Why did Wordpress cut out the form tag when inserting a shortcode?

Question

WordPress

add_action( 'woocommerce_single_variation', 'product_mail', 11 );
function product_mail(){
    echo "<div class='mail-form-wrap'>".do_shortcode("[mailpoet_form id='1']")."</div>";

}

Answer 1

Because you are trying to nest a form within a form, here you hang your form
https://github.com/woocommerce/woocommerce/blob/aa...
but if you look at line 28, you will see that the form is already open there