Code-Snippets-Functions/Execute a function on a child site/WooCommerce/prevent-admin-from-adding-out-of-stock-products-into-manual-orders.txt

add_filter( 'woocommerce_ajax_add_order_item_validation', 'wc_woocommerce_ajax_add_order_item_validation', 10, 2 );
function wc_woocommerce_ajax_add_order_item_validation( $validation_error, $product ) {
    if ( $validation_error && !$product->is_in_stock() ) {
        $validation_error->add( 'product-out-of-stock', __('Product Out of Stock', 'woocommerce') );
    }
    return $validation_error;
}