Old performance issue not fixed ( development only )

Current behavior: Performance difference between development and production is very different when using jsx pragma. Issue probably has to do with #1467

In one of my material-ui projects I get the following numbers in development: and the following in production: Performance difference is almost 150 times slower. The screenshots are from only 3 material-ui elements that are rendering.

To reproduce:

1. Use a chromium based browser to get a highly accurate timer on the console
2. Go to https://codesandbox.io/s/emotion-issue-template-forked-my9lw
3. Click on rerender and watch console for time it took to run jsx code in development.
4. Uncomment line 13 to set NODE_ENV environment to production
5. Click on rerender and watch console for time compared to step 3

Expected behavior: I expected the performance difference to be at the worst case scenario 2x times slower

Environment information:

• react version: 17.0.1
• @emotion/react version: 11.1.5

[Andarist]

For the time being I suggest using patch-package to disable that part of the code.

I’ll be investigating this - I’d like to understand why this is slow for you first. After I get a better understanding the issue will get either fixed or some kind of an opt-out flag will be added (I don’t completely put off the table dropping this code entirely either).

[Andarist]

I’m slammed with work right now so I won’t be able to look into it soon. It would be appreciated if you could dig into this deeper to assess what’s the problem.