webpack.config.js

const path = require('path');
const { EnvironmentPlugin, IgnorePlugin } = require('webpack');
const TerserPlugin = require('terser-webpack-plugin');

// Mark our dev dependencies as externals so they don't get included in the webpack bundle.
const { devDependencies } = require('./package.json');
const externals = {};

for (const devDependency of Object.keys(devDependencies)) {
  externals[devDependency] = `commonjs ${devDependency}`;
}

// And anything MikroORM's packaging can be ignored if it's not on disk.
// Later we check these dynamically and tell webpack to ignore the ones we don't have.
const optionalModules = new Set([
  ...Object.keys(require('knex/package.json').browser),
  ...Object.keys(require('@mikro-orm/core/package.json').peerDependencies),
  ...Object.keys(require('@mikro-orm/core/package.json').devDependencies || {}),
]);

module.exports = {
  entry: path.resolve('src', 'main.ts'),

  // You can toggle development mode on to better see what's going on in the webpack bundle,
  // but for anything that is getting deployed, you should use 'production'.
  // mode: 'development',
  mode: 'production',

  optimization: {
    minimizer: [
      new TerserPlugin({
        terserOptions: {
          // We want to minify the bundle, but don't want Terser to change the names of our entity
          // classes. This can be controlled in a more granular way if needed, (see
          // https://terser.org/docs/api-reference.html#mangle-options) but the safest default
          // config is that we simply disable mangling altogether but allow minification to proceed.
          mangle: false,
          // Similarly, Terser's compression may at its own discretion change function and class names.
          // While it only rarely does so, it's safest to also disable changing their names here.
          // This can be controlled in a more granular way if needed (see
          // https://terser.org/docs/api-reference.html#compress-options).
          compress: {
            keep_classnames: true,
            keep_fnames: true,
          },
        },
      }),
    ],
  },
  target: 'node',
  module: {
    rules: [
      // Bring in our typescript files.
      {
        test: /\.ts$/,
        exclude: /node_modules/,
        loader: 'ts-loader',
      },

      // Native modules can be bundled as well.
      {
        test: /\.node$/,
        use: 'node-loader',
      },

      // Some of MikroORM's dependencies use mjs files, so let's set them up here.
      {
        test: /\.mjs$/,
        include: /node_modules/,
        type: 'javascript/auto',
      },
    ],
  },

  // These are computed above.
  externals,

  resolve: {
    extensions: ['.ts', '.js'],
  },

  plugins: [
    // Ignore any of our optional modules if they aren't installed. This ignores database drivers
    // that we aren't using for example.
    new EnvironmentPlugin({ WEBPACK: true }),
    new IgnorePlugin({
      checkResource: (resource) => {
        const baseResource = resource
          .split('/', resource[0] === '@' ? 2 : 1)
          .join('/');

        if (optionalModules.has(baseResource)) {
          try {
            require.resolve(resource);
            return false;
          } catch {
            return true;
          }
        }

        const lazyImports = [
          '@nestjs/microservices',
          '@nestjs/websockets/socket-module',
          'cache-manager',
          '@nestjs/microservices/microservices-module',
          'class-transformer/storage',
          'fastify-swagger',
        ];

        if (!lazyImports.includes(resource)) {
          return false;
        }

        try {
          require.resolve(resource);
        } catch (err) {
          return true;
        }

        return false;
      },
    }),
  ],

  output: {
    filename: 'server.js',
    libraryTarget: 'commonjs',
    path: path.resolve(__dirname, 'output'),
  },
};