any. Of course that all depends on the submitted FORM containing all the correct fields and values, so templates must be working properly too (valid HTML, not incorrectly nested, etc).

Thank you for your response

Exactly where is the file main_cart_actions.php

Last time I looked it was in the /includes/ folder.

Duh!!! directly under /includes - - - I was looking in folders

Very little difference between 1.3.9h and 1.5.1

There are no extra_cart_actions files