Allow processing of @container at-rule, add tests for it

[vlad-elagin]

Hello!

The name of PR is self-explanatory. My team uses this plugin for a large project, recently we've been updating our UI and tried to use @container rules. And found that the plugin doesn't update variable values inside them.

Here is a quick fix (we'll be grateful for shipping it ASAP 🙏), but generally it would be better to allow user to define which at-rules he wants to be supported. There are a bunch of them.

For example:

// postcss.config.js 
postcss([
  require('postcss-modules-values-replace')({ atRules: ['media', 'container']  })
]);

// index.js in this repo
const defaultAtRules = ['media'];

const factory = ({
  atRules = defaultAtRules,
  // ...
  // ...
  AtRule: {
    ...atRules.reduce((acc, rule) => {
      acc[rule] = function(node) {
        // eslint-disable-next-line no-param-reassign
        node.params = replaceValueSymbols(node.params, definitions);
      }
    }, {}),
    value(node) {
      if (noEmitExports) {
        node.remove();
      }
    },
  },
  // ...

Cheers!

[princed]

Hi Vlad, thank you for the PR!

It looks good to me, apart from the fact it basically presents a breaking change. However, I do like your other suggestion, do you think you can actually implement it in this PR instead? I just don't have capacity for that.

[vlad-elagin]

Sure. What test cases in your opinion should I cover along with that implementation?

[princed]

Thank you!

Sure. What test cases in your opinion should I cover along with that implementation?
A few combinations with different atRules settings, especially overriding the default.

Please make sure to update the README too!

[vlad-elagin]

Done. Let me know if anything else should be done with this new logic

[princed]

This is perfect, thank you!

[princed]

Published as 4.2.0

[princed]

Btw, is anyone using fs setting these days? I feel like it's not possible anymore with modern Webpack, is that true?