feat: implement Iterator.zip and Iterator.zipKeyed (#4564) by yush-1018 · Pull Request #4946 · boa-dev/boa

yush-1018 · 2026-03-08T07:47:40Z

Implements the TC39 Joint Iteration proposal (#4564).

Adds Iterator.zip and Iterator.zipKeyed static methods with support for
"shortest", "longest", and "strict" modes. Includes a new ZipIterator
backing object with proper iterator protocol handling.

github-actions · 2026-03-08T07:58:10Z

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,073	50,073	0
Ignored	2,072	2,072	0
Failed	818	818	0
Panics	0	0	0
Conformance	94.54%	94.54%	0.00%

Tested main commit: 055ee0958ce332f3f99af27536a7c6f9a91def27
Tested PR commit: 455af3a0d140f320fa6877fb11aa665825857998
Compare commits: 055ee09...455af3a

nekevss

Please look at some other built-in for general style on implementation.

Most steps should have some level of documentation. There's a lot of nesting here and it's not clear whether it's a result of the specification or can be improved in another way.

nekevss · 2026-03-08T20:31:08Z

+        let iterables = args.get_or_undefined(0);
+        let options = args.get_or_undefined(1);
+
+        // 1. If iterables is not an Object, throw a TypeError exception.


issue: include the entire specification text.

nekevss · 2026-03-08T20:36:24Z

+        let mode = Self::parse_zip_mode(options, context)?;
+
+        // 6-7. Parse padding option (only for "longest" mode).
+        let padding_option = if mode == ZipMode::Longest {


suggestion: rewrite these using some if-let chains

nekevss · 2026-03-08T20:39:36Z

+        let mode = Self::parse_zip_mode(options, context)?;
+
+        // 6-7. Parse padding option.
+        let padding_option = if mode == ZipMode::Longest {


suggestion: use if-let chains here

nekevss · 2026-03-08T20:40:47Z

+    }
+}
+
+impl IntrinsicObject for ZipIterator {


nit: move this higher up in the file

yush-1018 · 2026-03-10T20:03:58Z

Hey @nekevss,

All review feedback addressed! (Added spec comments, refactored padding parsing with if let, and moved the IntrinsicObject impl).

Ready for review.

Thanks!

jedel1043 · 2026-03-13T06:24:34Z

All the implementation needs to be gated behind the experimental feature, since the proposal hasn't reached stage 4

yush-1018 · 2026-03-18T13:05:41Z

Can you please review this once.

Thanks!

jedel1043 · 2026-03-18T13:39:06Z

Unrelated change

jedel1043 · 2026-03-18T13:39:16Z

Also unrelated

jedel1043 · 2026-03-18T13:39:24Z

Unrelated...

jedel1043 · 2026-03-18T13:42:47Z

Also you didn't address some of Kevin's comments

codecov · 2026-03-18T22:26:26Z

Codecov Report

❌ Patch coverage is 2.94118% with 132 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.42%. Comparing base (6ddc2b4) to head (4e76aa8).
⚠️ Report is 1042 commits behind head on main.

Files with missing lines	Patch %	Lines
...gine/src/builtins/iterable/iterator_constructor.rs	3.60%	107 Missing ⚠️
core/engine/src/builtins/iterable/mod.rs	0.00%	25 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #4946       +/-   ##
===========================================
+ Coverage   47.24%   62.42%   +15.18%     
===========================================
  Files         476      534       +58     
  Lines       46892    59745    +12853     
===========================================
+ Hits        22154    37296    +15142     
+ Misses      24738    22449     -2289

☔ View full report in Codecov by Harness.
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yush-1018 · 2026-03-19T08:14:08Z

PR is ready to review.

Thanks!

nekevss · 2026-03-21T21:35:46Z

Looks like there may be some conflicts that need to be resolved

…nsic

# Conflicts: # core/engine/src/builtins/iterable/tests.rs

yush-1018 · 2026-04-18T12:40:05Z

@jedel1043 ,

Please review the PR.

jedel1043

I see a lot of unnecessary files like cargo_error or check_output. You should remove those.

…n-clean

…psible_match

…ch guard (mutation not allowed in guards)

yush-1018 · 2026-05-12T04:40:40Z

@jedel1043,

can u please review this PR.

yush-1018 · 2026-05-31T19:40:38Z

@nekevss, PR is ready to merge plz take a review.

jedel1043

Had to tweak and refactor a chunk of the implementation to put it closer to the rest of the iterator helpers, but looks good now.

Changes should have been addressed, and I want to merge this asap to fix the bugs

yush-1018 requested a review from a team as a code owner March 8, 2026 07:47

jedel1043 added the C-Builtins PRs and Issues related to builtins/intrinsics label Mar 8, 2026

nekevss previously requested changes Mar 8, 2026

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jedel1043 added A-Enhancement New feature or request Waiting On Author Waiting on PR changes from the author labels Mar 13, 2026

github-actions Bot added the Waiting On Review Waiting on reviews from the maintainers label Mar 17, 2026

yush-1018 marked this pull request as draft March 17, 2026 09:01

yush-1018 force-pushed the feat/joint-iteration-clean branch from 99be867 to cc4de18 Compare March 17, 2026 17:59

github-actions Bot added the C-Tests Issues and PRs related to the tests. label Mar 18, 2026

yush-1018 marked this pull request as ready for review March 18, 2026 13:04

jedel1043 reviewed Mar 18, 2026

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Comment thread core/engine/src/builtins/typed_array/builtin.rs

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Unrelated change

yush-1018 reacted with thumbs up emoji

jedel1043 reviewed Mar 18, 2026

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Comment thread core/engine/src/builtins/typed_array/tests.rs

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Also unrelated

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jedel1043 reviewed Mar 18, 2026

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Comment thread core/engine/src/module/loader/mod.rs

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Unrelated...

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jedel1043 removed the Waiting On Review Waiting on reviews from the maintainers label Mar 18, 2026

yush-1018 force-pushed the feat/joint-iteration-clean branch from 2612098 to 0993de3 Compare March 18, 2026 21:11

yush-1018 added 7 commits March 22, 2026 14:38

feat: implement Iterator.zip and Iterator.zipKeyed (boa-dev#4564)

49dd95a

fix(builtins): address PR feedback for Iterator.zip

03cc3fa

refactor: gate Iterator.zip/zipKeyed behind experimental feature

9f4962f

fix: resolve CI failures by addressing clippy, fmt, and missing intri…

c859d50

…nsic

fix(lint): replace forbidden unwrap usages with expect

4abc0d3

style: run cargo fmt

b317691

fix(lint): use inspect_err instead of map_err

4bb9ae2

yush-1018 added 3 commits April 7, 2026 12:26

Merge upstream main

5c035dc

# Conflicts: # core/engine/src/builtins/iterable/tests.rs

chore: remove accidental scratch files

5a9cd1e

Merge branch 'main' into feat/joint-iteration-clean

d56d5c9

yush-1018 marked this pull request as ready for review April 9, 2026 05:56

jedel1043 requested changes Apr 19, 2026

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yush-1018 added 3 commits April 20, 2026 09:42

chore: remove unnecessary scratch/debug files

d9f5980

Merge remote-tracking branch 'upstream/main' into feat/joint-iteratio…

10336d9

…n-clean

fix(macros): collapse nested if into match guard to fix clippy::colla…

ceee994

…psible_match

yush-1018 marked this pull request as draft April 20, 2026 05:02

yush-1018 added 2 commits April 20, 2026 10:33

fix(macros): use allow attribute for collapsible_match instead of mat…

fde5d02

…ch guard (mutation not allowed in guards)

chore: merge upstream/main and fix clippy collapsible_match

5269d86

yush-1018 marked this pull request as ready for review May 12, 2026 04:40

Merge branch 'main' into feat/joint-iteration-clean

cf5e66d

jedel1043 added 7 commits August 31, 2026 00:34

chore: refactor zip code with spec abstractions

8b4c911

Merge remote-tracking branch 'upstream/main' into joint-iteration-clean

2bd381a

cargo clippy

ba5d0f4

enable tests

34cbe6e

remove superfluous tests

8f4f1de

remove macro change

28b1e47

remove macro change 2

b01d642

jedel1043 approved these changes Aug 31, 2026

View reviewed changes

jedel1043 enabled auto-merge August 31, 2026 06:55

properly close iterators in reverse order

4e76aa8

jedel1043 added this pull request to the merge queue Aug 31, 2026

Merged via the queue into boa-dev:main with commit 10ef235 Aug 31, 2026
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