1496852 - Implement export-ns-from syntax

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P3)

Description

[John-David Dalton]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Steps to reproduce:

Now that export-ns-from has TC39 consensus (https://github.com/tc39/ecma262/pull/1174#issuecomment-425120082) the TC39 is looking for engines to implement.

Comment 1

[Tom S [:evilpie]]

Apparently v8 implemented this behind a flag, and Chakra is in progress. How difficult is this to implement?

Comment 2

[Jon Coppeard (:jonco)]

I suspect it's not too difficult.  Are you interested in working on this?

Comment 3

[Till Schneidereit [:till]]

This was just accepted for merging into the spec, so we should probably up the priority of implementing it.

Comment 4

[Ted Campbell [:tcampbell]]

I'm making an attempt at this as I fix Bug 1614041.

Comment 5

[Ted Campbell [:tcampbell]]

Attachment: Bug 1496852 - Support JavaScript export-ns-from syntax

Add support for export * as ns from "a"; syntax. This was added in
ECMAScript 2020.

One wrinkle in the implementation is that the parser decides whether to use a
lexical vs indirect binding before module linking. Instead, we reserve a
hidden environment slot called "namespace" for each module that can be
referenced by indirect binding maps as needed.

Comment 6

[Ted Campbell [:tcampbell]]

Attachment: Bug 1496852 - Update spec references in Module.js

Update spec references and step numbers to match ES2020. Add TODOs for the
missing steps. There are some editorial changes in latest draft that affect
step numbers, but behaviour is the same for these methods.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6fee4a3c8aa4
Update spec references in Module.js r=jorendorff
https://hg.mozilla.org/integration/autoland/rev/a35461d1fc07
Support JavaScript export-ns-from syntax r=jorendorff

Comment 8

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/6fee4a3c8aa4
https://hg.mozilla.org/mozilla-central/rev/a35461d1fc07

Comment 9

[Florian Scholz (Open Web Docs)]

https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/export#Browser_compatibility
https://wiki.developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/80#JavaScript