util: add boxed BigInt formatting to util.inspect

Before:

> Object(7n)
BigInt {}

After:

> Object(7n)
[BigInt: 7n]

PR-URL: #19341
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>

lib/util.js

@@ -580,6 +580,13 @@ function formatValue(ctx, value, recurseTimes, ln) {
         if (keyLength === 0)
           return ctx.stylize(`[Boolean: ${formatted}]`, 'boolean');
         base = `[Boolean: ${formatted}]`;
+        // eslint-disable-next-line valid-typeof
+      } else if (typeof raw === 'bigint') {
+        // Make boxed primitive BigInts look like such
+        const formatted = formatPrimitive(stylizeNoColor, raw);
+        if (keyLength === 0)
+          return ctx.stylize(`[BigInt: ${formatted}]`, 'bigint');
+        base = `[BigInt: ${formatted}]`;
       } else if (typeof raw === 'symbol') {
         const formatted = formatPrimitive(stylizeNoColor, raw);
         return ctx.stylize(`[Symbol: ${formatted}]`, 'symbol');

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

@@ -8,3 +8,5 @@ const assert = require('assert');
 const { inspect } = require('util');
 
 assert.strictEqual(inspect(1n), '1n');
+assert.strictEqual(inspect(Object(-1n)), '[BigInt: -1n]');
+assert.strictEqual(inspect(Object(13n)), '[BigInt: 13n]');