console: auto-detect color support by default

This makes Node pretty-print objects with color by default
when `console.log()`-ing them.

PR-URL: nodejs#19372
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: addaleax

doc/api/console.md

@@ -100,7 +100,7 @@ changes:
     Setting to `true` enables coloring while inspecting values, setting to
     `'auto'` will make color support depend on the value of the `isTTY` property
     and the value returned by `getColorDepth()` on the respective stream.
-    **Default:** `false`
+    **Default:** `'auto'`
 
 Creates a new `Console` with one or two writable stream instances. `stdout` is a
 writable stream to print log or info output. `stderr` is used for warning or

lib/console.js

@@ -67,7 +67,7 @@ function Console(options /* or: stdout, stderr, ignoreErrors = true */) {
       stdout,
       stderr = stdout,
       ignoreErrors = true,
-      colorMode = false
+      colorMode = 'auto'
     } = options);
   } else {
     return new Console({

test/pseudo-tty/console_colors.js

@@ -0,0 +1,9 @@
+'use strict';
+require('../common');
+// Make this test OS-independent by overriding stdio getColorDepth().
+process.stdout.getColorDepth = () => 8;
+process.stderr.getColorDepth = () => 8;
+
+console.log({ foo: 'bar' });
+console.log('%s q', 'string');
+console.log('%o with object format param', { foo: 'bar' });

test/pseudo-tty/console_colors.out

@@ -0,0 +1,3 @@
+{ foo: *[32m'bar'*[39m }
+string q
+{ foo: *[32m'bar'*[39m } with object format param