Direct non-captured output to the terminal (#273)

lib/livebook/runtime/elixir_standalone.ex

@@ -55,7 +55,10 @@ defmodule Livebook.Runtime.ElixirStandalone do
   defp start_elixir_node(elixir_path, node_name, eval, argv) do
     # Here we create a port to start the system process in a non-blocking way.
     Port.open({:spawn_executable, elixir_path}, [
-      :binary,
+      # We don't communicate with the system process via stdio,
+      # contrarily, we want any non-captured output to go directly
+      # to the terminal
+      :nouse_stdio,
       :hide,
       args: elixir_flags(node_name) ++ ["--eval", eval, "--" | Enum.map(argv, &to_string/1)]
     ])

lib/livebook/runtime/mix_standalone.ex

@@ -90,8 +90,10 @@ defmodule Livebook.Runtime.MixStandalone do
   defp start_elixir_mix_node(elixir_path, node_name, eval, argv, project_path) do
     # Here we create a port to start the system process in a non-blocking way.
     Port.open({:spawn_executable, elixir_path}, [
-      :binary,
-      :stderr_to_stdout,
+      # We don't communicate with the system process via stdio,
+      # contrarily, we want any non-captured output to go directly
+      # to the terminal
+      :nouse_stdio,
       :hide,
       cd: project_path,
       args:

lib/livebook/runtime/standalone_init.ex

@@ -39,7 +39,9 @@ defmodule Livebook.Runtime.StandaloneInit do
       # Minimize schedulers busy wait threshold,
       # so that they go to sleep immediately after evaluation.
       # Enable ANSI escape codes as we handle them with HTML.
-      "+sbwt none +sbwtdcpu none +sbwtdio none -elixir ansi_enabled true",
+      # Disable stdin, so that the system process never tries to read
+      # any input from the terminal.
+      "+sbwt none +sbwtdcpu none +sbwtdio none -elixir ansi_enabled true -noinput",
       # Make the node hidden, so it doesn't automatically join the cluster
       "--hidden",
       # Use the cookie in Livebook