Node: Feature request: backport node patch for `Array#values`

[ljharb]

The Array#values function was temporarily removed from v8 because it broke web compatibility.

node/io.js, however, do not have that concern.

Per https://github.com/joyent/node/issues/25324#issuecomment-104806702, if io.js merges in these two commits, io.js (and future versions of node) will retain Array.prototype.values rather than being hindered by web compat concerns.

Can this be brought in to the next non-patch release of io.js?

[bnoordhuis]

We have a policy of only carrying patches that have been accepted upstream. Here, it's been reverted upstream and it's unclear when it's going to get added back.

Minor aside, array.values() is identical to array[Symbol.iterator]() and that still works in V8. They're literally the same function.

[ljharb]

:-/ how will node's policy of having this patch, and io.js's policy of not allowing it, work together in the upcoming merge?

Yes, you're correct - by spec, they're === to each other. However, that doesn't change the fact that having .values makes arrays in line with Map and Set (also the weak varieties), and also is a clearer semantic for some than referencing Symbol.iterator.

[Fishrock123]

Uh oh, not good.

The node patch should have floated a version that warned about being deprecated.

[Fishrock123]

Ok I just checked, and it's in the spec for es6, so it will eventually land. When? That's up to v8. :S

[ljharb]

Yes, exactly - this function is required by the spec, and v8 is only holding it back for web compat. I'd say that v8 should keep it in and Chrome should remove it, but they didn't do it that way for whatever reason.

[Fishrock123]

I'd say that v8 should keep it in and Chrome should remove it, but they didn't do it that way for whatever reason.

Wasn't the 0.12 v8 version using some sort of wrong (non-v8-release-line) v8 version?

If so, that's kinda the problem. :(

[trevnorris]

@Fishrock123 It was, but has been fixed.

[Fishrock123]

It was, but has been fixed.

Right but there were still releases in the wild with this Array feature in from them being dev versions. :/ (In the past now, but I suspect this will just be a general ouch until v8 adds it again.)

[Slayer95]

ES6 hasn't been approved yet afaik. Given that Array#values breaks web-compatibility, it wouldn't be harebrained to think that it may get rejected in this month's meeting.

[ljharb]

@Slayer95 Yes, it most certainly has been, and is finalized - as of last week's (May) TC39 meeting. Array#values is definitely in ES6.

[rlidwka]

:-/ how will node's policy of having this patch, and io.js's policy of not allowing it, work together in the upcoming merge?

I would expect to see that patch in node 0.12 branch for b/w compatibility reasons, but io.js (and future converged repo) should wait until v8 re-adds it.

[domenic]

-1, should not add features that are not agreed to be added by V8 (and SpiderMonkey). It may be in the ES2015 spec but that doesn't mean it'll be part of the actual JavaScript language accepted and implemented by engines.

[Fishrock123]

I think I'm going to close this for now. I would consider it a bug that it even existed unflagged in node (without being stable yet).

[ChALkeR]

This should be mentioned in the changelog of the converged release, I think.
Among with other breaking changes from 0.12.

[Fishrock123]

Will do.

[gsathya]

I re enabled Array.prototype.values in Chrome 66 with an embedder flag. We'll know if it's web compatible or not once Chrome 66 becomes stable.

cc @MylesBorins

[MylesBorins]

Reopening this issue to track. We should likely enable it in 10.x assuming it doesn't get reverted again. @gsathya does it make sense for us to enable it a couple weeks later or perhaps inherit it in the 6.7 upgrade?

[gsathya]

I think waiting for 6.7 is a good idea. I'll enable it by default in V8 6.8 and backport it to V8 6.7 (since 6.7 is branching right now)

[targos]

Friendly ping. It looks it's still behind a flag in 6.8?

[gsathya]

Thanks @targos. We're still ramping up Chrome 66 release rollout, so I don't have enough data yet to know if it's web compatible.

[Trott]

Seems like Array.prototype.values() is available in Node.js 10.x and 11.x. It's not there in 8.x and 6.x. Is this close-able on the grounds that it's unlikely to be backported to 8.x and 6.x? Or is that precisely the ask here and it's something that's still wanted?

[ljharb]

It should still be backported if possible, imo.

[bnoordhuis]

v6.x is EOL and v8.x is in maintenance mode now. I'd say it's exceedingly unlikely that a back-port will be accepted at this stage because it doesn't meet the criteria:

Once a release moves into Maintenance mode, only critical bugs, critical security fixes [..] will be permitted.

Ergo, I'll go ahead and close this out.

[ljharb]

Certainly dragging our heels on it for 4 or 1 year makes it obsolete, but that doesn’t mean it’s highly subpar that it wasn’t backported. I hope we won’t be so glacial with such things in the future.