class name not being inherited in an anonymous class since 12.16.0

[YoannMa]

• Version: v12.16.0
• Platform: Linux yoann-MS-7C09 4.15.0-74-generic # 84-Ubuntu SMP Thu Dec 19 08:06:28 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem:

What steps will reproduce the bug?

Running this script on v12.16.0 will return false when before it was returning true

'use strict';

const extend = (Model) => class extends Model {}

class FOO {};

const BAR = extend(FOO);

console.log(BAR.name === 'FOO');

How often does it reproduce? Is there a required condition?

Always since v12.16.0

What is the expected behavior?

I do not know which one is the expected behavior.

What do you see instead?

• v12.15.0 : true
• v12.16.0 : false
• v13.8.0 : false

Additional information

[vdeturckheim]

With jsvu I managed to find this on v8. It seems it appeared between v8-7.8.185 and v8-7.8.186.

I am not sure if this is a bug fixed there.

[targos]

Could you check what spidermonkey and jsc do?

[vdeturckheim]

Sure, good point:

• sm-latest: BAR.name !== 'FOO'
• jsc-latest: BAR.name !== 'FOO'

This looks indeed like a bugfix in v8 (or at least an alignment on other engines)

[bnoordhuis]

This is indeed a spec conformance thing: the .name property of an anonymous class should be the empty string. A more minimal test case is this:

// should be '', is 'Object' with older node versions
(class extends Object {}).name

The V8 change that's responsible was reverted because of fuzzer issues and hasn't been relanded, AFAICT.

We should probably close this because it's ultimately not a Node.js issue but cc @nodejs/v8 just in case.

[vdeturckheim]

Thanks for the clarification @bnoordhuis !