Add support for preprocessing with node-sass

[smably]

Inspired by the great work done by @RDGthree in #90, I added some logic to allow a special node-sass syntax type. This adds a step wherein the file is pre-processed by node-sass before being passed as plain CSS to postcss.

This allows the babel plugin to be used with webpack's sass-loader, which uses a custom importer to handle @imports from node_modules. I added an importer config option that takes a single importer or an array of importers. For example:

"plugins": [
  ["react-css-modules", {
    "filetypes": {
      ".scss": {
        "syntax": "node-sass",
        "importer": "node-sass-tilde-importer"
      }
    }
  }]
]

I've also published these changes as a fork (babel-plugin-react-css-modules-sass on npm / https://github.com/smably/babel-plugin-react-css-modules-sass on GitHub).

If there's a chance of this getting merged upstream, I'd be happy to add tests or otherwise clean this up.

[gajus]

What issue does this fix that currently cannot be fixed using postcss?

[smably]

@gajus This is to handle sass-loader's custom syntax for imports from node_modules, e.g.:

@import "~bootstrap/dist/css/bootstrap";

I'm not aware of a way do this with postcss alone. I'm guessing that nearly everyone who uses this babel plugin with Sass files will be bundling using sass-loader, so I think it makes sense to use the same pre-processor in the babel plugin as the webpack loader to ensure that the output is in sync.

[smably]

Going to close this out as it's quite old and doesn't look like it's likely to be merged.

[Lighttree]

Hi, does this project maintained by someone ? This PR fixes quite important issue for Sass users, will this be merged ?