1519100 - Implement the Top-level await proposal

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P3)

Description

[Alexandre Folle de Menezes]

The proposal is currently in Stage 2.

Comment 1

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

See also the integration in HTML (https://github.com/whatwg/html/pull/4352) and Service Workers (https://github.com/w3c/ServiceWorker/issues/1407).

Comment 2

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Implement basic stencil changes for top-level await; r=arai

Comment 3

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Mark modules as async if we find a top level await while parsinng

This still needs to be cleaned up

Comment 4

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Create AsyncEmitter to handle shared async behavior between functions and modules; r=arai

This change introduces an async emitter that can be shared by FunctionEmitter and module code.

Comment 5

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Implement Top-level async bytecode; r=arai

Depends on D93487

Comment 6

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Add capability in GeneratorObject for modules to be suspended; r=tcampbell,arai,mgaudet

Introduces modules that can be suspended.

Comment 7

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Implement Top-level await specification; r=jonco

Depends on D93523

Comment 8

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Add tests for top level await; r=jonco

Depends on D93524

Comment 9

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Mark modules as async if we find a top level await while parsing; r=jorendorff

Depends on D83773

Comment 10

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Introduce SuspendableContext for async/generators in functions and modules; r=arai,mgaudet

Comment 11

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Move HandlerFunction from streams into the builtin dir; r=mgaudet

Depends on D93524

Comment 12

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Update Dynamic Import to use module promises, and implement module changes in shell.

Depends on D95883

Comment 13

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Implement module promises in html

Depends on D95884

Comment 14

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Move Top-level await functionality behind a flag; r=mgaudet

Depends on D93530

Comment 15

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Update web-platform tests, add expected behavior tests; r=emilio

Depends on D93530

Comment 16

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Adjust jit tests to work with module promises; r=mgaudet

Depends on D96066

Comment 17

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Add flag for experimental Top Level Await feature; r=mgaudet

Comment 18

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Use pref and duplicated old code path to completely pref-off top-level await in the browser; r=emilio,jonco

Depends on D95885

Comment 19

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Add tests for top level await; r=jonco

Add tests behind the TLA flag;

Depends on D97181

Comment 20

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Use pref to completely pref-off top-level await in the browser; r=emilio,jonco

Depends on D95885

Comment 21

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Add tests for top level await; r=jonco

Add tests behind the TLA flag;

Depends on D97184

Comment 22

[Yulia Startsev [:yulia] | Back in Oct.]

Attachment: Bug 1519100 - Use pref and duplicated old code path to completely pref-off top-level await in the browser; r=emilio,jonco

Comment 23

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/da24af409d92
Add flag for experimental Top Level Await feature; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/c723f6b16b67
Move HandlerFunction from streams into the builtin dir; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/d99f0109da7a
Introduce SuspendableContext for async/generators in functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/880873b815a4
Create AsyncEmitter to handle shared async behavior between functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/10194540aff0
Add capability in GeneratorObject for modules to be suspended; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/d7f3440addc7
Implement basic stencil changes for top-level await; r=arai
https://hg.mozilla.org/integration/autoland/rev/5f90543431cb
Mark modules as async if we find a top level await while parsing; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/e0250e4cba61
Implement Top-level async bytecode; r=arai
https://hg.mozilla.org/integration/autoland/rev/90b61247d071
Implement Top-level await specification; r=jonco
https://hg.mozilla.org/integration/autoland/rev/c9afefd66eb7
Update Dynamic Import to use module promises, and implement module changes in shell. r=jonco
https://hg.mozilla.org/integration/autoland/rev/bfd96f55a3bd
Update web-platform tests, add expected behavior tests; r=emilio
https://hg.mozilla.org/integration/autoland/rev/47cf4bde107e
Implement module promises in html r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/ee02050e3c97
Use pref to completely pref-off top-level await in the browser; r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/5b89081f0f08
Add tests for top level await; r=jonco
https://hg.mozilla.org/integration/autoland/rev/7302ebdbaa35
Adjust jit tests to work with module promises; r=mgaudet

Comment 24

[Bogdan Tara[:bogdan_tara | bogdant]]

Backed out 15 changesets (bug 1519100) for wpt leaks.

Push with failure: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&searchStr=windows%2C10%2Cx64%2Cdebug%2Cweb%2Cplatform%2Ctests%2Ctest-windows10-64%2Fdebug-web-platform-tests-e10s%2Cwpt3&fromchange=c8f03513e3a59cdf47f1b81ad911a84eae9b2ff9&tochange=cc51b2d4ae85fa2bcdc0f184d0436e806a7bcbbd&selectedTaskRun=SZJVtRk4Q_GsewEczGU5Dg.0

Backout link: https://hg.mozilla.org/integration/autoland/rev/3c3198bf2d4a541679012a100af53228a9c608d7

Failure log: https://treeherder.mozilla.org/logviewer?job_id=323343568&repo=autoland&lineNumber=21759

Comment 25

[Nick Alexander :nalexander [he/him]]

Yulia: hooray for top-level await! I'm curious: will xpcshell have top-level await? I've actually wanted that in the very recent past.

Comment 26

[Yulia Startsev [:yulia] | Back in Oct.]

Hi Nick:

So.. from my understanding xpcshell currently only compiles to global scripts. Top-Level await is restricted to modules. These are two different parse goals, so for now Top-Level await won't work for xpcshell, at least to my knowledge.

It should be possible to enable it, but I would need to talk to someone who knows more about xpcshell. You can use it in the js-shell with the flag --enable-top-level-await and -m for a module goal.

Comment 27

[Nick Alexander :nalexander [he/him]]

(In reply to Yulia Startsev from comment #26)

Hi Nick:

So.. from my understanding xpcshell currently only compiles to global scripts. Top-Level await is restricted to modules. These are two different parse goals, so for now Top-Level await won't work for xpcshell, at least to my knowledge.

Fascinating, TIL. Thanks, Yulia!

Comment 28

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a3ea6c49dbf7
Add flag for experimental Top Level Await feature; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/98146209da6f
Move HandlerFunction from streams into the builtin dir; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/9f559a616909
Introduce SuspendableContext for async/generators in functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/b521ccd694f8
Create AsyncEmitter to handle shared async behavior between functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/bab7e81a6c2c
Add capability in GeneratorObject for modules to be suspended; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/d5bff6c95feb
Implement basic stencil changes for top-level await; r=arai
https://hg.mozilla.org/integration/autoland/rev/3a0a021acc08
Mark modules as async if we find a top level await while parsing; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/8b5244786634
Implement Top-level async bytecode; r=arai
https://hg.mozilla.org/integration/autoland/rev/63d506024693
Implement Top-level await specification; r=jonco
https://hg.mozilla.org/integration/autoland/rev/683743bd0395
Update Dynamic Import to use module promises, and implement module changes in shell. r=jonco
https://hg.mozilla.org/integration/autoland/rev/55918f941155
Update web-platform tests, add expected behavior tests; r=emilio
https://hg.mozilla.org/integration/autoland/rev/53a792431e11
Implement module promises in html r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/1155eecec034
Use pref to completely pref-off top-level await in the browser; r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/019b00c63941
Add tests for top level await; r=jonco
https://hg.mozilla.org/integration/autoland/rev/16dc37dadf05
Adjust jit tests to work with module promises; r=mgaudet

Comment 29

[Yulia Startsev [:yulia] | Back in Oct.]

eh, nuts that wasn't what I wanted to do... revert incoming..

Comment 30

[Razvan Maries]

Backed out as requested: https://hg.mozilla.org/integration/autoland/rev/ca855dab98dbe9dec01e236125b6ed557fd9637d

Comment 31

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6bdc2b79fa26
Add flag for experimental Top Level Await feature; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/ff6fd518d035
Move HandlerFunction from streams into the builtin dir; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/c11b43616a2f
Introduce SuspendableContext for async/generators in functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/d7f3a9ac1933
Create AsyncEmitter to handle shared async behavior between functions and modules; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/96c7515c8a1b
Add capability in GeneratorObject for modules to be suspended; r=arai,mgaudet
https://hg.mozilla.org/integration/autoland/rev/aa28d891047e
Implement basic stencil changes for top-level await; r=arai
https://hg.mozilla.org/integration/autoland/rev/406c05b73d5b
Mark modules as async if we find a top level await while parsing; r=mgaudet
https://hg.mozilla.org/integration/autoland/rev/18bbeedf4c2e
Implement Top-level async bytecode; r=arai
https://hg.mozilla.org/integration/autoland/rev/740f71543c0e
Implement Top-level await specification; r=jonco
https://hg.mozilla.org/integration/autoland/rev/f9bea80a5393
Update Dynamic Import to use module promises, and implement module changes in shell. r=jonco
https://hg.mozilla.org/integration/autoland/rev/1ffd544310f6
Update web-platform tests, add expected behavior tests; r=emilio
https://hg.mozilla.org/integration/autoland/rev/1f8c2419d053
Implement module promises in html r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/76a1c42b797e
Use pref to completely pref-off top-level await in the browser; r=emilio,jonco
https://hg.mozilla.org/integration/autoland/rev/f3a874302dba
Add tests for top level await; r=jonco
https://hg.mozilla.org/integration/autoland/rev/7d9c82add62d
Adjust jit tests to work with module promises; r=mgaudet

Comment 32

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/6bdc2b79fa26
https://hg.mozilla.org/mozilla-central/rev/ff6fd518d035
https://hg.mozilla.org/mozilla-central/rev/c11b43616a2f
https://hg.mozilla.org/mozilla-central/rev/d7f3a9ac1933
https://hg.mozilla.org/mozilla-central/rev/96c7515c8a1b
https://hg.mozilla.org/mozilla-central/rev/aa28d891047e
https://hg.mozilla.org/mozilla-central/rev/406c05b73d5b
https://hg.mozilla.org/mozilla-central/rev/18bbeedf4c2e
https://hg.mozilla.org/mozilla-central/rev/740f71543c0e
https://hg.mozilla.org/mozilla-central/rev/f9bea80a5393
https://hg.mozilla.org/mozilla-central/rev/1ffd544310f6
https://hg.mozilla.org/mozilla-central/rev/1f8c2419d053
https://hg.mozilla.org/mozilla-central/rev/76a1c42b797e
https://hg.mozilla.org/mozilla-central/rev/f3a874302dba
https://hg.mozilla.org/mozilla-central/rev/7d9c82add62d

Comment 33

[Chris Mills [:cmills]]

Rumyra got this new functionality documented on MDN! See https://github.com/mdn/content/issues/297#issuecomment-762767516 for descriptions of what she did.

Please let us know if you notice anything that needs updating, or can think of anything else you'd like to see added.