msw/test/browser/setup/webpackHttpServer.ts

import fs from 'node:fs'
import { WebpackHttpServer } from 'webpack-http-server'
// @ts-expect-error Importing a JavaScript module.
import { SERVICE_WORKER_BUILD_PATH } from '../../../config/constants.js'

declare global {
  var webpackServerPromise: Promise<WebpackHttpServer> | null
}

globalThis.webpackServerPromise = null

export async function getWebpackServer(): Promise<WebpackHttpServer> {
  if (globalThis.webpackServerPromise) {
    return globalThis.webpackServerPromise
  }

  globalThis.webpackServerPromise = startWebpackServer()

  return globalThis.webpackServerPromise
}

async function startWebpackServer(): Promise<WebpackHttpServer> {
  const server = new WebpackHttpServer({
    before(app) {
      // Prevent Express from responding with cached 304 responses.
      app.set('etag', false)

      app.get('/mockServiceWorker.js', (req, res) => {
        res.set('Content-Type', 'application/javascript; charset=utf8')
        res.set('Content-Encoding', 'chunked')

        const readable = fs.createReadStream(SERVICE_WORKER_BUILD_PATH)
        // Apply the worker script patch to forward console messages
        // from the worker to all its clients.
        // readable.push(workerScriptPatch, 'utf8')
        readable.pipe(res)
      })
    },
    webpackConfig: {
      module: {
        rules: [
          {
            test: /\.ts$/,
            use: [
              {
                loader: 'esbuild-loader',
                options: {
                  loader: 'ts',
                  tsconfigRaw: fs.readFileSync(
                    new URL('../../tsconfig.json', import.meta.url),
                  ),
                },
              },
            ],
          },
        ],
      },
      resolve: {
        alias: {
          'msw/browser': new URL(
            '../../../lib/browser/index.mjs',
            import.meta.url,
          ).pathname,
          msw: new URL('../../../lib/core/index.mjs', import.meta.url).pathname,
        },
        extensions: ['.ts', '.js', '.mjs', '.cjs'],
      },
    },
  })

  await server.listen()

  return server
}