title: Using Webpack 2 and extract-text-webpack-plugin
body: <p>I'm using extract-text-webpack-plugin 2.0.0-rc.3 with Webpack 2.2.1 and am getting this error when running the build:</p>
  
  <pre><code>/node_modules/extract-text-webpack-plugin/index.js:259
  var shouldExtract = !!(options.allChunks || chunk.isInitial());
                                                    ^
  TypeError: chunk.isInitial is not a function
  </code></pre>
  
  <p>Here is my webpack.config.js:</p>
  
  <pre class="lang-js prettyprint-override"><code>'use strict';
  const argv = require('yargs').argv;
  const ExtractTextPlugin = require("extract-text-webpack-plugin");
  const webpack = require('webpack');
  
  module.exports = (function () {
    let config = {
      entry   : './' + process.env.npm_package_config_paths_source + '/main.js',
      output  : {
        filename : 'main.js'
      },
      watch   : !!argv.watch,
      vue     : {
        loaders : {
          js   : 'babel-loader',
          // Create separate CSS file to prevent unstyled content
          sass : ExtractTextPlugin.extract("css!sass?sourceMap") // requires `devtool: "#source-map"`
        }
      },
      module  : {
        rules : [
          {
            test    : /\.js$/,
            use     : 'babel-loader',
            exclude : '/node_modules/'
          },
          {
            test    : /\.vue$/,
            use     : 'vue-loader',
            options : {
              loaders : {
                'scss' : 'vue-style-loader!css-loader!sass-loader',
                'sass' : 'vue-style-loader!css-loader!sass-loader?indentedSyntax'
              },
            }
          }
        ]
      },
      plugins : [
        new webpack.DefinePlugin({
          'process.env' : {
            npm_package_config_paths_source : '"' + process.env.npm_package_config_paths_source + '"'
          }
        }),
        new ExtractTextPlugin("style.css")
      ],
      resolve : {
        alias : {
          'vue$' : 'vue/dist/vue.common.js'
        }
      },
      babel   : {
        "presets"  : ["es2015", "stage-2"],
        "comments" : false,
        "env"      : {
          "test" : {
            "plugins" : ["istanbul"]
          }
        }
      },
      devtool : "#source-map" // #eval-source-map is faster but not compatible with ExtractTextPlugin
    };
  
    if (process.env.NODE_ENV === 'production') {
      config.plugins = [
        // short-circuits all Vue.js warning code
        new webpack.DefinePlugin({
          'process.env' : {
            NODE_ENV                        : '"production"',
            npm_package_config_paths_source : '"' + process.env.npm_package_config_paths_source + '"'
          }
        }),
        // minify with dead-code elimination
        new webpack.optimize.UglifyJsPlugin(),
        new ExtractTextPlugin("style.css")
      ];
      config.devtool = "#source-map";
    }
  
    return config;
  })();
  </code></pre>
  
  <p>When I remove <code>new ExtractTextPlugin("style.css")</code> from the <code>plugins</code> array the build runs fine, but doesn't create <code>style.css</code>.</p>
  
  <p>If I add the <code>allChunks: true</code> option the error becomes this:</p>
  
  <pre><code>/node_modules/webpack/lib/Chunk.js:80
  return this.entrypoints.length &gt; 0;
                         ^
  TypeError: Cannot read property 'length' of undefined
  </code></pre>