Inconsistent CSS resolution order about next.js HOT 10 OPEN

We are seeing the same issue on 14.2.2 where on production builds the CSS styles get included in an unexpected order.

The specific example we are seeing is that CSS styles imported into layout.js are overriding CSS styles set in a component level stylesheet even though they have the same CSS specificity and the component CSS should override the layout's CSS. This bug appears to be due to the order that the CSS is included in the final static .css files that are included in the production build.

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@benjitastic What kind of CSS styling are you using in this case (e.g., css modules)?

No, not modules. Just like this inside the component:

import './styles.css'

Some more details:

In this case layout.js had this at the top:
import '@/styles/customTheme.scss'

And customTheme.scss had this inside it:
@import 'bootstrap/scss/bootstrap';

That bootstrap file has a css style declared for .btn like this:
.btn { padding: .375rem .75rem }

Then in the component we have an element <button className="btn filter-pill"> and that component includes a styles.css. Inside that styles.css there's this declaration: .filter-pill { padding: 8px 33px 8px 14px }

The expectation is that .filter-pill padding can override .btn padding. But .btn was overriding .filter-pill styles. This was because of the 5 /_next/static/css/*.css files appearing in the DOM the 1st one contained .filter-pill and the 2nd one contained .btn. This is backwards from expected order. Regardless of it they are in the same static CSS file or not the .btn declaration should come before the .filter-pill declaration.

Hard to post a repro since I think you need a project that has enough CSS to result in multiple static CSS files being generated.

We reverted back to 14.1.4 and the CSS went back to the correct order.

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It seems 14.2.2 fixed this for development but not for prod.

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@GabenGar Thanks for sharing a —we will be taking a look at this!

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I am seeing this issue as well, particularly for global styles as well as styles using css modules. As mentioned in this issue, it only happens in production builds.

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Setting experimental: { cssChunking: 'strict' } in next.config.js resolves this issue for us. Not ideal, but better than broken CSS ordering in production!

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@benjitastic What kind of CSS styling are you using in this case (e.g., css modules)?

from next.js.

Setting experimental: { cssChunking: 'strict' } in next.config.js resolves this issue for us. Not ideal, but better than broken CSS ordering in production!

Interesting -- I can't find any docs anywhere on the cssChunking parameter.

Does anybody know exactly what "strict" css chunking does?

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Setting experimental: { cssChunking: 'strict' } in next.config.js resolves this issue for us. Not ideal, but better than broken CSS ordering in production!

It does not seem to resolve the issue for us :(

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Are there any updates on this issue from the nextjs team?

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