stream: improve buffer list inspection

This makes sure the indentation level is correct, no matter if the
inspected buffer list is inspected on a deeper level and custom
inspect options are now passed through to the actual inspection.

PR-URL: #23109
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/streams/buffer_list.js

@@ -158,8 +158,14 @@ module.exports = class BufferList {
     return ret;
   }
 
-  [inspect.custom]() {
-    const obj = inspect({ length: this.length });
-    return `${this.constructor.name} ${obj}`;
+  // Make sure the linked list only shows the minimal necessary information.
+  [inspect.custom](_, options) {
+    return inspect(this, {
+      ...options,
+      // Only inspect one level.
+      depth: 0,
+      // It should not recurse.
+      customInspect: false
+    });
   }
 };

test/parallel/test-stream2-readable-from-list.js

@@ -25,6 +25,7 @@ require('../common');
 const assert = require('assert');
 const fromList = require('_stream_readable')._fromList;
 const BufferList = require('internal/streams/buffer_list');
+const util = require('util');
 
 function bufferListFromArray(arr) {
   const bl = new BufferList();
@@ -41,6 +42,16 @@ function bufferListFromArray(arr) {
                Buffer.from('kuel') ];
   list = bufferListFromArray(list);
 
+  assert.strictEqual(
+    util.inspect([ list ], { compact: false }),
+    `[
+  BufferList {
+    head: [Object],
+    tail: [Object],
+    length: 4
+  }
+]`);
+
   // read more than the first element.
   let ret = fromList(6, { buffer: list, length: 16 });
   assert.strictEqual(ret.toString(), 'foogba');