console: improve console.group()

Preserve indentation for multiline strings, objects that span multiple
lines, etc.

also make groupIndent non-enumerable

Hide the internal `groupIndent` key a bit by making it non-enumerable
and non-configurable.

PR-URL: https://github.com/nodejs/node/pull/14999
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>

lib/console.js

@@ -60,6 +60,8 @@ function Console(stdout, stderr, ignoreErrors = true) {
   Object.defineProperty(this, '_stderrErrorHandler', prop);
 
   this[kCounts] = new Map();
+
+  Object.defineProperty(this, kGroupIndent, { writable: true });
   this[kGroupIndent] = '';
 
   // bind the prototype functions to this Console instance
@@ -86,7 +88,15 @@ function createWriteErrorHandler(stream) {
   };
 }
 
-function write(ignoreErrors, stream, string, errorhandler) {
+function write(ignoreErrors, stream, string, errorhandler, groupIndent) {
+  if (groupIndent.length !== 0) {
+    if (string.indexOf('\n') !== -1) {
+      string = string.replace(/\n/g, `\n${groupIndent}`);
+    }
+    string = groupIndent + string;
+  }
+  string += '\n';
+
   if (!ignoreErrors) return stream.write(string);
 
   // There may be an error occurring synchronously (e.g. for files or TTYs
@@ -115,8 +125,9 @@ function write(ignoreErrors, stream, string, errorhandler) {
 Console.prototype.log = function log(...args) {
   write(this._ignoreErrors,
         this._stdout,
-        `${this[kGroupIndent]}${util.format.apply(null, args)}\n`,
-        this._stdoutErrorHandler);
+        util.format.apply(null, args),
+        this._stdoutErrorHandler,
+        this[kGroupIndent]);
 };
 
 
@@ -126,8 +137,9 @@ Console.prototype.info = Console.prototype.log;
 Console.prototype.warn = function warn(...args) {
   write(this._ignoreErrors,
         this._stderr,
-        `${this[kGroupIndent]}${util.format.apply(null, args)}\n`,
-        this._stderrErrorHandler);
+        util.format.apply(null, args),
+        this._stderrErrorHandler,
+        this[kGroupIndent]);
 };
 
 
@@ -138,8 +150,9 @@ Console.prototype.dir = function dir(object, options) {
   options = Object.assign({ customInspect: false }, options);
   write(this._ignoreErrors,
         this._stdout,
-        `${this[kGroupIndent]}${util.inspect(object, options)}\n`,
-        this._stdoutErrorHandler);
+        util.inspect(object, options),
+        this._stdoutErrorHandler,
+        this[kGroupIndent]);
 };