refactor: noop effect hooks on main thread by HuJean · Pull Request #2424 · lynx-family/lynx-stack

HuJean · 2026-04-03T10:49:17Z

Summary by CodeRabbit

Refactor
- React runtime hooks (useEffect, useLayoutEffect and useImperativeHandle) now become no-ops when running in background contexts, reducing unnecessary work and improving background performance and stability.
Chore
- Patch release prepared to ship the runtime behavior change and supporting internal adjustments.

Checklist

Tests updated (or not required).
Documentation updated (or not required).
Changeset added, and when a BREAKING CHANGE occurs, it needs to be clearly marked (or not required).

changeset-bot · 2026-04-03T10:49:22Z

🦋 Changeset detected

Latest commit: ebe224d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@lynx-js/react	Patch
@lynx-js/react-umd	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

coderabbitai · 2026-04-03T10:49:32Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: c3231be1-f480-45c3-81a0-2167594db387

📥 Commits

Reviewing files that changed from the base of the PR and between c93abfe and f922cca.

📒 Files selected for processing (3)

.changeset/neat-pumas-thank.md
packages/react/runtime/src/hooks/react.ts
packages/react/runtime/src/utils.ts

✅ Files skipped from review due to trivial changes (1)

.changeset/neat-pumas-thank.md

🚧 Files skipped from review as they are similar to previous changes (2)

packages/react/runtime/src/utils.ts
packages/react/runtime/src/hooks/react.ts

📝 Walkthrough

Walkthrough

Added a Changeset and a shared noop utility; useEffect, useLayoutEffect, and useImperativeHandle now act as no-ops when __BACKGROUND__ is truthy, otherwise they delegate to profiling wrappers or Preact implementations as before.

Changes

Cohort / File(s)	Summary
Changeset Documentation `\.changeset/neat-pumas-thank.md`	New changeset added to publish a patch for `@lynx-js/react` recording the hooks refactor.
Hook Implementations `packages/react/runtime/src/hooks/react.ts`	`useEffect` and `useLayoutEffect` now return `noop` when `__BACKGROUND__` is truthy; `useImperativeHandle` is exported from this module and similarly becomes `noop` under `__BACKGROUND__`; otherwise existing profiling vs non-profiling selection remains.
Utility Exports `packages/react/runtime/src/utils.ts`	Added `export const noop: (...args: unknown[]) => unknown = () => {}` as a shared no-op utility.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers

Yradex
hzy

Poem

🐇 I hop through lines where functions sleep,
A tiny noop makes silence deep,
Background whispers call the tune,
Hooks rest softly by the moon,
Hooray — a gentle change for soon!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly and concisely summarizes the main change: making effect hooks (useEffect, useLayoutEffect, useImperativeHandle) into no-ops when running on the main thread, which is the primary objective reflected across all modified files.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch fix/main-thread-effect-hooks-noop

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codecov · 2026-04-03T10:52:02Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@packages/react/runtime/src/hooks/react.ts`:
- Line 163: The ternary for useImperativeHandle is inverted: change the
expression so useImperativeHandle is a no-op on the main thread (when
__BACKGROUND__ is false) like useEffect/useLayoutEffect; specifically update the
assignment involving useImperativeHandle, usePreactUseImperativeHandle, noop and
__BACKGROUND__ so the noop branch runs when __BACKGROUND__ is false and the real
implementation (usePreactUseImperativeHandle) runs when __BACKGROUND__ is true.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 2efedd07-81ae-430c-9384-6d5e4dec4e96

📥 Commits

Reviewing files that changed from the base of the PR and between 7782a4c and 68e40d1.

📒 Files selected for processing (3)

.changeset/neat-pumas-thank.md
packages/react/runtime/src/hooks/react.ts
packages/react/runtime/src/utils.ts

packages/react/runtime/src/hooks/react.ts

codspeed-hq · 2026-04-03T11:07:36Z

Merging this PR will degrade performance by 14.74%

❌ 1 regressed benchmark
✅ 71 untouched benchmarks
⏩ 21 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
❌	`transform 1000 view elements`	40.3 ms	47.3 ms	-14.74%

_{Comparing fix/main-thread-effect-hooks-noop (ebe224d) with main (8c0e483)}

21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

relativeci · 2026-04-03T11:09:19Z

React MTF Example

#233 Bundle Size — 206.05KiB (-0.59%).

ebe224d(current) vs c97d61a main#232(baseline)

Bundle metrics

2 changes

	Current #233	Baseline #232
Initial JS	`0B`	`0B`
Initial CSS	`0B`	`0B`
Cache Invalidation	`46.33%`	`0%`
Chunks	`0`	`0`
Assets	`3`	`3`
Modules	`173`	`173`
Duplicate Modules	`67`	`67`
Duplicate Code	`45.78%`(`-0.02%`)	`45.79%`
Packages	`2`	`2`
Duplicate Packages	`0`	`0`

Bundle size by type

1 change

1 improvement

	Current #233	Baseline #232
IMG	`111.23KiB`	`111.23KiB`
Other	`94.81KiB` (`-1.26%`)	`96.03KiB`

Bundle analysis report Branch fix/main-thread-effect-hooks-noo... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-04-03T11:09:20Z

Web Explorer

#8675 Bundle Size — 728.84KiB (0%).

ebe224d(current) vs c97d61a main#8674(baseline)

Bundle metrics

1 change

	Current #8675	Baseline #8674
Initial JS	`43.31KiB`	`43.31KiB`
Initial CSS	`2.16KiB`	`2.16KiB`
Cache Invalidation	`0%`	`0%`
Chunks	`8`	`8`
Assets	`10`	`10`
Modules	`148`(`-0.67%`)	`149`
Duplicate Modules	`11`	`11`
Duplicate Code	`34.69%`	`34.69%`
Packages	`3`	`3`
Duplicate Packages	`0`	`0`

Bundle size by type no changes

	Current #8675	Baseline #8674
Other	`384.62KiB`	`384.62KiB`
JS	`342.07KiB`	`342.07KiB`
CSS	`2.16KiB`	`2.16KiB`

Bundle analysis report Branch fix/main-thread-effect-hooks-noo... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-04-03T11:09:20Z

React External

#219 Bundle Size — 590.71KiB (-0.13%).

ebe224d(current) vs c97d61a main#218(baseline)

Bundle metrics

1 change

	Current #219	Baseline #218
Initial JS	`0B`	`0B`
Initial CSS	`0B`	`0B`
Cache Invalidation	`31.04%`	`0%`
Chunks	`0`	`0`
Assets	`3`	`3`
Modules	`17`	`17`
Duplicate Modules	`5`	`5`
Duplicate Code	`8.59%`	`8.59%`
Packages	`0`	`0`
Duplicate Packages	`0`	`0`

Bundle size by type

1 change

1 improvement

	Current #219	Baseline #218
Other	`590.71KiB` (`-0.13%`)	`591.5KiB`

Bundle analysis report Branch fix/main-thread-effect-hooks-noo... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-04-03T11:09:21Z

React Example

#7100 Bundle Size — 236.85KiB (-0.35%).

ebe224d(current) vs c97d61a main#7099(baseline)

Bundle metrics

2 changes

	Current #7100	Baseline #7099
Initial JS	`0B`	`0B`
Initial CSS	`0B`	`0B`
Cache Invalidation	`38.67%`	`0%`
Chunks	`0`	`0`
Assets	`4`	`4`
Modules	`179`	`179`
Duplicate Modules	`70`	`70`
Duplicate Code	`46.11%`(`-0.02%`)	`46.12%`
Packages	`2`	`2`
Duplicate Packages	`0`	`0`

Bundle size by type

1 change

1 improvement

	Current #7100	Baseline #7099
IMG	`145.76KiB`	`145.76KiB`
Other	`91.09KiB` (`-0.9%`)	`91.92KiB`

Bundle analysis report Branch fix/main-thread-effect-hooks-noo... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

packages/react/runtime/src/hooks/react.ts

HuJean requested review from Yradex and hzy as code owners April 3, 2026 10:49

coderabbitai bot added the framework:React label Apr 3, 2026

HuJean force-pushed the fix/main-thread-effect-hooks-noop branch from 68e40d1 to c93abfe Compare April 3, 2026 10:52

coderabbitai bot reviewed Apr 3, 2026

View reviewed changes

packages/react/runtime/src/hooks/react.ts Outdated Show resolved Hide resolved

fix: noop effect hooks on main thread

f922cca

HuJean force-pushed the fix/main-thread-effect-hooks-noop branch from c93abfe to f922cca Compare April 3, 2026 11:18

upupming approved these changes Apr 7, 2026

View reviewed changes

packages/react/runtime/src/hooks/react.ts Show resolved Hide resolved

Merge branch 'main' into fix/main-thread-effect-hooks-noop

ebe224d

Yradex approved these changes Apr 7, 2026

View reviewed changes

HuJean merged commit 82046f4 into main Apr 7, 2026
102 of 107 checks passed

HuJean deleted the fix/main-thread-effect-hooks-noop branch April 7, 2026 06:55

github-actions bot mentioned this pull request Apr 7, 2026

chore: Release 2026-04-10 04:17:43 #2430

Open

coderabbitai bot mentioned this pull request Apr 9, 2026

feat: simplify hooks for main-thread runtime #2441

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Summary by CodeRabbit

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Merging this PR will degrade performance by 14.74%

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React MTF Example

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