<?php
namespace VendorModuleBlock;

use MagentoCatalogModelProductFactory;
use MagentoCatalogBlockProductAbstractProduct;
use MagentoFrameworkViewElementTemplate;
use MagentoCatalogApiProductRepositoryInterface;
use MagentoCatalogModelProduct;

class PromoteIcons extends MagentoCatalogBlockProductView {
public function getSale() {
    return "HELLO SALE";
  }
}
?>

<block class="VendorModuleBlockPromoteIcons" name="sale" as="sale" template="Vendor_Module::product/view/onsale.phtml" before="product.info.media.image" />