Check for terminal support from Elixir command line

Author: José Valim

bin/elixir

@@ -84,6 +84,10 @@ SCRIPT_PATH=$(dirname "$SELF")
 if [ "$OSTYPE" = "cygwin" ]; then SCRIPT_PATH=$(cygpath -m $SCRIPT_PATH); fi
 if [ "$MODE" != "iex" ]; then ERL="-noshell -s elixir start_cli $ERL"; fi
 
+# Check for terminal support
+test -t 1
+if [ $? = 0 ]; then ERL="-elixir ansi_enabled true $ERL"; fi
+
 if [ -z "$ERL_PATH" ]; then
   if [ -f "$SCRIPT_PATH/../releases/RELEASES" ] && [ -f "$SCRIPT_PATH/erl" ]; then
     ERL_PATH="$SCRIPT_PATH"/erl

lib/elixir/lib/io/ansi.ex

@@ -31,16 +31,14 @@ defmodule IO.ANSI do
   @doc """
   Checks if ANSI coloring is supported and enabled on this machine.
 
-  By default, ANSI is only enabled on UNIX machines. Enabling or
-  disabling ANSI escapes can be done by configuring the
-  `:ansi_enabled` value in the `:elixir` application.
+  This function simply reads the configuration value for
+  `:ansi_enabled` in the `:elixir` application. The value is by
+  default false unless Elixir can detect during startup that
+  `stdout` is a terminal.
   """
   @spec enabled? :: boolean
   def enabled? do
-    case Application.fetch_env(:elixir, :ansi_enabled) do
-      {:ok, boolean} when is_boolean(boolean) -> boolean
-      :error -> not match?({:win32, _}, :os.type())
-    end
+    Application.get_env(:elixir, :ansi_enabled, false)
   end
 
   @doc "Resets all attributes"

lib/mix/test/mix/cli_test.exs

@@ -147,8 +147,7 @@ defmodule Mix.CLITest do
 
   defp mix(args) when is_list(args) do
     System.cmd(elixir_executable,
-               ["-e", "Application.put_env(:elixir, :ansi_enabled, false)",
-                "-r", mix_executable, "--"|args],
+               ["-r", mix_executable, "--"|args],
                [stderr_to_stdout: true]) |> elem(0)
   end
 

src/elixir.app.src

@@ -7,5 +7,5 @@
  {registered, [elixir_code_server]},
  {applications, [kernel,stdlib,crypto,compiler,syntax_tools]},
  {mod, {elixir,[]}},
- {env, [{uri, #{}}]}
+ {env, [{uri, #{}},{ansi_enabled, false}]}
 ]}.