Error: PostCSS received undefined instead of CSS string

Question

I am using typescript + vue 3 to develop a google chrome extension, when I build my app, shows error like this:

Error: Module build failed (from ./node_modules/vue-loader/dist/stylePostLoader.js):
Error: PostCSS received undefined instead of CSS string

this is the package.json:

{
  "name": "reddwaf-translate-plugin",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "rm -rf src/bundle && webpack --mode development --config src/resource/config/webpack.dev.config.js",
    "build": "gulp --cwd . --gulpfile build/gulp-build.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/jiangxiaoqiang/reddwaf-translate-plugin.git"
  },
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/jiangxiaoqiang/reddwaf-translate-plugin/issues"
  },
  "homepage": "https://github.com/jiangxiaoqiang/reddwaf-translate-plugin#readme",
  "devDependencies": {
    "@babel/core": "^7.16.12",
    "@babel/preset-env": "^7.16.11",
    "@vue/compiler-sfc": "^3.2.29",
    "babel-loader": "^8.2.3",
    "copy-webpack-plugin": "^10.2.1",
    "css-loader": "^6.5.1",
    "html-webpack-plugin": "^5.5.0",
    "mini-css-extract-plugin": "^2.5.3",
    "sass-loader": "^12.4.0",
    "ts-loader": "^9.2.6",
    "typescript": "^4.5.5",
    "vue-loader": "^17.0.0",
    "webpack": "^5.67.0",
    "webpack-cli": "^4.9.2"
  },
  "dependencies": {
    "@types/chrome": "^0.0.177",
    "@types/webextension-polyfill": "^0.8.2",
    "vue": "^3.2.29",
    "vuex": "^4.0.2"
  }
}

and this is the webpack config:

const path = require('path');
const webpack = require( 'webpack' );
const MiniCssExtractPlugin = require( 'mini-css-extract-plugin');
const HtmlWebpackPlugin = require( 'html-webpack-plugin');
const CopyPlugin = require("copy-webpack-plugin");
const { VueLoaderPlugin } = require("vue-loader");

module.exports = {
  entry : {
    'popup/popup' : './src/popup/' 
  } ,
  resolve: {
    extensions: ['.tsx', '.ts', '.js'],
    alias: {
        // https://stackoverflow.com/questions/50805384/module-not-found-error-cant-resolve-vue-path-not-correct
        vue: 'vue/dist/vue.esm-bundler.js'
    },
  },
  output : {
    path : path.resolve(__dirname, '../../bundle') ,
    filename : '[name].js'
  },
  module : {
    rules : [
      {
        test: /\.vue$/,
        loader: 'vue-loader'
      },
      {
        test: /\.ts$/,
        loader: 'ts-loader',
        options: {
          appendTsSuffixTo: [/\.vue$/]
        },
        exclude: /node_modules/
      },
      
      {
        test : /\.js$/ ,
        exclude : [ /node_modules(?!(\/|\\?\\)(translation\.js|selection-widget|connect\.io|chrome-env)\1)/ ] ,
        loader : 'babel-loader'
      } ,
      {
        test: /\.css$/i,
        use: [MiniCssExtractPlugin.loader, "css-loader"],
      },
      {
        test : /\.(scss)$/ ,
        use: [MiniCssExtractPlugin.loader, 'css-loader', 'sass-loader']
      }
    ]
  },
  plugins : [
    new VueLoaderPlugin(),
    new CopyPlugin({
      patterns: [
        { from: "src/manifest.json", to: "manifest.json" },
        { from: "src/resource/image", to: "resource/image" },
      ],
    }),
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css",
    }),
    new HtmlWebpackPlugin({
      filename: 'popup/popup.html',
      template: 'src/popup/index.html'
    }),
    new webpack.DefinePlugin({
      __VUE_OPTIONS_API__: false,
      __VUE_PROD_DEVTOOLS__: false,
    }),
  ]
};

what should I do to fix this problem? I am searching from internet that someone told that the node-sass is not imcompatible, but I am not using node-sass right now. where is the problem?

Answer 1

install sass:

npm i sass

works.