I gave it my best shot this morning during a livestream before work and unfortunately, just couldn’t get a working solution.

Without render_existing/3, we can no longer determine whether a template exists. Depending on deployment strategies, the filesystem is sometimes no longer available.

Unfortunately, function_exported?/3 doesn’t fill the gap since render/3 will always be exported.

This means the only options would be

• writing and maintaining hundreds and hundreds of meta functions throughout the application
• crawling the filesystem at compile time to create a list of all existing template names
• using try and rescue on every page load
• some kind of macro wizardry I haven’t yet been able to think of

The idea is moving to function components over templates. Function components are a lot more flexible than templates and given they’re based on (differently named) functions there’s less phoenix magic needed – magic the phoenix teams seems to like to get away from. But not everybody will jump on board of restructing their projects immediately, therefore I feel the deprecation was a bit premature.

You’d replace your code with something like this:

<%= if function_exported?(view_module(@conn), :meta 1), do: view_module(@conn).meta(Map.merge(assigns, %{template: view_template(@conn)}), else: meta(assigns) %>

# LayoutView
def meta(assigns) do
  ~H"""
  …
  """
end

# OtherView
def meta(%{template: "index.html"} = assigns) do
  ~H"""
  …
  """
end

…

From those meta functions you can also call your existing templates using:

render("_meta.#{assigns.template}", assigns)

I looked at the docs before creating this thread. It’s because the examples provided weren’t applicable to my use case that I asked here in the first place.

I’ve found that _meta.foo.html files for simpler cases and defining a render("_meta.foo.html", assigns) functions in the view for more complex cases a very useful pattern.