react-jss dynamic rules memory leak in strict mode

[ernestostifano]

Expected behavior:
Unreferenced style rules should be properly removed after un-mounting all associated components instances.

Describe the bug:
When React's strict mode is enabled, dynamic rules are not properly removed after un-mounting components, probably because of strict mode's double render (rule keys gets shifted during second render, probably because React Hooks best practices were not followed).

The app ultimately becomes unresponsive.

Reproduction:

https://codesandbox.io/s/happy-joliot-pmmq4d

It is sufficient to mount and un-mount a component with dynamic styles in any React application using strict mode and count the number of attached styles rules.

1. Clone this simple reproduction repo.
2. Checkout this branch: issue/react-jss-no-dynamic-remove
3. Run yarn start
4. Alternately click on Component A and Component B buttons and see how style rules count increases.
5. Remove <StrictMode> from ./src/app.js and repeat step 4. No more leak.

Note: If a custom ID generator is added to print generated classnames, it can be seen how keys increase twice because of strict mode's double render.

Versions (please complete the following information):

• jss: 10.10.0
• Browser: Chrome, Firefox, Safari and Edge (latest versions at the time of submission)
• OS: macOS 13.4

Managing expectations:
I think this is an important bug because it can be easily reproduced and ultimately makes apps unresponsive during development. Also, it was not that simple to pinpoint the source of the memory leak. Should not be that difficult to fix. I would be happy to work on the fix if someone gives me proper context.

Potentially related issues:

• Styles are not removed after unmounting a component #1536
• JSS Dynamic Rules are not removed on re-render V10.0.9 #1616
• [react-jss] 10.0.0-alpha.9 does not remove previously applied styles #1026
• Memory leak with dynamic styles #1360