allow embedded runtime by env

[ByeongUkChoi]

#1082

• add environment variable LIVEBOOK_EMBEDDED_RUNTIME_ENABLED
• hide runtime settings embedded button when LIVEBOOK_EMBEDDED_RUNTIME_ENABLED is not true

[josevalim]

Thank you! We should also check somewhere internally that, if someone tries to start the embedded runtime and it is disabled, perhaps by hacking around the UI, we fail to start it. @jonatanklosko, where would be the best place to check it?

[jonatanklosko]

where would be the best place to check it?

We have a separate LV for configuring each runtime, and that's where we connect, so we can just have a check in mount verifying that the given runtime is in fact in the runtime_module list, and raise/redirect otherwise?

[ByeongUkChoi]

@jonatanklosko

check in mount

like this?

defmodule LivebookWeb.SessionLive.ElixirStandaloneLive do

  def mount(param, session, socket) do
    unless __MODULE__ in Livebook.Config.runtime_modules() do
      raise "now allow runtime elixir standalone."

      # code...
    end
  end
end

[jonatanklosko]

@ByeongUkChoi yup, except we want to check for Livebook.Runtime.ElixirStandalone, rather than the LV __MODULE__ :)

[jonatanklosko]

@ByeongUkChoi thank you! :)