util: prevent leaking internal properties

This prevents leaking of the internal `inspect()` properties when
using a custom inspect function.

It also aligns the indentation to the way it was in v8.0.0 since
that changed unintentionally. All strings returned by the custom
inspect function will now be indented appropriately to the current
depth.

PR-URL: https://github.com/nodejs/node/pull/24971
Refs: https://github.com/nodejs/node/issues/24765
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/test/parallel/test-util-inspect.js b/test/parallel/test-util-inspect.js
index 21a0634323..4e9f5ac004 100644
--- a/test/parallel/test-util-inspect.js
+++ b/test/parallel/test-util-inspect.js
@@ -775,9 +775,21 @@ util.inspect({ hasOwnProperty: null });
 
   assert.strictEqual(util.inspect(subject), "{ foo: 'bar' }");
 
-  subject[util.inspect.custom] = (depth, opts) => {
-    assert.strictEqual(opts.customInspectOptions, true);
-  };
+  subject[util.inspect.custom] = common.mustCall((depth, opts) => {
+    const clone = { ...opts };
+    // This might change at some point but for now we keep the stylize function.
+    // The function should either be documented or an alternative should be
+    // implemented.
+    assert.strictEqual(typeof opts.stylize, 'function');
+    assert.strictEqual(opts.seen, undefined);
+    assert.strictEqual(opts.budget, undefined);
+    assert.strictEqual(opts.indentationLvl, undefined);
+    assert.strictEqual(opts.showHidden, false);
+    opts.showHidden = true;
+    return { [util.inspect.custom]: common.mustCall((depth, opts2) => {
+      assert.deepStrictEqual(clone, opts2);
+    }) };
+  });
 
   util.inspect(subject, { customInspectOptions: true });
 
@@ -1593,7 +1605,7 @@ util.inspect(process);
   );
   const longList = util.inspect(list, { depth: Infinity });
   const match = longList.match(/next/g);
-  assert(match.length > 1000 && match.length < 10000);
+  assert(match.length > 500 && match.length < 10000);
   assert(longList.includes('[Object: Inspection interrupted ' +
     'prematurely. Maximum call stack size exceeded.]'));
 }