:global() css-module 选择器在 NextJS 中不是纯的问题

Question

So I'm migrating an app from CRA to NextJS and I have encountered an error for the .module.scss files of some components and pages:

Syntax error: Selector ":global(.label-primary)" is not pure (pure selectors must contain at least one local class or id)

I get this error for all the :global and :local css-module selectors. Based on what I have searched I can fix this issue by wrapping the selector in a class and editing the jsx aswell. but wouldn't that defeat it's purpose? And how is this working on the CRA version of the app and not on NextJS?

EDIT: One solution I have for this is moving :global() selectors to the global css files that are imported in _app.js but my question is that is there any way that we can have so these styles would be usable like they are right now ( :global(...) )?

Answer 1

No there isn't any solution as of yet other than overriding the webpack config itself. It was working in CRA because they probably have mode : local , while Next.js has pure .

---

I haven't tried overriding css-loader webpack config, so I am simply suggesting a workaround. Since, you are using SCSS, you can wrap your pseudo-global ^[1] styles like this:

.root :global {
  .foo {
    color: red;
  }
}

Now wrap your component/page in a div and set the class as styles.root on that element. Then, on all the child elements you can directly set className="foo" .

import styles from "../styles/index.module.scss";

const IndexPage = () => (
  <div className={styles.root}>
    <div className="foo">This text should be red!</div>
  </div>
);

export default IndexPage;

Note that, you need to consider issues regarding specificity after this method, also this doesn't directly work with animations, you need to separate the keyframes and then make them global.

Demo Sandbox

---

[1]: This method doesn't make the styles truly global as the styles are still scoped. The class foo will work only when some parent has styles.root as class. This is preferrable only if you didn't intend to use your :global(.selector) from other components, and were using them just because you wanted to manipulate the class names using JS without the styles object.

If you want these to be truly global, add styles.root to document.documentElement in an useEffect hook like this:

import { useEffect } from "react";
import styles from "../styles/index.module.scss";

const IndexPage = () => {
  useEffect(() => {
    document.documentElement.classList.add(styles.root);
    return () => {
      document.documentElement.classList.remove(styles.root);
    };
  }, []);

  return (
    <div className="foo">
      This text should be red, even if you put it in another component until the
      page is same. If you want it across pages inject it in _app or _document.
    </div>
  );
};

export default IndexPage;

Demo Sandbox

PS: Injecting class to html in _app or _document is not exactly same as using a global stylesheet , as it may happen that you have multi-page application, then only the CSS of the components on a particular page will be requested because of automatic CSS code-splitting done by Next.js. If that's not the case and all your pages share same CSS, then there is no need to complicate things, just go with the conventional method of importing styles in _app .

Answer 2

I had the same problem, the right writing is

.root:global {
   color:red
}