I’ve wanted this before but my general thoughts are:

• If it’s a simple check with short blocks I don’t mind the negation, as in your example, or simply using the <%= %> syntax.
• If there are larger blocks I prefer to extract to function components and do the conditional via a match as I don’t enjoy reading long if/else in templates, ie:

  defp component(%{role: :admin} = assigns), do: ~H""
  defp component(assigns), do: ~H""
  

• The number of times I need an else is quite low compared to lone ifs (this is, of course, just me)
• This last one is pure speculation as I’ve never studied HEEx’s source, but else would have to be aware of its immediate previous sibling and I don’t believe there is precedent for this (closest would be slots checking they are not in other slots). I can imagine this being deemed not worth taking on unless there was overwhelming demand for it.

Having said all that if it were available I would use it, I just don’t personally want it that badly so have never bothered to bring it up myself.

I generally prefer this form. Part of the whole appeal of structured programming is that program structure dictates flow, so you do not have to scan through lines of code before knowing if they will be executed.

Conversely, the above is structure-less, and requires you check after reading any :if element if the next element is an :else to fully understand the output.

What makes HEEX different to Vue’s syntax is the fact that Vue doesn’t have the <% %> so it needs to have :else