Is there a way to disable the <nolink> option for menu links?

Question

For our unified Drupal platform, we require all of our sites main menu items to be a page and any sub-pages to show a path following the parent menu item. So if "About Us" (with a path of /about-us) is a top level menu item, it must be a page. And the page "History" under that will have a path of /about-us/history. "About Us" cannot be a <nolink> with History as a child. How can I prevent users from using the <nolink> option for menu links? The core link module includes in the description to the user of how to include the <nolink> option. That shows that if it supports internal and external links. Well, I don't want to exclude one of those for menu links in general. I'm thinking I'm going to have to do a form alter, plus some type of validation, but I'm not sure what.

It was added from this issue but they did not do a toggle the way the D7 link contrib module did. And it's a toggle I need - to turn it off in this case.

Answer 1

I'd say that I would solve this requirement by doing three things:

1. CSS: easy one, just hide the tooltip about
2. JavaScript: add a client-side validation that checks the value of the link field and if the '' regexp is found, prevent from saving and show a message.
3. hook_form_alter and check for instance via route parameters if it has menu_link_content and then add your server-side validation.

Also, point 1 could be done as well in the form_alter by replacing the description there instead of via CSS.