Forwarding requests to LiveView

Hi @SophieDeBenedetto!

Unfortunately LiveView cannot be mounted on a separate router which is then forwarded to. The reason is that LiveView does route lookups and we currently don’t store the “forwarding path”.

There is an OK-ish solution to this problem which is to encapsulate the routes in a macro:

defmodule AdminRoutes do
  defmacro __using__(opts) do
    quote do
      scope unquote(opts) do
        live ...
      end
  end
end

And then in the router you can do:

use AdminRoutes, path: "/admin"

Another issue with mounting a LiveView in an external application is that you also need to define a socket in the endpoint. We were discussing some options to make the whole process easier but we haven’t reached a conclusion yet.

Thanks for the response! Yep after digging into the source code I can see the problem. I’ll lay it out below from anyone else who might find this helpful:

• phoenix_live_view.js implements the bindNav function which sends an event to LiveView’s channel with the URL from window.location.href. At this point, that href is the forward mounted route, in my case containing the path /admin/railway-ipc/published_messages
• The channel handles this event by calling PhoenixLive.Utils.live_link_info!/3 with that URL.
• This in turn calls Phoenix.Router.route_info/4 where the router argument is the router to which we are forwarding, in my case the router that mounts the LiveView (RailwayUiWeb.Router), and the path argument is the path from the URI, /admin/railway-ipc/published_messages. Since that router implements a route for just /published_messages, not /admin/railway-ipc/published_messages, this raises the error I reported above.

I will definitely play around with your suggestion and see where it gets me. Thanks again!

for the latest version of Phoenix, is this still the case? or there are better solutions around?

I am forwarding to a live route in another umbrella app and received the same errors.

I think I just ran into the same problem. So I found the super ugly solution to just hack the path_info in the conn:

  pipeline :routerscope do
    plug :rescoper
  end

  scope "/subapp", Subapp do
    pipe_through [:browser, :routerscope]
    forward "/", Router
  end

  def rescoper(conn, [] = _opts) do
    %{conn | path_info: [Enum.at(conn.path_info, 0)] ++ conn.path_info}
  end

This works. How can it be done in a nicer way?