Hello,

I provided a hex package live_stream_async with which provides you with stream_async/4 macro that you can use like this:

  use LiveStreamAsync

  def mount(%{"location" => location}, _, socket) do
    {:ok,
     socket
     |> stream_async(:hotels, fn -> Hotels.fetch!(location) end)
    }
  end

I finally got around to try and implement this using start_async/3 and handle_async/3. It turns out to be rather simple to do, so perhaps it’s not worthy of a macro at all.

Because streams must be lists, I needed to add an extra assign to control whether or not the stream had been asynchronously loaded. Here’s what I did:

@impl true
def mount(%{"id" => id}, _session, socket) do
  {:ok,
   socket
   |> assign(:foos, AsyncResult.loading()),
   |> stream(:foos, [])
   |> start_async(:foos, fn ->
     Foo.list_foos(id)
   end)}
end

@impl true
def handle_async(:foos, {:ok, foos}, socket) do
  {:noreply,
   socket
   |> assign(foos: AsyncResult.ok(:ok))
   |> stream(:foos, foos, reset: true)}
end

@impl true
def render(assigns) do
  ~H"""
  <.async_result :let={_foos} assign={@foos}>
    <:loading>
      <div><%= gettext("Loading...") %></div>
    </:loading>
    <:failed :let={_failure}>
      <div><%= gettext("An error occurred.") %></div>
    </:failed>
    <.table id="foos" rows={@streams.foos}>
      ...
    </.table>
  </.async_result>
  """
end

assign_async is implemented on top of start_async and the handle_async callback. So you could use those to build your own asynchronous behavior and add to the stream in the callback.