[CSS REWRITE] [BIG UPDATE] Change how to process CSS about jest-preview HOT 4 OPEN

I think this approach is really promising. (Reduce the test running time, Be able to handle async tasks so we can scale easier in the future,…)
I still have some thoughts about this approach:

• The time for the browser to fully load the CSS of the preview might be longer than current (But I think reducing the test running time is more important).
• We might still need to transform CSS module in the transformer. As I understand, we still need to do the expensive task postcssrc() for every test. What if we process the CSS module in the Jest Preview Dashboard? Then it might take a much longer time for the browser to load CSS fully. (Not sure if the user has enough patience to wait for that). I think this is a trade-off.
• Reducing the time of running postcssrc() might be the problem we need to solve for both approaches (current and new), but it’s probably the really hard one.

To summarize, I think it’s feasible to implement the new approach and will bring more pros than cons.

from jest-preview.

hi, is this on the roadmap? i would like to reduce the runtime in CI or make it only parse css based on some env variable. looks like this rewrite would solve that.

from jest-preview.

Hey @ntt261298, please see my note above on a new approach to handle CSS. It would be great if you can give some of your thoughts. Thanks.

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[Just a note] This can fix #260

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