Next.js production js bundle is not minified - next.js

Question

If I generate production js bundle in my next.js project, it's not minified.
For example white characters are not removed.
package.json
{
"name": "web",
"version": "0.1.0",
"private": true,
"scripts": {
"web": "cross-env NODE_ENV=development node server.js",
"dev": "next",
"devServer": "node server.js",
"build": "next build",
"start": "next start"
},
"dependencies": {
"#zeit/next-css": "^1.0.1",
"apollo-boost": "^0.4.4",
"apollo-upload-client": "^11.0.0",
"body-parser": "^1.19.0",
"cross-env": "^6.0.3",
"express": "^4.17.1",
"graphql": "^14.5.8",
"intl": "^1.2.5",
"js-cookie": "^2.2.1",
"js-cookies": "^1.0.4",
"lodash.chunk": "^4.2.0",
"next": "9.1.2",
"next-cookies": "^2.0.3",
"next-with-apollo": "^4.3.0",
"optimize-css-assets-webpack-plugin": "^6.0.0",
"react": "16.11.0",
"react-apollo": "^3.1.3",
"react-dom": "16.11.0",
"react-image-lightbox": "^5.1.1",
"react-input-range": "^1.3.0",
"react-intl": "^3.6.1",
"react-modal": "^3.11.1",
"react-perfect-scrollbar": "^1.5.3",
"react-slick": "^0.25.2",
"slick-carousel": "^1.8.1"
},
"devDependencies": {
"babel-eslint": "^10.1.0",
"eslint": "^7.25.0",
"eslint-config-airbnb": "^18.2.1",
"eslint-plugin-import": "^2.22.1",
"eslint-plugin-jsx-a11y": "^6.4.1",
"eslint-plugin-react": "^7.23.2",
"eslint-plugin-react-hooks": "^4.2.0"
}
}
next.config.js
const withCSS = require("#zeit/next-css");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
module.exports = withCSS({
webpack(config, options) {
config.optimization.minimizer = [];
config.optimization.minimizer.push(new OptimizeCSSAssetsPlugin({}));
return config;
},
distDir: "build",
});
server.js
const express = require('express');
const next = require('next');
const bodyParser = require("body-parser");
const dev = process.env.NODE_ENV !== undefined;
var app;
if(dev){
app = next({ dev});
}else{
app = next({ dev,conf:{
distDir: 'build'
} });
}
const handle = app.getRequestHandler();
app.prepare().then(() => {
const server = express();
server.use('/Public', express.static(__dirname + '/Public'));
server.use('/.well-known', express.static(__dirname + '/Public'));
server.use(bodyParser.urlencoded({ extended: false }));
server.use(bodyParser.json());
server.get('/', (req, res) => {
return app.render(req, res, '/index');
});
server.get('/robots.txt', (req, res) => {
return app.render(req, res, '/robots');
});
server.get('/sitemap.xml', (req, res) => {
return app.render(req, res, '/sitemap');
});
server.listen(8890, err => {
if (err) throw err
console.log('> Ready on http://localhost:8890')
})
})
If I run npm run build, dev variable in server.js is false.

Answer 1

The issue is on line:
config.optimization.minimizer = [];
Removing this line, minification works.