I was writing a macro for injecting internationalised routes into MyAppWeb.Router.

When using the Gettext macros, in contrast to the Gettext functions, the msgid argument must be a string at compile-time (see docs).

I am confused about why that’s not the case here:

defmodule MyAppWeb.LocaleRoutes do
  require MyAppWeb.Gettext
  import MyAppWeb.Gettext

  @display_languages ["en", "nl", "pt", "fil", "zh"]

  defmacro __using__(_) do
    quote do
      require unquote(__MODULE__)
      import unquote(__MODULE__)
    end
  end

  defmacro live_int(path, live_view) do
    for lang <- @display_languages do
      IO.inspect(path) # For example: "welcome"
      path_int = "/#{lang}/#{Gettext.with_locale(lang, fn -> dgettext("routes", path) end)}"

      quote do
        live unquote(path_int), unquote(live_view)
      end
    end
  end

  defmacro get_int(path, plug, plug_opts) do
    for lang <- @display_languages do
      path_int = "/#{lang}/#{Gettext.with_locale(lang, fn -> dgettext("routes", path) end)}"

      quote do
        live unquote(path_int), unquote(plug), unquote(plug_opts)
      end
    end
  end
end

Gettext complains that it’s not getting a string at compile-time, but instead is getting a AST node: {:path, [line: 16, column: 81], nil}. But since the path is not user generated, but defined in MyAppWeb.Router, I expected the msgid to be a string at compile-time.