fix(core): scroll-spy race conditions on rapid/smooth scroll#2968
Merged
bennypowers merged 3 commits intomainfrom Mar 8, 2026
Merged
fix(core): scroll-spy race conditions on rapid/smooth scroll#2968bennypowers merged 3 commits intomainfrom
bennypowers merged 3 commits intomainfrom
Conversation
Fixes three bugs in ScrollSpyController: 1. Rapid clicks: setActive() now cancels previous force state via AbortController before establishing new force, preventing stale listeners from releasing force prematurely. 2. Force release timing: replaced await-first-intersection approach with scrollend event listener (+ 3s safety timeout). The old approach released force when any IO fired during smooth scroll, causing intermediate sections to steal the active state. 3. Non-contiguous sections: passedLinks are now sorted by DOM order instead of relying on Set insertion order, which was unreliable when sections had untracked content between them. Also fixes a safeguard bug where the #nextIntersection timeout set `#intersected = false` (should be `true`), which could cause an infinite rAF loop, and fixes the boundary comparison to use rootBounds.top instead of intersectionRect.top so elements exactly at the viewport top are correctly considered "passed". Closes #2911 Closes #2920 Assisted-By: Claude Opus 4.6 <noreply@anthropic.com>
🦋 Changeset detectedLatest commit: fa1ed38 The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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 |
✅ Deploy Preview for patternfly-elements ready!
To edit notification comments on pull requests, go to your Netlify site settings. |
Contributor
✅ Commitlint tests passed!More Info{
"valid": true,
"errors": [],
"warnings": [],
"input": "fix(core): scroll-spy race conditions on rapid/smooth scroll"
} |
Assisted-By: Claude Opus 4.6 <noreply@anthropic.com>
Contributor
There was a problem hiding this comment.
Pull request overview
Fixes ScrollSpyController race conditions that could cause jump-links components to show incorrect active state during rapid and/or smooth scrolling navigation, and adds unit coverage to prevent regressions.
Changes:
- Add force-mode cancellation/cleanup and switch force release from “first IO callback” to
scrollend(with timeout fallback). - Fix intersection wait-loop safeguard and adjust “passed” boundary detection.
- Add a dedicated
ScrollSpyControllertest suite covering rapid clicks, smooth scrolling, and non-contiguous sections.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| core/pfe-core/controllers/scroll-spy-controller.ts | Updates force-mode lifecycle, passed-link ordering, and intersection/threshold logic to prevent active-state races. |
| core/pfe-core/test/scroll-spy-controller.spec.ts | Adds 9 integration-style unit tests validating correct active state across scroll/navigation scenarios. |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
You can also share your feedback on Copilot code review. Take the survey.
Prevents a stale 3s timeout from prematurely resolving a subsequent #nextIntersection() call. Assisted-By: Claude Opus 4.6 <noreply@anthropic.com>
This comment has been minimized.
This comment has been minimized.
This was referenced Mar 8, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Fixes race conditions in
ScrollSpyControllerthat causedpf-jump-linksandrh-jump-linksto show incorrect active state during navigation:setActive()now aborts any pending force-release listeners viaAbortControllerbefore establishing new force, so rapid successive clicks don't leave stale listeners that release force prematurelyscrollendinstead of first IO — The old approach released force when anyIntersectionObservercallback fired, which during smooth scroll meant intermediate sections could steal the active state. Now waits forscrollend(with 3s safety timeout)passedLinkssorted by DOM order — Previously relied onSetinsertion order, which was wrong when scrolling back through non-contiguous sections (sections with untracked content between them)#nextIntersectiontimeout — Was setting#intersected = false(should betrue), which could cause an infinite rAF loop if no IO firesrootBounds.topinstead ofintersectionRect.topso elements exactly at the viewport top are correctly considered "passed"Closes #2911
Closes #2920
Resolves RedHat-UX/red-hat-design-system#2425
Resolves RedHat-UX/red-hat-design-system#2474
Test plan
scroll-spy-controller.spec.ts(all pass)rh-jump-linkscomponent in RHDS dev server (7/8 pass — the 1 "failure" is expected async timing, identical on original controller)🤖 Generated with Claude Code