Cadastrar campos na tela de registro.

/*
 * Validate the extra register fields.
 *
 * @param WP_Error $validation_errors Errors.
 * @param string   $username          Current username.
 * @param string   $email             Current email.
 *
 * @return WP_Error
 */
function wooc_validate_extra_register_fields( $errors, $username, $email ) {
    if ( isset( $_POST['billing_first_name'] ) && empty( $_POST['billing_first_name'] ) ) {
        $errors->add( 'billing_first_name_error', __( '<strong>Error</strong>: First name is required!', 'woocommerce' ) );
    }
    if ( isset( $_POST['billing_last_name'] ) && empty( $_POST['billing_last_name'] ) ) {
        $errors->add( 'billing_last_name_error', __( '<strong>Error</strong>: Last name is required!.', 'woocommerce' ) );
    }
    if ( isset( $_POST['billing_phone'] ) && empty( $_POST['billing_phone'] ) ) {
        $errors->add( 'billing_phone_error', __( '<strong>Error</strong>: Phone is required!.', 'woocommerce' ) );
    }
    if ( isset( $_POST['billing_cpf'] ) && empty( $_POST['billing_cpf'] ) ) {
        $errors->add( 'billing_cpf_error', __( '<strong>Error</strong>: CPF is required!.', 'woocommerce' ) );
    }
    if ( isset( $_POST['googleplus'] ) && empty( $_POST['googleplus'] ) ) {
        $errors->add( 'googleplus_error', __( '<strong>Error</strong>: facebook is required!.', 'woocommerce' ) );
    }
    return $errors;
}
add_filter( 'woocommerce_registration_errors', 'wooc_validate_extra_register_fields', 10, 3 );


/*
SALVANDO
 */
function wooc_save_extra_register_fields( $customer_id ) {
    if ( isset( $_POST['billing_first_name'] ) ) {
        // WordPress default first name field.
        update_user_meta( $customer_id, 'first_name', sanitize_text_field( $_POST['billing_first_name'] ) );
        // WooCommerce billing first name.
        update_user_meta( $customer_id, 'billing_first_name', sanitize_text_field( $_POST['billing_first_name'] ) );
    }
    if ( isset( $_POST['billing_last_name'] ) ) {
        // WordPress default last name field.
        update_user_meta( $customer_id, 'last_name', sanitize_text_field( $_POST['billing_last_name'] ) );
        // WooCommerce billing last name.
        update_user_meta( $customer_id, 'billing_last_name', sanitize_text_field( $_POST['billing_last_name'] ) );
    }
    if ( isset( $_POST['billing_phone'] ) ) {
        // WooCommerce billing phone
        update_user_meta( $customer_id, 'billing_phone', sanitize_text_field( $_POST['billing_phone'] ) );
    }
    if ( isset( $_POST['billing_cpf'] ) ) {
        // WooCommerce billing phone
        update_user_meta( $customer_id, 'billing_cpf', sanitize_text_field( $_POST['billing_cpf'] ) );
    }
    if ( isset( $_POST['googleplus'] ) ) {
        // WooCommerce billing phone
        update_user_meta( $customer_id, 'googleplus', sanitize_text_field( $_POST['googleplus'] ) );
    }
}
add_action( 'woocommerce_created_customer', 'wooc_save_extra_register_fields' );