1710433 - [META] Symbols as WeakMap property keys

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Yulia Startsev [:yulia]]

Currently at stage 2

Comment 1

[Alexandre Folle de Menezes]

Proposal now in Stage 3

Comment 2

[Xidorn Quan [:xidorn] UTC+10]

I have the following test code:

const map = new WeakMap();
const key = Symbol();
map.set(key, 42);

It throws error:

Uncaught TypeError: WeakMap key Symbol() must be an object or an unregistered symbol

However, it works fine on both Chrome and Safari, which means there can be compatibility issue arises from it, and the behavior here is inconsistent with this error message, which is very confusing.

Comment 3

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi] OOO ~ Feb.7]

(In reply to Xidorn Quan [:xidorn] UTC+11 from comment #2)

However, it works fine on both Chrome and Safari, which means there can be compatibility issue arises from it, and the behavior here is inconsistent with this error message, which is very confusing.

Have you turned on the pref "javascript.options.experimental.symbols_as_weakmap_keys" ?
It is still off by default.

Comment 4

[Xidorn Quan [:xidorn] UTC+10]

(In reply to Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi] from comment #3)

Have you turned on the pref "javascript.options.experimental.symbols_as_weakmap_keys" ?
It is still off by default.

No. Should there be a bug tracking this pref change? Also should we have the error thrown adapt to the availability of this feature, and potentially even mention the tracking bug?

Comment 6

[andseier]

Any updates on this one? I wanted to start using Symbols as WeakMap keys, but I just noticed that it breaks in FF when I test. Thanks!

Comment 7

[csvn.dev]

I think when using "lib": ["es2023"] with Typescript, the es2023.collection is only unsupported in Firefox now. It would be great if this last "ES2023" feature was supported in Firefox as well.

Comment 8

[Will Medina [:willyelm]]

Hi Tom

Since we keep meta bugs open to track future spec changes and issues, should we move the webcompat webcompat:risk-moderate whiteboard tag to Bug 1863140?

Comment 9

[Thomas Wisniewski [:twisniewski]]

Yes, definitely. I was intending to revisit meta-bugs which I've marked with risk scores ASAP, to move the scores as appropriate to their sub-bugs. I'll move this one as you suggested now (and mark that bug as parity-chrome and -safari, since that seems to be the case).