Add Custom Meta to products on WooCommerce

wp-woo-add-product-meta.php

<?php // Code should be on functions.php


// Display Fields
add_action( 'woocommerce_product_options_general_product_data', 'woo_add_custom_general_fields' );
// Save Fields
add_action( 'woocommerce_process_product_meta', 'woo_add_custom_general_fields_save' );


function woo_add_custom_general_fields() {

  global $woocommerce, $post; ?>
  
  <div class="options_group"> 
    
    <?php
    woocommerce_wp_text_input( 
      array( 
        'id'          => '_email_contacto', 
        'label'       => __( 'Email de Contacto', 'woocommerce' ), 
        'placeholder' => '[email protected]',
        'desc_tip'    => 'true',
        'description' => __( 'Email de contacto del dueño de la publicación', 'woocommerce' ) 
      )
    );
    ?>

  </div>

  <?php
  
}

function woo_add_custom_general_fields_save( $post_id ){
  
  // Text Field
  $woocommerce_text_field = $_POST['_email_contacto'];
  if( empty( $woocommerce_text_field ) || (is_email($_POST['_email_contacto'])) )
    update_post_meta( $post_id, '_email_contacto', esc_attr( $woocommerce_text_field ) );

}

?>