configureWebpack breaks when it is a function

[JessicaSachs]

• I confirm that this is an issue rather than a question.

Bug report

As per the docs (0.x and 1.x), configureWebpack is supposed to take in a function. Currently, when I return an identity function, Vuepress throws errors in Chrome and cannot render.
I'm trying to merge my webpack configuration for vuepress in with my vue-cli + webpack configuration. Currently, when I point vuepress at my source, it fails to find my aliases.
I will resort to trying out Vuepress' webpackChain option to accomplish the same thing.

Steps to reproduce

Repository Link: https://github.com/JessicaSachs/vuepress-broken-configurewebpack

1. Create a Vuepress project with a README.md inside of docs/
2. Add a config.js file with the below contents

module.exports = {
  description: 'My description',
  configureWebpack: config => config, // I print out "config" in the additional info section
};

3. Run the project
4. Open Chrome and the dev tools

What is expected?

Site renders the README file.

What is actually happening?

1. Errors in the chrome console relating to stylus loader
2. Nothing renders

Uncaught Error: Module build failed (from ./node_modules/stylus-loader/index.js):
ParseError: /Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/plugin-nprogress/nprogress.styl:4:194
   1| // style-loader: Adds some css to the DOM by adding a <style> tag
   2| 
   3| // load the styles
   4| var content = require("!!../../css-loader/dist/cjs.js??ref--29-oneOf-1-1!../../postcss-loader/src/index.js??ref--29-oneOf-1-2!../../stylus-loader/index.js??ref--29-oneOf-1-3!./nprogress.styl");
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------^
   5| if(typeof content === 'string') content = [[module.id, content, '']];
   6| if(content.locals) module.exports = content.locals;
   7| // add the styles to the DOM

expected "indent", got ";"

    at Parser.error (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:259)
    at Parser.expect (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:287)
    at Parser.block (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:845)
    at Parser.selector (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:1555)
    at Parser.ident (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:1446)
    at Parser.stmt (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:778)
    at Parser.statement (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:685)
    at Parser.parse (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/parser.js:236)
    at Renderer.render (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus/lib/renderer.js:80)
    at /Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/stylus-loader/index.js:167
    at tryCatchReject (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/makePromise.js:840)
    at runContinuation1 (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/makePromise.js:799)
    at Fulfilled.when (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/makePromise.js:590)
    at Pending.run (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/makePromise.js:481)
    at Scheduler._drain (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/Scheduler.js:62)
    at Scheduler.drain (/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/when/lib/Scheduler.js:27)
    at eval (cjs.js?!./node_modules/postcss-loader/src/index.js?!./node_modules/stylus-loader/index.js?!./node_modules/vue-style-loader/index.js!./node_modules/css-loader/dist/cjs.js?!./node_modules/postcss-loader/src/index.js?!./node_modules/stylus-loader/index.js?!./node_modules/@vuepress/plugin-nprogress/nprogress.styl:1)
    at Object../node_modules/css-loader/dist/cjs.js?!./node_modules/postcss-loader/src/index.js?!./node_modules/stylus-loader/index.js?!./node_modules/vue-style-loader/index.js!./node_modules/css-loader/dist/cjs.js?!./node_modules/postcss-loader/src/index.js?!./node_modules/stylus-loader/index.js?!./node_modules/@vuepress/plugin-nprogress/nprogress.styl (app.js:4559)
    at __webpack_require__ (app.js:1476)
    at fn (app.js:833)
    at eval (nprogress.styl?932b:4)
    at Object../node_modules/@vuepress/plugin-nprogress/nprogress.styl (app.js:2242)
    at __webpack_require__ (app.js:1476)
    at fn (app.js:833)
    at eval (enhanceAppFile.js?64a0:1)
    at Module../node_modules/@vuepress/plugin-nprogress/enhanceAppFile.js (app.js:2231)

Other relevant information

• Adding the appropriate "stylus" files does not fix the issue
• Output of npx vuepress info in my VuePress project:

Environment Info:

  System:
    OS: macOS 10.14
    CPU: (8) x64 Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
  Binaries:
    Node: 10.14.2 - /usr/local/bin/node
    Yarn: 1.13.0 - /usr/local/bin/yarn
    npm: 6.10.0 - /usr/local/bin/npm
  Browsers:
    Chrome: Not Found // I'm currently writing this issue on Chrome 75. This must be broken.
    Firefox: 68.0.1
    Safari: 12.0
  npmPackages:
    @vuepress/core:  1.0.3 
    @vuepress/theme-default:  1.0.3 
    vuepress: ^1.0.3 => 1.0.3 
  npmGlobalPackages:
    vuepress: Not Found

• console.log(webpackConfig)

{ mode: 'development',
  devtool: 'cheap-module-eval-source-map',
  node:
   { setImmediate: false,
     global: false,
     process: false,
     dgram: 'empty',
     fs: 'empty',
     net: 'empty',
     tls: 'empty',
     child_process: 'empty' },
  output:
   { path:
      '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/docs/.vuepress/dist',
     filename: 'assets/js/[name].js',
     publicPath: '/' },
  resolve:
   { symlinks: true,
     alias:
      { '@source':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/docs',
        '@client':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/client',
        '@app':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/client',
        '@temp':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/.temp',
        '@dynamic':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/.temp/dynamic',
        '@internal':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/.temp/internal',
        '@transform':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/.temp/transform',
        '@AlgoliaSearchBox':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/noopModule.js',
        '@SearchBox':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/plugin-search/SearchBox.vue',
        '@current-theme':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default',
        '@theme/components/AlgoliaSearchBox.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/AlgoliaSearchBox.vue',
        '@theme/components/DropdownLink.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/DropdownLink.vue',
        '@theme/components/DropdownTransition.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/DropdownTransition.vue',
        '@theme/components/Home.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/Home.vue',
        '@theme/components/NavLink.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/NavLink.vue',
        '@theme/components/NavLinks.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/NavLinks.vue',
        '@theme/components/Navbar.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/Navbar.vue',
        '@theme/components/Page.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/Page.vue',
        '@theme/components/Sidebar.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/Sidebar.vue',
        '@theme/components/SidebarButton.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/SidebarButton.vue',
        '@theme/components/SidebarGroup.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/SidebarGroup.vue',
        '@theme/components/SidebarLink.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/SidebarLink.vue',
        '@theme/components/SidebarLinks.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/components/SidebarLinks.vue',
        '@theme/layouts/404.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/layouts/404.vue',
        '@theme/layouts/Layout.vue':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default/layouts/Layout.vue',
        '@theme':
         '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/theme-default' },
     extensions: [ '.js', '.jsx', '.vue', '.json', '.styl' ],
     modules:
      [ '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node/webpack/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules',
        '/Users/jessicasachs/projects/node_modules',
        '/Users/jessicasachs/node_modules',
        '/Users/node_modules',
        '/node_modules' ] },
  resolveLoader:
   { symlinks: true,
     modules:
      [ '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node/webpack/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/node_modules',
        '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules',
        '/Users/jessicasachs/projects/node_modules',
        '/Users/jessicasachs/node_modules',
        '/Users/node_modules',
        '/node_modules' ] },
  module:
   { noParse: /^(vue|vue-router|vuex|vuex-router-sync)$/,
     rules:
      [ [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object] ] },
  plugins:
   [ VueLoaderPlugin {},
     DefinePlugin { definitions: [Object] },
     HotModuleReplacementPlugin {
       options: {},
       multiStep: undefined,
       fullBuildTimeout: 200,
       requestTimeout: 10000 },
     WebpackBarPlugin {
       profile: false,
       handler: [Function],
       modulesCount: 500,
       showEntries: false,
       showModules: true,
       showActiveModules: true,
       options: [Object],
       reporters: [Array] },
     HtmlWebpackPlugin { options: [Object] },
     HeadPlugin { tags: [] },
     DevLogPlugin { options: [Object] } ],
  entry:
   { app:
      [ '/Users/jessicasachs/projects/vuepress-configure-webpack-broken/node_modules/@vuepress/core/lib/client/clientEntry.js' ] } }