Sass loader not working in webpack

Question

I am trying to get *.scss files to be supported in my webpack configuration but I keep getting the following error when I run the webpack build command:

ERROR in ./~/css-loader!./~/sass-loader!./app/styles.scss
Module build failed: TypeError: Cannot read property 'sections' of null
at new SourceMapConsumer (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/node_modules/source-map/lib/source-map/source-map-consumer.js:23:21)
at PreviousMap.consumer (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/lib/previous-map.js:37:34)
at new Input (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/lib/input.js:42:28)
at parse (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/lib/parse.js:17:17)
at new LazyResult (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/lib/lazy-result.js:54:47)
at Processor.process (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/node_modules/postcss/lib/processor.js:30:16)
at processCss (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/lib/processCss.js:168:24)
at Object.module.exports (/Users/sean/Development/playground/webpack.sass.test/node_modules/css-loader/lib/loader.js:21:15)
@ ./app/styles.scss 4:14-117

I can't for the life of me figure out why. It's a very basic setup.

I have created a dropbox share with the bare minimum illustrating this: https://www.dropbox.com/s/quobq29ngr38mhx/webpack.sass.test.zip?dl=0

Unzip this then run:

npm install
webpack

Here is my webpack.config.js file:

var path = require('path')
var webpack = require('webpack')

module.exports = {
  devtool: 'eval',
  entry: [
    './app'
  ],
  output: {
    path: path.join(__dirname, 'dist'),
    filename: 'index.js',
    publicPath: '/dist/'
  },
  plugins: [
    new webpack.NoErrorsPlugin()
  ],
  resolve: {
    extensions: ['', '.js']
  },
  module: {
    loaders: [{
      test: /\.scss$/,
      loader: 'style-loader!css-loader!sass-loader'
    }]
  }
}

And the index.js entry file:

require('./styles.scss');

alert('foo bar baz');

And the styles.scss file:

body {
  background-color: #000;
}

It appears to follow the recommendations of the sass-loader documentation site, but I can't get it to run.

:(

Information about my environment:

node - 0.12.4
npm  - 2.10.1
os   - OS X Yosemite

Answer 1

I have managed to get another workaround working that doesn't involve editing the css-loader libraries within my npm_modules directory (as per the answer by @chriserik).

If you add '?sourceMap' to the sass loader the css loader seems to handle the output.

Here is my updated configuration:

var path = require('path')
var webpack = require('webpack')

module.exports = {
  devtool: 'eval',
  entry: [
    './app'
  ],
  output: {
    path: path.join(__dirname, 'dist'),
    filename: 'index.js',
    publicPath: '/dist/'
  },
  plugins: [
    new webpack.NoErrorsPlugin()
  ],
  resolve: {
    extensions: ['', '.js']
  },
  module: {
    loaders: [{
      test: /\.scss$/,
      loader: 'style!css!sass?sourceMap'
    }]
  }
}

P.S. I even expanded this test to include a compass-mixins include, and this worked too.

Answer 2

After having the same issue, I found this: https://github.com/webpack/css-loader/issues/84

Apparently, the solution for now is to manually modify lines 17-19 of /node_modules/css-loader/lib/loader.js with

if(map && typeof map !== "string") {
    map = JSON.stringify(map);
}

This fixed the problem for me.