Dev Server has been initialized using an options object that does not match the API schema

Question

I'm getting the following error after upgrading angular 8 to 9,

        An unhandled exception occurred: Invalid options object. Dev Server has been 
          initialized using an options object that does not match the API schema.
           - options has an unknown property 'contentBase'. These properties are 
          valid:
            object { allowedHosts?, bonjour?, client?, compress?, devMiddleware?, 
          headers?, historyApiFallback?, host?, hot?, http2?, https?, ipc?, 
          liveReload?, magicHtml?, onAfterSetupMiddleware?, 
           See "/private/var/folders/fp/tmjy2_2j15s50f6qpyj6x6mm0000gr/T/ng- 
           xbMtW3/angular-errors.log" for further details.

From what i've read i understood it's something to do with webpack - since i don't have experience with webpack configuration - i don't really know where to begin.

Here is my webpack.config.js

    'use strict';
const path = require('path');
const SpritesmithPlugin = require('webpack-spritesmith');

const plugins = [
  new SpritesmithPlugin({
    src: {
      cwd: path.resolve(__dirname, 'src/styles/icons'),
      glob: '*.png'
    },
    target: {
      image: path.resolve(__dirname, 'src/assets/images/sprite.png'),
      css: path.resolve(__dirname, 'src/styles/_ui-sprite.scss')
    },
    apiOptions: {
      cssImageRef: "assets\/images\/sprite.png",
      generateSpriteName: function (sprite) {
        return 'icon-' + path.basename(sprite, '.png');
      }
    }
  })
];

module.exports = {
  context: __dirname,
  mode: 'development',
  entry: {'doNotTouch': './doNotTouch.ts'},

  output: {
    path: __dirname,
    filename: '[name].js'
  },

  plugins: plugins,

  module: {
    rules: []
  }
};

Answer 1

It most likely has to do with conflicting versions of a module you downloaded on different folders.

Delete all your node modules and web packages and reinstall them.