Check commerce modules exist

Function at_commerce_css_alter does not check the existence of other commerce module, when any/many of these modules are not enabled it causes drupal to recursively check for the files many times leading to a tremendous performance impact. In my case I have none of the commerce modules and over 900ms was being spent in searching these non existent commerce modules on every page load.

Below is the patched code which simple adds a check for each depended module before fetching their paths, saving performance degradation.

/**
  * Implements hook_css_alter().
  */
 function at_commerce_css_alter(&$css) {
 
   // Replace all Commerce module CSS files with our own for total control over all        styles.
   // Commerce module uses the BAT CSS file naming convention (base, admin, theme).
   $path = drupal_get_path('theme', 'at_commerce');
 
   // cart
   if (module_exists('commerce_cart')){
       $cart_theme = drupal_get_path('module', 'commerce_cart') . '/theme/commerce_cart.   theme.css';
       if (isset($css[$cart_theme])) {
         $css[$cart_theme]['data'] = $path . '/css/commerce/commerce_cart.theme.css';
         $css[$cart_theme]['group'] = 1;
       }
   }
 
   // checkout
   if (module_exists('commerce_checkout')){
       $checkout_base  = drupal_get_path('module', 'commerce_checkout') . '/theme/         commerce_checkout.base.css';
       $checkout_admin = drupal_get_path('module', 'commerce_checkout') . '/theme/         commerce_checkout.admin.css';
       $checkout_theme = drupal_get_path('module', 'commerce_checkout') . '/theme/         commerce_checkout.theme.css';
       if (isset($css[$checkout_base])) {
         $css[$checkout_base]['data'] = $path . '/css/commerce/commerce_checkout.base.     css';
         $css[$checkout_base]['group'] = 1;
       }
       if (isset($css[$checkout_admin])) {
         $css[$checkout_admin]['data'] = $path . '/css/commerce/commerce_checkout.admin.   css';
         $css[$checkout_admin]['group'] = 1;
       }
       if (isset($css[$checkout_theme])) {
         $css[$checkout_theme]['data'] = $path . '/css/commerce/commerce_checkout.theme.   css';
         $css[$checkout_theme]['group'] = 1;
       }
   }
 
   // customer
   if (module_exists('commerce_customer')){
       $customer_admin = drupal_get_path('module', 'commerce_customer') . '/theme/         commerce_customer.admin.css';
       if (isset($css[$customer_admin])) {
         $css[$customer_admin]['data'] = $path . '/css/commerce/commerce_customer.admin.   css';
         $css[$customer_admin]['group'] = 1;
       }
   }
 
   // file (contrib)
   if (module_exists('commerce_file')){
       $file_forms = drupal_get_path('module', 'commerce_file') . '/theme/commerce_file.   forms.css';
       if (isset($css[$file_forms])) {
         $css[$file_forms]['data'] = $path . '/css/commerce/commerce_file.forms.css';
         $css[$file_forms]['group'] = 1;
       }
   }
 
   // line items
   if (module_exists('commerce_line_item')){
       $line_item_admin = drupal_get_path('module', 'commerce_line_item') . '/theme/       commerce_line_item.admin.css';
       $line_item_theme = drupal_get_path('module', 'commerce_line_item') . '/theme/       commerce_line_item.theme.css';
       if (isset($css[$line_item_admin])) {
         $css[$line_item_admin]['data'] = $path . '/css/commerce/commerce_line_item.admin. css';
         $css[$line_item_admin]['group'] = 1;
       }
       if (isset($css[$line_item_theme])) {
         $css[$line_item_theme]['data'] = $path . '/css/commerce/commerce_line_item.theme. css';
         $css[$line_item_theme]['group'] = 1;
       }
   }

   // order
   if (module_exists('commerce_order')){
       $order_admin = drupal_get_path('module', 'commerce_order') . '/theme/               commerce_order.admin.css';
       $order_theme = drupal_get_path('module', 'commerce_order') . '/theme/               commerce_order.theme.css';
       if (isset($css[$order_admin])) {
         $css[$order_admin]['data'] = $path . '/css/commerce/commerce_order.admin.css';
         $css[$order_admin]['group'] = 1;
       }
       if (isset($css[$order_theme])) {
         $css[$order_theme]['data'] = $path . '/css/commerce/commerce_order.theme.css';
         $css[$order_theme]['group'] = 1;
       }
   }
 
   // payment
   if (module_exists('commerce_payment')){
       $payment_admin = drupal_get_path('module', 'commerce_payment') . '/theme/           commerce_payment.admin.css';
       $payment_theme = drupal_get_path('module', 'commerce_payment') . '/theme/           commerce_payment.theme.css';
       if (isset($css[$payment_admin])) {
         $css[$payment_admin]['data'] = $path . '/css/commerce/commerce_payment.admin.     css';
         $css[$payment_admin]['group'] = 1;
       }
       if (isset($css[$payment_theme])) {
         $css[$payment_theme]['data'] = $path . '/css/commerce/commerce_payment.theme.     css';
         $css[$payment_theme]['group'] = 1;
       }
   }
 
   // price
   if (module_exists('commerce_price')){
       $price_theme = drupal_get_path('module', 'commerce_price') . '/theme/               commerce_price.theme.css';
       if (isset($css[$price_theme])) {
         $css[$price_theme]['data'] = $path . '/css/commerce/commerce_price.theme.css';
         $css[$price_theme]['group'] = 1;
       }
   }
 
   // product
   if (module_exists('commerce_product')){
       $product_admin = drupal_get_path('module', 'commerce_product') . '/theme/           commerce_product.admin.css';
       $product_theme = drupal_get_path('module', 'commerce_product') . '/theme/           commerce_product.theme.css';
       if (isset($css[$product_admin])) {
         $css[$product_admin]['data'] = $path . '/css/commerce/commerce_product.admin.     css';
         $css[$product_admin]['group'] = 1;
       }
       if (isset($css[$product_theme])) {
         $css[$product_theme]['data'] = $path . '/css/commerce/commerce_product.theme.     css';
         $css[$product_theme]['group'] = 1;
       }
   }
 
   // tax
   if (module_exists('commerce_tax')){
       $tax_admin = drupal_get_path('module', 'commerce_tax') . '/theme/commerce_tax.      admin.css';
       $tax_theme = drupal_get_path('module', 'commerce_tax') . '/theme/commerce_tax.      theme.css';
       if (isset($css[$tax_admin])) {
         $css[$tax_admin]['data'] = $path . '/css/commerce/commerce_tax.admin.css';
         $css[$tax_admin]['group'] = 1;
       }
       if (isset($css[$tax_theme])) {
         $css[$tax_theme]['data'] = $path . '/css/commerce/commerce_tax.theme.css';
         $css[$tax_theme]['group'] = 1;
       }
   }
 }