cssinjs/jss

themed useCreateStyles leaks style tags in StrictMode

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#1332 opened on Apr 20, 2020

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bughelp wanted

Description

Expected behavior: <style> elements get disposed when re-rendering in StrictMode.

Describe the bug: When using themed styles (possibly prop-based as well) re-rendering a component using useStyles with a new theme will leak their <style> elements.

This is possibly due to useStyles managing the sheet during render but unmanaging it in a effect cleanup. A component can render multiple times (in concurrent and strict mode) before an effect is scheduled.

Codesandbox link: https://codesandbox.io/s/determined-wood-8d0s7?file=/src/App.js:513-622

Click "rerender" and see that the number of <style> element grows with every "rerender" click.

Versions (please complete the following information):

  • react-jss: 10.1.1
  • Browser [e.g. chrome, safari]: Chrome 81
  • OS [e.g. Windows, macOS]: Ubuntu 18.04
  • react: 16.13.1

Contributor guide

Tech stack
javascriptreact
Domain
frontend
Issue type
bug
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.
1-2 days
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.
clear
Prerequisites
React StrictModejss library
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Focus on the `useStyles` hook in react jss. Investigate how it creates and disposes style sheets during render and effects. The bug likely arises because sheets are created during render but only disposed in an effect cleanup, which conflicts with React's StrictMode double rendering. Study the codesandbox reproduction and the relevant source files in the jss repository to understand the timing. Consider proposing to move sheet management to a side effect or use a ref to track renders.