Inspected objects’ symbol key properties are hidden by default

[mightyiam]

• Version: v7.1.0
• Platform: Linux shahar-desktop 4.8.0-27-generic docs: added a the #29-Ubuntu SMP Thu Oct 20 21:03:13 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: ?

I find it useful to be able to inspect the contents of an object by by looking at it in an interactive session. I'll call this the "debug representation". What is the correct term, please?

Now that we have symbols I'm experimenting with using them as object keys. I think it should reduce chance of accidental name collisions/overwrites, if done properly.

Thing is—while inspection of objects with "normal" keys is easy:

{ foo: undefined }
// { foo: undefined }

Inspection of objects with symbol keys is hard:

let obj = { [Symbol()]: undefined }

obj
// {}

While, obviously:

Object.getOwnPropertySymbols(obj)
// [ Symbol() ]

😢

I expect this:

obj
// { Symbol(): undefined }

It makes sense, doesn't it?

We already have this, so it makes sense to expect what I'm expecting, does’t it?

Symbol()
// Symbol()
Symbol('foo')
// Symbol(foo)

Chrome DevTools seems to do the right thing:

[vkurchatkin]

You can enable this behaviour like this:

util.inspect.defaultOptions.showHidden = true

[mightyiam]

That's great advice, @vkurchatkin. Thank you.

Is there a reason why this is not default, please? This issue was closed without providing a reason.

[addaleax]

@mightyiam Fyi, the docs about this are in https://nodejs.org/api/util.html#util_util_inspect_object_options

Generally util.inspect uses Object.keys() to determine which keys are to be displayed; if you think Symbols should be displayed by default, too, you can open a pull request to change it. But I wouldn’t be surprised if people have come to rely on the current behaviour or even just like it.

[bnoordhuis]

I somewhat agree that the current behavior is a little inconsistent: you use showHidden to include non-enumerable properties but symbol properties are normally enumerable so why do you need showHidden=true to make them show up?

[vkurchatkin]

symbol properties are normally enumerable

Not really, you need getOwnPropertySymbols for symbols the same way you need getOwnPropertyNames for non-enumerable properties

[bnoordhuis]

Yes, but then again, no. What I mean is this:

$ node
> var o = {}, k = Symbol(); o[k] = 42
42

> Object.getOwnPropertyDescriptor(o, k)
{ value: 42,
  writable: true,
  enumerable: true,
  configurable: true }

[vkurchatkin]

@bnoordhuis well, that's how it is in the spec, right? enumerable is true, but they are not in fact enumerable

[mightyiam]

Yet, this is not about the spec, enumerability or anything like that. This is about our ability and ease when debugging is how I see it. Do you use symbol keys? If so, don't you find it unreasonable that they're not showing up in the interactive mode? I do. I find it awful. I'll make a PR if it isn't too hard.