Are you using 3rd party styling library like antd, bootstrap or anything else?

Like mentioned in the related issue webpack-contrib/mini-css-extract-plugin#250 (comment) the problem should not just be ignored by disabling and hiding the warnings but addressing the source cause instead, its not healthy to have fragile and inconsistent builds.

@dviry fyi I solved this by importing all CSS from a single file, and for code-split styles I'll migrate to a CSS-in-JS approach (probably Glamor styled-components).

Yeah, this is a very valid problem. A light change in your code could alter the cascading effects of your CSS, so this is warranted. Maybe some docs on how to fix it would be nice.

@Timer This seems like more than a documentation problem. I'm working on un-ejecting, but couldn't before 2.0 because of using Sass and CSS modules. Now with 2.0, I'm getting a bunch of these warnings, but we are using CSS modules for everything so there's no chance of the order actually being important (we aren't using any global styles -- just CSS classes).

In our case, I've worked around this by importing within index.js the components that directly use the CSS files that the warnings were complaining about. This resolves the order ambiguity and in my case, the components are shared pieces that are fine to be in my "main" chunk.

I also have this problem, and the error message is utterly useless and frustrating. On a large project it isn't feasible to randomly start requiring the devs to update their CSS based on arbitrary rules.

I'm using this with SCSS, and I'm even more confused on what it wants from me. The linked issue doesn't help much either.

chunk 0 [mini-css-extract-plugin]
Conflicting order between:
 * css ./node_modules/css-loader??ref--6-oneOf-4-1!./node_modules/postcss-loader/src??postcss!./src/form.module.css
 * css ./node_modules/css-loader??ref--6-oneOf-4-1!./node_modules/postcss-loader/src??postcss!./src/components/Footer/Footer.module.css

We use CSS Modules. The problem is in our code, but it is hard to understand what exactly is the issue. It complains about order of css imports in asset graph, but which exactly files?

Related webpack-contrib/mini-css-extract-plugin#250

I also had an issue with the mini-css-extract-plugin warning about a confliction order. Good thing was I'm in complete control of the component library we are using. But finding the correct spot where the problem occurs was really tough. I'm not an expert regarding webpack and neither the mini-css-extract-plugin or any of this. That's why I use CRA in the first place - I don't want to deal in detail with webpack and it's plugin ecosystem.

Nonetheless I was able to fix my component library. I'll just leave this here, so it may be some help to others hopefully.

Before the change:

BaseButton.js

import React from 'react';
import classnames from '../../../classnames';

import '../../../global/Global.css';
import './BaseButton.css';

export default function BaseButton({ children, type, className, ...other }) {
  return (
    <button
      className={classnames('base-button', className)}
      type={type}
      {...other}
    >
      {children}
    </button>
  );
}
BaseButton.defaultProps = {
  /** the type of the button */
  type: 'button'
};

IconButton.js

import React from 'react';

import BaseButton from '../BaseButton/BaseButton';
import classnames from '../../../classnames';

import '../../../global/Global.css';
import './IconButton.css';

export default function IconButton({ className, ...props }) {
  return (
    <BaseButton className={classnames('icon-button', className)} {...props} />
  );
}

When I used the components in that way, the CSS generated on build was not in the order I suspected it to be. When looking at the code of IconButton.js I would assume that the build process would put BaseButton.css before IconButton.css. But in fact it was in the wrong order ... this led to wrongly applied CSS rules (because cascading). And yeah maybe I should move on to use CSS Modules.

Anyway her my solution - even though I can't explain why this works now:

BaseButton.js

import React from 'react';
import classnames from '../../../classnames';

export default function BaseButton({ children, type, className, ...other }) {
  return (
    <button
      className={classnames('base-button', className)}
      type={type}
      {...other}
    >
      {children}
    </button>
  );
}
BaseButton.defaultProps = {
  /** the type of the button */
  type: 'button'
};

IconButton.js

import React from 'react';

import BaseButton from '../BaseButton/BaseButton';
import classnames from '../../../classnames';

import '../../../global/Global.css';
import '../BaseButton/BaseButton.css';
import './IconButton.css';

export default function IconButton({ className, ...props }) {
  return (
    <BaseButton className={classnames('icon-button', className)} {...props} />
  );
}

Maybe one of you can explain this to me or maybe this even helps you finding a similiar solution on your projects. Just wanted to share ... and this is the first issue I found regarding CRA and mini-css-extract-plugin.

@theZieger what's in Global.css?

@gonzofish some normalize styles but mostly custom properties (CSS variables)