Emotion: JSX pragma slow in dev mode

[pomber]

Current behavior:

In dev mode, using the jsx pragma, my app is taking several seconds to render.

To reproduce:

Render an app with a lot of react elements using the jsx pragma

Environment information:

• react version: 16.8.6
• @emotion/core version: 10.0.14

Actually, I'm using it via theme-ui with the sx prop, but after profiling I found the bottleneck is this line from emotion core:

I'm creating the issue just in case there's some easy optimization to replace the new Error bottleneck. Feel free to close it otherwise.

[Andarist]

Do you observe decreased performance on initial render, on rerenders or on both?

[pomber]

on initial render, but i'm not rerendering the elements so I'm not sure if it's the same or not.

[Andarist]

Would you be willing to make a small experiment? Would be great to introduce a simple Map-based caching (using type as key) for those stack-retrieved labels. I wonder if that would help.

[Andarist]

I've tried but I can't repro this, for this to get fixed (or handled somehow) you'd have to share a repro case, share your environment (versions etc). Closing this for now as no enough information has been shared - but feel free to ask for reopening or just open a new issue if you still suffer from this.

[itsUndefined]

I am experiencing the same issue. Both on initial render and on rerenders. Having to render 3 divs with css prop takes 2.5ms on development and 0.015ms on production.