When editing a part descriptor some of its inputs are set as required, however when editing the part in Content Studio(v 2.2.4) the inputs are ignored as required and simply allow the editor to leave the fields blank and apply anyway.
You are correct in that it’s not right to simply let user leave mandatory fields empty, but it’s not instantly obvious how this can be solved in an ideal way.
The simplest solution would be to disable the Apply button, but the content is already saved with an “invalid” part after part controller is selected, so it doesn’t make much sense. Most likely we will simply highlight blank mandatory fields inside the form (and maybe the part itself on a page, if such a part has incomplete mandatory fields).
We will discuss this on our next PAB meeting and come back with the resolution.