2065611 - Implement export star default proposal

Status: RESOLVED FIXED

(Core :: JavaScript: Standard Library, enhancement, P3)

Description

[Dan Minor [:dminor]]

We've had a request to prototype this, even though it's only at Stage 1.

Comment 1

[Nicolò Ribaudo]

Hi, I'm the champion of the proposal :) The spec text is at https://tc39.es/proposal-export-star-default/.

This was presented a few TC39 meetings ago, and there was strong enough support that I plan to propose it for Stage 2.7 soon. While the semantics of the change have a significant level of agreement, the main risk is around web compatibility.

I recently added an (approximate) UseCounter for this to V8, but I'm hoping to also have a flagged implementation in Firefox so that I can get a group of people to try it out and see if anybody finds a website that happens to break.

Comment 2

[Cornelius | CE student]

Attachment: Bug 2065611 - Part 1: Add pref and shell option for Export star default proposal. r=arai,allstarschh

Comment 3

[Cornelius | CE student]

Attachment: Bug 2065611 - Part 2: Implement Export star default proposal behind pref. r=arai,allstarschh

Right now export * from "mod" skips mod's default export; the spec
blocks it. This patch lets it through when the pref is on, by skipping the
"default" checks in GetExportedNames and ResolveExport so default is
treated like any other exported name (ambiguity checks included).

With the Pref off: There's no change in behavior.

I've also added jit-tests covering the basic case, missing default, ambiguous
default, and explicit re-export resolving the ambiguity.

Comment 4

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi]]

Hi, Cornelius
Thanks for taking this bug.
I notice Nicolo has assigned this bug, next time if you want to take a bug with someone assigned,
you can ask if you can take over the bug.
We don't want to spend time doing on the same things.

Comment 5

[Cornelius | CE student]

Hey Yoshi,

I'm working with Nic at Igalia. He's my mentor. He assigned himself so no one can take it before I get to it.

Comment 6

[Yoshi Cheng-Hao Huang [:allstars.chh][:allstarschh][:yoshi]]

(In reply to Cornelius | CE student from comment #5)

I'm working with Nic at Igalia. He's my mentor. He assigned himself so no one can take it before I get to it.

Then you can just assign yourself to this bug.

Comment 7

[Cornelius | CE student]

I can't edit the bug and he's on leave.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/a58cff11691d
https://hg.mozilla.org/integration/autoland/rev/c4923eae3af2
Part 1: Add pref and shell option for Export star default proposal. r=arai,allstarschh
https://github.com/mozilla-firefox/firefox/commit/9cbb8d10c69a
https://hg.mozilla.org/integration/autoland/rev/40da41d07eb4
Part 2: Implement Export star default proposal behind pref. r=arai,allstarschh

Comment 9

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/c4923eae3af2
https://hg.mozilla.org/mozilla-central/rev/40da41d07eb4

Comment 10

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/c4923eae3af2
https://hg.mozilla.org/mozilla-central/rev/40da41d07eb4

Comment 11

[Hamish Willee]

FF157 MDN work for this can be tracked in https://github.com/mdn/content/issues/45699