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Test export * as x from and import * as x; export { x } binding equivalence#4606

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nicolo-ribaudo:ambiguous-binding
Nov 26, 2025
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Test export * as x from and import * as x; export { x } binding equivalence#4606
Ms2ger merged 2 commits intotc39:mainfrom
nicolo-ribaudo:ambiguous-binding

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@nicolo-ribaudo nicolo-ribaudo commented Oct 28, 2025 •
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This PR adds tests for tc39/ecma262#3715.

The first commit just moves the tests related to binding ambiguity to a single folder, so that it's easier to tell what is already tested.

@nicolo-ribaudo nicolo-ribaudo force-pushed the ambiguous-binding branch 7 times, most recently from 0ae13c9 to ae7fc83 Compare October 28, 2025 10:39
@nicolo-ribaudo nicolo-ribaudo marked this pull request as ready for review October 28, 2025 10:41
@nicolo-ribaudo nicolo-ribaudo requested a review from a team as a code owner October 28, 2025 10:41
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nicolo-ribaudo commented Oct 28, 2025

SM/JSC pass all the tests, while V8/engine262/XS fail test/language/module-code/ambiguous-export-bindings/namespace-unambiguous-if-export-start-as-from.js

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nicolo-ribaudo commented Oct 28, 2025

Marking as draft because I plan to present something related to this in plenary.

@nicolo-ribaudo nicolo-ribaudo marked this pull request as draft October 28, 2025 10:45
@ptomato ptomato added the awaiting consensus This needs committee consensus before it can be eligible to be merged. label Oct 29, 2025
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guybedford commented Oct 30, 2025 •
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Hmm, what is the value in allowing export * as foo to not be an ambiguous error? Is it not just an oversight that this doesn't throw as an ambiguous case? It doesn't seem to match the expectations for other unambiguous cases to me.

@guybedford guybedford mentioned this pull request Nov 6, 2025
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bakkot commented Nov 24, 2025 •
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I believe the behavior here has consensus (looks like it's asserting the post-tc39/ecma262#3715 behavior). @nicolo-ribaudo did you want to do any further updates or is this ready to review?

@ptomato ptomato added has consensus This has committee consensus and removed awaiting consensus This needs committee consensus before it can be eligible to be merged. labels Nov 24, 2025
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nicolo-ribaudo commented Nov 25, 2025

The PR is testing the old behavior

@nicolo-ribaudo nicolo-ribaudo marked this pull request as ready for review November 25, 2025 09:09
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nicolo-ribaudo commented Nov 25, 2025

Updated ✔️

@nicolo-ribaudo nicolo-ribaudo changed the title Add test for difference between export * as x from and import * as x; export { x } Test export * as x from and import * as x; export { x } binding equivalence Nov 25, 2025
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nicolo-ribaudo commented Nov 25, 2025
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...xport-bindings/namespace-unambiguous-if-export-star-as-from-and-import-star-as-and-export.js Outdated
export * from "./namespace-export-star-as-from-1_FIXTURE.js";
export * from "./namespace-import-star-as-and-export-1_FIXTURE.js";

import { foo } from './namespace-ambiguous-if-import-star-as-and-export.js';
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Before the spec change, this would be an error.

.../module-code/ambiguous-export-bindings/namespace-unambiguous-if-import-star-as-and-export.js Outdated
export * from "./namespace-import-star-as-and-export-1_FIXTURE.js";
export * from "./namespace-import-star-as-and-export-2_FIXTURE.js";

import { foo } from './namespace-ambiguous-if-import-star-as-and-export.js';
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Before the spec change, this would be an error.

@nicolo-ribaudo nicolo-ribaudo force-pushed the ambiguous-binding branch 2 times, most recently from 6cdfc0e to b47cae6 Compare November 25, 2025 15:20
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Oh, I overlooked the negative bits earlier, oops.

Anyway, this looks good to me other than the descriptions I commented on. Specifically, it is testing

  • that import { foo } from 'bar'; export { foo } does not conflict with export { foo } from 'bar' (in import-and-export-propagates-binding.js) - not technically part of the changes in the PR, but good to test
  • that two import * as foo from 'bar'; export { foo } do not conflict with each other (in namespace-unambiguous-if-import-star-as-and-export.js)
  • that two export * as foo from 'bar' do not conflict with each other (in the namespace-unambiguous-if-export-star-as-from.js test)
  • that export * as foo from 'bar' does not conflict with import * as foo from 'bar'; export { foo } (in namespace-unambiguous-if-export-star-as-from-and-import-star-as-and-export.js)

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Thanks

@Ms2ger Ms2ger enabled auto-merge (rebase) November 26, 2025 10:30
@Ms2ger Ms2ger merged commit 0718086 into tc39:main Nov 26, 2025
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@nicolo-ribaudo nicolo-ribaudo deleted the ambiguous-binding branch November 26, 2025 14:22
lando-prod-mozilla bot pushed a commit to mozilla-firefox/firefox that referenced this pull request Nov 26, 2025
@nicolo-ribaudo @jonco3
Bug 2002191 - Align indirect and direct module namespace re-exports r…
61644fd 
…=jonco

This patch implements tc39/ecma262#3715, to make

  import * as ns from "mod";
  export { ns };

behave the same as

  export * as ns from "mod";

Tested by tc39/test262#4606

Differential Revision: https://phabricator.services.mozilla.com/D274013
@nicolo-ribaudo nicolo-ribaudo mentioned this pull request Nov 26, 2025
Merged
gecko-dev-updater pushed a commit to marco-c/gecko-dev-wordified-and-comments-removed that referenced this pull request Nov 27, 2025
@marco-c
Bug 2002191 - Align indirect and direct module namespace re-exports r…
effd9e9 
…=jonco

This patch implements tc39/ecma262#3715, to make

  import * as ns from "mod";
  export { ns };

behave the same as

  export * as ns from "mod";

Tested by tc39/test262#4606

Differential Revision: https://phabricator.services.mozilla.com/D274013

UltraBlame original commit: d14a908552e6d040c7538351430b3152a4a36887
gecko-dev-updater pushed a commit to marco-c/gecko-dev-comments-removed that referenced this pull request Nov 27, 2025
@marco-c
Bug 2002191 - Align indirect and direct module namespace re-exports r…
136985b 
…=jonco

This patch implements tc39/ecma262#3715, to make

  import * as ns from "mod";
  export { ns };

behave the same as

  export * as ns from "mod";

Tested by tc39/test262#4606

Differential Revision: https://phabricator.services.mozilla.com/D274013

UltraBlame original commit: d14a908552e6d040c7538351430b3152a4a36887
gecko-dev-updater pushed a commit to marco-c/gecko-dev-wordified that referenced this pull request Nov 27, 2025
@marco-c
Bug 2002191 - Align indirect and direct module namespace re-exports r…
d859cc0 
…=jonco

This patch implements tc39/ecma262#3715, to make

  import * as ns from "mod";
  export { ns };

behave the same as

  export * as ns from "mod";

Tested by tc39/test262#4606

Differential Revision: https://phabricator.services.mozilla.com/D274013

UltraBlame original commit: d14a908552e6d040c7538351430b3152a4a36887
webkit-commit-queue pushed a commit to nicolo-ribaudo/WebKit that referenced this pull request Dec 5, 2025
@nicolo-ribaudo @sosukesuzuki
Align import * as ns; export { ns } with export * as ns
a2cac8e 
https://bugs.webkit.org/show_bug.cgi?id=303141

Reviewed by Yusuke Suzuki and Sosuke Suzuki.

This patch changes JSC's handling of `import * as ns; export { ns }`
to align with tc39/ecma262#3715, which reached
consensus in the Nov 2025 TC39 meeting.

This will be tested by tc39/test262#4606, for
now I manually verified that the relevant tests in that PR are failing
before this patch and passing after it.

* Source/JavaScriptCore/parser/ModuleAnalyzer.cpp:
(JSC::ModuleAnalyzer::exportVariable):

Canonical link: https://commits.webkit.org/303952@main
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