Background

I have created a fresh Phoenix app using mix phx.new.web web_interface --no-dashboard --no-ecto --no-gettext --no-mailer inside an Umbrella app.

After following the basic installation instructions for the dependencies and changing my application.ex to:

defmodule WebInterface.Application do
  use Application

  alias Desktop
  alias WebInterface.{Endpoint, Telemetry, PubSub}
  alias WebInterface.Live.MenuBar

  @impl true
  def start(_type, _args) do
    children = [
      Telemetry,
      {Phoenix.PubSub, name: PubSub},
      Endpoint,
      {Desktop.Window,
       [
         app: :web_interface,
         id: WebInterface,
         title: "Market Manager",
         size: {940, 980},
         menubar: MenuBar,
         icon: "static/images/resized_logo_5_32x32.png",
         url: &WebInterface.Endpoint.url/0
       ]}
    ]

    opts = [strategy: :one_for_one, name: WebInterface.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # boilerplate code bellow
end

I was able to launch my Desktop application and have it working.

Problem

However, after changing endpoint.ex following the instruction #3 here:

• https://github.com/elixir-desktop/desktop/blob/main/guides/your_first_app.md

I was no longer able to launch the application due to an error:

08:30:14.411 [notice] Application runtime_tools exited: :stopped
** (Mix) Could not start application web_interface: WebInterface.Application.start(:normal, []) returned an error: shutdown: failed to start child: WebInterface.Endpoint
    ** (EXIT) an exception was raised:
        ** (UndefinedFunctionError) function Phoenix.Endpoint.Supervisor.url/1 is undefined or private
            (phoenix 1.7.2) Phoenix.Endpoint.Supervisor.url(WebInterface.Endpoint)
            (phoenix 1.7.2) lib/phoenix/config.ex:65: Phoenix.Config.cache/3
            (web_interface 2.2.0) lib/web_interface/endpoint.ex:2: WebInterface.Endpoint.url/0
            (phoenix 1.7.2) lib/phoenix/endpoint/supervisor.ex:425: Phoenix.Endpoint.Supervisor.log_access_url/2
            (phoenix 1.7.2) lib/phoenix/endpoint/supervisor.ex:17: Phoenix.Endpoint.Supervisor.start_link/3
            (stdlib 4.1.1) supervisor.erl:414: :supervisor.do_start_child_i/3
            (stdlib 4.1.1) supervisor.erl:400: :supervisor.do_start_child/2
            (stdlib 4.1.1) supervisor.erl:384: anonymous fn/3 in :supervisor.start_children/2

To me, this indicates that changing Phoenix.Endpoint to Desktop.Endpoint is no longer necessary.

Question

1. Is the documentation outdated?
2. If not, am I missing something? Given that before the change the application worked, what could be causing the issue (assuming the change is indeed necessary)?

It is worth noting however, that the creation of Phoenix projects inside Umbrella applications is currently bugged (see: Phoenix 1.7 welcome page assets not showing properly) but I don’t think this is related.