buffer: show hidden item count

This adds the number of hidden items in case INSPECT_MAX_BYTES is
exceeded.

PR-URL: #22289
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/buffer.js

@@ -683,8 +683,9 @@ Buffer.prototype[customInspectSymbol] = function inspect() {
   var str = '';
   var max = exports.INSPECT_MAX_BYTES;
   str = this.toString('hex', 0, max).replace(/(.{2})/g, '$1 ').trim();
-  if (this.length > max)
-    str += ' ... ';
+  const remaining = this.length - max;
+  if (remaining > 0)
+    str += ` ... ${remaining} more byte${remaining > 1 ? 's' : ''}`;
   return `<${this.constructor.name} ${str}>`;
 };
 Buffer.prototype.inspect = Buffer.prototype[customInspectSymbol];

test/parallel/test-buffer-inspect.js

@@ -33,7 +33,7 @@ b.fill('1234');
 let s = buffer.SlowBuffer(4);
 s.fill('1234');
 
-let expected = '<Buffer 31 32 ... >';
+let expected = '<Buffer 31 32 ... 2 more bytes>';
 
 assert.strictEqual(util.inspect(b), expected);
 assert.strictEqual(util.inspect(s), expected);

test/parallel/test-buffer-prototype-inspect.js

@@ -19,5 +19,5 @@ const util = require('util');
 
 {
   const buf = Buffer.from('x'.repeat(51));
-  assert.ok(/^<Buffer (?:78 ){50}\.\.\. >$/.test(util.inspect(buf)));
+  assert.ok(/^<Buffer (?:78 ){50}\.\.\. 1 more byte>$/.test(util.inspect(buf)));
 }