Hi,

Are there any preferred ways of checking for feature flags for live views in a live_session?

I would assume that one use attach_hook/4 and then add that hook to the relevant live_session.

I know Plausible.io uses FunWithFlags making it a nice reference, but they do this for controller actions and components, not entire live views.

I threw (!) together the code below to test the concept.

It gets more complicated if one has a tab for a path to several other live views of course, which I would believe is a fairly common use case.

defmodule MyAppWeb.CheckFlags do
  use MyAppWeb, :verified_routes
  import Phoenix.LiveView
  import MyAppWeb.Gettext

  def on_mount(:default, _params, _session, socket) do
    {:cont,
     socket
     |> attach_hook(:flags, :handle_params, &check_flags/3)}
  end

  defp check_flags(_params, _session, socket) do
    continue? =
      case socket.view do
        MyAppWeb.ExcitingExperimentalFeatureLive ->
          FunWithFlags.enabled?(:exciting_experimental_feature, for: socket.assigns.current_user)

        _ ->
          true
      end

    if continue? do
      {:cont, socket}
    else
      socket =
        socket
        |> Phoenix.LiveView.put_flash(
          :error,
          gettext("This feature has not been enabled for your account.")
        )
        |> Phoenix.LiveView.redirect(to: ~p"/")

      {:halt, socket}
    end
  end
end