webpack.config.js

const webpackConfig = require('./node_modules/@ionic/app-scripts/config/webpack.config');

const vueAlias = {
  extensions: ['.ts', '.js', '.vue', '.json'],
  alias: {
    'vue$': 'vue/dist/vue.esm.js'
  }
};

const vueRule = {
  test: /\.vue$/,
  loader: 'vue-loader',
  options: {
    // Since sass-loader (weirdly) has SCSS as its default parse mode, we map the
    // "scss" and "sass" values for the lang attribute to the right configs here.
    // other preprocessors should work out of the box, no loader config like this
    // necessary.
    'scss': [
      'vue-style-loader', 'css-loader', 'sass-loader'
    ],
    'sass': ['vue-style-loader', 'css-loader', 'sass-loader?indentedSyntax']
  }
  // other vue-loader options go here
};
webpackConfig.dev.module.loaders.push(vueRule)

webpackConfig.dev.resolve = Object.assign(webpackConfig.dev.resolve, vueAlias)