UX: Prevent last child from being deleted?

E.g. take a list node. When you delete the last child, it's no longer clear to the user they are working with a list node. If I could prevent the deletion of the last remaining node (instead keep just an empty one) this would probably feel better to the user.

Implementation ideas:

• allow_empty definition for node_array prop
  • when true then each time a node_array is manipulated it in the ops, it will auto-fill an empty default
  • e.g. if you created a list node with an empty list_items array it would auto fill.
  • or alternatively: throw when that invariant is violated before commiting a transaction
• another approach would be not to touch the data layer (empty node_arrays are allowed) but just forbid the actions that could make it empty (user input) e.g. when you have the node cursor after the last item and press backspace, or when the last item is an empty text element and you have the text cursor there and press backspace (this would also lead to an empty list.list_items)

Downsides:

• Creates some special edge cases data-model wise

Priority: Low, lets see if users really struggle with this.

No files, tests, or entry points are named. Compare the proposed data-layer invariant with forbidding the user actions that empty a node array, then define the desired behavior and verify that deleting the last child still leaves the list node clear to the user.