GoogleChrome/lighthouse

handling impact of isInputPending on long tasks metrics?

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#11,747 opened on Dec 2, 2020

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P2good first issuemetrics-cwv

Description

navigator.scheduling.isInputPending is shipping by default in current Chrome stable (m87). Without user input, any page using isInputPending has a strong reason to believe yielding during long tasks won't improve user experience so it could keep on chugging instead.

This may have a large impact on any metric looking at long tasks (TBT, TTI) compared to what a real user would experience when loading the same page.

Contributor guide

Tech stack
javascript
Domain
performanceobservability
Issue type
research
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Long Tasks APInavigator.scheduling.isInputPendingTBT metricTTI metric
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the WICG discussion at https://github.com/WICG/is input pending/issues/37 to understand proposed interactions with Long Tasks API. Review Chrome status entry for implementation details. Assess impact on Lighthouse's TBT and TTI audits by considering how isInputPending affects long task duration. Propose whether to incorporate isInputPending detection into existing metrics or add a new audit.