util: add bigint formatting to util.inspect

PR-URL: #18412
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: devsnek

lib/util.js

@@ -342,6 +342,7 @@ inspect.colors = Object.assign(Object.create(null), {
 inspect.styles = Object.assign(Object.create(null), {
   'special': 'cyan',
   'number': 'yellow',
+  'bigint': 'yellow',
   'boolean': 'yellow',
   'undefined': 'grey',
   'null': 'bold',
@@ -650,6 +651,9 @@ function formatPrimitive(fn, value, ctx) {
   }
   if (typeof value === 'number')
     return formatNumber(fn, value);
+  // eslint-disable-next-line valid-typeof
+  if (typeof value === 'bigint')
+    return fn(`${value}n`, 'bigint');
   if (typeof value === 'boolean')
     return fn(`${value}`, 'boolean');
   if (typeof value === 'undefined')

test/parallel/test-util-inspect-bigint.js

@@ -0,0 +1,10 @@
+'use strict';
+
+// Flags: --harmony-bigint
+
+require('../common');
+const assert = require('assert');
+
+const { inspect } = require('util');
+
+assert.strictEqual(inspect(1n), '1n');