perf(reporter): tear down Scroller scroll listener on reset and reassignment#33607
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…ignment setContainer and __reset could leave multiple scroll handlers on the same container because each setContainer added a new anonymous listener and never called removeEventListener. Use a stable handler plus _listenToScrolls / _stopListeningToScrolls so the previous node is always unsubscribed before attaching to a new container, and __reset unsubscribes before clearing state. Add a unit test for repeated setContainer and extend the test container type so removeEventListener is typed as a Sinon spy.
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remove-scroller-scroll-listener
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| Run duration | 16m 20s |
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| Committer | Jennifer Shehane |
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cacieprins
approved these changes
Apr 22, 2026
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Additional details
Each
setContainerpreviously registered another anonymousscrolllistener with no matching removal, so listener count grew with container reassignment.scrolllisteners whensetContainerruns more than once (or after__reset+setContainer) by pairingaddEventListener/removeEventListenerwith a single stable handler.Note
Medium Risk
Touches core reporter scrolling event wiring; risk is mostly around missed/duplicate listener attachment in edge cases or older environments without
AbortController/removeEventListener, but the change is small and covered by updated unit tests.Overview
Fixes a performance issue in the reporter where calling
scroller.setContainer()multiple times could stackscrollevent listeners on the same DOM node.Scrollernow uses a stable_onContainerScrollhandler and explicitly detaches any existing listener (viaremoveEventListenerand anAbortController) before reattaching, and also detaches on__reset()to avoid leaks during teardown. Tests were updated to modelremoveEventListener, add coverage for repeatedsetContainercalls, and changelog notes the scrolling overhead reduction incypress open.Reviewed by Cursor Bugbot for commit 1941da8. Bugbot is set up for automated code reviews on this repo. Configure here.
Steps to test
cd packages/reporter yarn check-ts yarn lint -- src/lib/scroller.ts cypress/e2e/unit/scroller.cy.ts yarn cypress:run:ct --spec cypress/e2e/unit/scroller.cy.tsHow has the user experience changed?
Improved performance when scrolling in reporter
PR Tasks
cypress-documentation?type definitions?