I would like to know if there is any way to make the SKU field required, before publishing a new product. Otherwise, if there is no SKU, to be able to save the product only as a draft.
Maybe you can simply use this very simple code snippet to display an error message when the SKU field is empty when trying to save a the product (works for products and variations too).
If the product with an empty SKU is published, it will be saved as "DRAFT".
The code:
add_action('woocommerce_admin_process_product_object', 'mandatory_product_sku');
add_action('woocommerce_admin_process_variation_object', 'mandatory_product_sku');
function mandatory_product_sku( $product ) {
if( ! $product->get_sku( 'edit' ) ) {
$message = __( 'Caution! The SKU field is required.', 'woocommerce' );
if( $product->get_status('edit') === 'publish' ) {
$product->set_status('draft');
$message .= ' ' . __('Product has been saved as "DRAFT".', 'woocommerce' );
}
WC_Admin_Meta_Boxes::add_error( $message );
}
}
Code goes in functions.php file of the active child theme (or active theme). Tested and works.