以下是我最终为感兴趣的人使用的代码：

/* This snippet removes the action that inserts thumbnails to products in the loop
 * and re-adds the function customized with our wrapper in it.
 * It applies to all archives with products.
 *
 * @original plugin: WooCommerce
 * @author of snippet: Brian Krogsard
 */

remove_action( \'woocommerce_before_shop_loop_item_title\', \'woocommerce_template_loop_product_thumbnail\', 10);
add_action(    \'woocommerce_before_shop_loop_item_title\', \'woocommerce_template_loop_product_thumbnail\', 10);

/**
 * WooCommerce Loop Product Thumbs
 **/

 if ( ! function_exists( \'woocommerce_template_loop_product_thumbnail\' ) ) {
    function woocommerce_template_loop_product_thumbnail() {
        echo woocommerce_get_product_thumbnail();
    } 
 }

/**
 * WooCommerce Product Thumbnail
 **/

 if ( ! function_exists( \'woocommerce_get_product_thumbnail\' ) ) {

    function woocommerce_get_product_thumbnail( $size = \'shop_catalog\', $placeholder_width = 0, $placeholder_height = 0  ) {
        global $post, $wp_query, $woocommerce, $attributes;
        // if ( ! $placeholder_width ) {
        //  $placeholder_width = $woocommerce->get_image_size( \'shop_catalog_image_width\' );
        // }
        // if ( ! $placeholder_height ){
        //  $placeholder_height = $woocommerce->get_image_size( \'shop_catalog_image_height\' );
        // }

        $output = \'<div class="imagewrapper">\';
        if ( has_post_thumbnail() ) {

            $output .= get_the_post_thumbnail( $post->ID, $size ); 

        } else {

            $output .= \'<img src="\'. woocommerce_placeholder_img_src() .\'" alt="Placeholder" width="\' . $placeholder_width . \'" height="\' . $placeholder_height . \'" />\';

        }

        //$product .=  wc_get_product($post->ID ) ;
        //$name .= $product->get_name();

        $output .= \'<div class="sizeAvailHover">\';
        //$output .= $name;
        //$product .=  wc_get_product($post->ID ) ;
        $product = wc_get_product( $wp_query->post );


        //echo get_post_format();

            // echo \'total stock : \';
            // echo $product->is_in_stock();



        if ( $product->is_type( \'variable\' ) ) {
            // $attributes .= $product->list_attributes();
            // echo print_r($attributes);
            // $attributes = $product->get_attributes();
            // echo print_r($attributes);
            // $attributes .= $product->wc_display_product_attributes();
            // echo print_r($attributes);
            // $attributes .= $product->get_variation_attributes();
            // echo print_r($attributes);


            if($product->is_in_stock()) {
                $output .= \' Available sizes: <br/>\';
                $variations = $product->get_available_variations();
                $i = 0;
                foreach($variations as $variation){
                    $variation_id = $variation[\'variation_id\'];
                    $variation_obj = new WC_Product_variation($variation_id);
                    $stock = $variation_obj->get_stock_quantity();
                    //echo $stock;
                    // echo \'--\';
                    //echo $variation_obj->get_sku();
                    //echo print_r($variation_obj->get_variation_attributes());
                    $dummy = $variation_obj->get_variation_attributes();
                    //echo gettype($stock);
                    if ((is_int($stock) || ctype_digit($stock)) && (int)$stock > 0 ) { // int }
                    //if ($stock > 0 ) {
                        //echo $variation_obj->get_attributes();
                        //echo \'yesssss\';
                        // echo print_r($dummy[\'attribute_pa_size\']);
                        $output .= \'<span class="availSize">\' . strtoupper($dummy[\'attribute_pa_size\']) . \'</span>\';
                    } else {
                        // echo print_r($dummy[\'attribute_pa_size\']);
                        $output .= \'<span class="unavailSize">\' . strtoupper($dummy[\'attribute_pa_size\']) . \'</span>\';
                    }
                    if(++$i !== count($variations)) {
                        $output .= \', \';
                    }

                    //echo \'<br/>\';

                }
            } else {
                $output .= \' Sold out<br/>Notify me when the product is back in stock\';
            }


            // if ( ! $attributes ) {
            //     echo "No attributes";
            // }
            // foreach ( $attributes as $attribute ) {

         //        echo $attribute[\'name\'] . ": ";
         //        $product_attributes = array();
         //        $product_attributes = explode(\'|\',$attribute[\'value\']);

         //        $attributes_dropdown = \'<select>\';

         //        foreach ( $product_attributes as $pa ) {
         //            $attributes_dropdown .= \'<option value="\' . $pa . \'">\' . $pa . \'</option>\';
         //        }

         //        $attributes_dropdown .= \'</select>\';

         //        echo $attributes_dropdown;
            // }
        }

        $output .= \'</div>\';

        $output .= \'</div>\';

        return $output;
    }
 }