feat: support webpack-dev-server v4

npm/angular/package.json

@@ -62,7 +62,7 @@
     "tslib": "^2.2.0",
     "tslint": "5.20.1",
     "typescript": "4.2.4",
-    "webpack-dev-server": "3.11.2",
+    "webpack-dev-server": "4.0.0",
     "zone.js": "0.11.4"
   },
   "peerDependencies": {

npm/webpack-dev-server/package.json

@@ -6,7 +6,8 @@
   "scripts": {
     "build": "tsc",
     "build-prod": "tsc",
-    "test": "tsc && mocha -r @packages/ts/register test/**/*.spec.ts test/*.spec.ts --exit",
+    "test": "node ./test-wds-3.js",
+    "test-all": "tsc && mocha -r @packages/ts/register test/**/*.spec.ts test/*.spec.ts --exit",
     "watch": "tsc -w"
   },
   "dependencies": {
@@ -16,15 +17,15 @@
   },
   "devDependencies": {
     "@types/webpack": ">=4",
-    "@types/webpack-dev-server": "^3.11.1",
+    "@types/webpack-dev-server": "^4.0.0",
     "chai": "^4.2.0",
     "html-webpack-plugin": "4.x",
     "mocha": "^8.1.3",
     "snap-shot-it": "7.9.3",
     "speed-measure-webpack-plugin": "1.4.2",
     "typescript": "^4.2.3",
     "webpack": "^4.44.2",
-    "webpack-dev-server": "^3.11.0"
+    "webpack-dev-server": "^4.0.0"
   },
   "peerDependencies": {
     "html-webpack-plugin": ">=4",

npm/webpack-dev-server/src/index.ts

@@ -2,6 +2,7 @@ import { debug as debugFn } from 'debug'
 import { AddressInfo } from 'net'
 import { Server } from 'http'
 import { start as createDevServer, StartDevServer } from './startServer'
+import { webpackDevServerFacts } from './webpackDevServerFacts'
 
 const debug = debugFn('cypress:webpack-dev-server:webpack')
 
@@ -17,26 +18,41 @@ export { StartDevServer }
 export async function startDevServer (startDevServerArgs: StartDevServer, exitProcess = process.exit) {
   const webpackDevServer = await createDevServer(startDevServerArgs, exitProcess)
 
-  return new Promise<ResolvedDevServerConfig>((resolve) => {
-    const httpSvr = webpackDevServer.listen(0, '127.0.0.1', () => {
-      // webpack-dev-server v3 returns `http.Server`.
-      // v4 returns a Promise that resolves `http.Server`.
-      // use Promise.resolve to make sure we get the `http.Server`,
-      // regardless of webpack-dev-server version.
-      Promise.resolve(httpSvr).then((server: Server) => {
+  return new Promise<ResolvedDevServerConfig>(async (resolve, reject) => {
+    if (webpackDevServerFacts.isV3()) {
+      const server: Server = webpackDevServer.listen(0, '127.0.0.1', () => {
         // FIXME: handle address returning a string
         const port = (server.address() as AddressInfo).port
 
         debug('Component testing webpack server started on port', port)
 
-        return resolve({
+        resolve({
           port,
           close: (done?: DoneCallback) => {
-            httpSvr.close()
+            server.close()
             done?.()
           },
         })
       })
-    })
+
+      return
+    }
+
+    if (webpackDevServerFacts.isV4()) {
+      await webpackDevServer.start()
+
+      resolve({
+        // @ts-expect-error @types do not yet support v4
+        port: webpackDevServer.options.port,
+        close: (done?: DoneCallback) => {
+          webpackDevServer.stop()
+          done?.()
+        },
+      })
+
+      return
+    }
+
+    reject(webpackDevServerFacts.unsupported())
   })
 }

npm/webpack-dev-server/src/startServer.ts

@@ -1,8 +1,8 @@
 import Debug from 'debug'
 import webpack from 'webpack'
 import WebpackDevServer from 'webpack-dev-server'
-import webpackDevServerPkg from 'webpack-dev-server/package.json'
 import { makeWebpackConfig, UserWebpackDevServerOptions } from './makeWebpackConfig'
+import { webpackDevServerFacts } from './webpackDevServerFacts'
 
 export interface StartDevServer extends UserWebpackDevServerOptions {
   /* this is the Cypress options object */
@@ -53,25 +53,33 @@ export async function start ({ webpackConfig: userWebpackConfig, template, optio
     hot: false,
   }
 
-  if (webpackDevServerPkg.version.match(/3\./)) {
+  if (webpackDevServerFacts.isV3()) {
     webpackDevServerConfig = {
       ...webpackDevServerConfig,
+      // @ts-expect-error ignore webpack-dev-server v3 type errors
       inline: false,
       publicPath: devServerPublicPathRoute,
       noInfo: false,
     }
-  } else if (webpackDevServerPkg.version.match(/4\./)) {
+
+    // @ts-expect-error ignore webpack-dev-server v3 type errors
+    return new WebpackDevServer(compiler, webpackDevServerConfig)
+  }
+
+  if (webpackDevServerFacts.isV4()) {
     webpackDevServerConfig = {
+      host: 'localhost',
+      port: 'auto',
       ...userWebpackConfig?.devServer,
       devMiddleware: {
         publicPath: devServerPublicPathRoute,
       },
       hot: false,
     }
-  } else {
-    throw Error(`@cypress/webpack-dev-server only supports webpack-dev-server v3 and v4. Found: ${webpackDevServerPkg.version}.`)
+
+    // @ts-expect-error Webpack types are clashing between Webpack and WebpackDevServer
+    return new WebpackDevServer(webpackDevServerConfig, compiler)
   }
 
-  // @ts-ignore types for webpack v5 are incorrect?
-  return new WebpackDevServer(compiler, webpackDevServerConfig)
+  throw webpackDevServerFacts.unsupported()
 }

npm/webpack-dev-server/src/webpackDevServerFacts.ts

@@ -0,0 +1,14 @@
+import webpackDevServerPkg from 'webpack-dev-server/package.json'
+
+export const webpackDevServerFacts = {
+  version: webpackDevServerPkg.version,
+  isV3 (version = webpackDevServerPkg.version) {
+    return /^3\./.test(version)
+  },
+  isV4 (version = webpackDevServerPkg.version) {
+    return /^4\./.test(version)
+  },
+  unsupported () {
+    return Error(`@cypress/webpack-dev-server only supports webpack-dev-server v3 and v4. Found: ${webpackDevServerFacts.version}.`)
+  },
+}

npm/webpack-dev-server/test-wds-3.js

@@ -0,0 +1,49 @@
+const execa = require('execa')
+const pkg = require('./package.json')
+const fs = require('fs')
+
+/**
+ * This file installs WebpackDevServer 3 and runs the tests for the dev-server.
+ * We read package.json, update the webpack version, then re-run yarn install.
+ * After it finishes, pass or fail,
+ * we revert the package.json back to the original state.
+ *
+ * The tests for the example projects (inside of examples) run with WebpackDevServer 3.
+ * This ensures we have some coverage for both versions.
+ */
+const main = async () => {
+  const originalPkg = JSON.stringify(pkg, null, 2)
+
+  const resetPkg = async () => {
+    fs.writeFileSync('package.json', originalPkg, 'utf8')
+    await execa('yarn', ['install'], { stdio: 'inherit' })
+  }
+
+  const checkExit = async ({ exitCode }) => {
+    if (typeof exitCode !== 'number') {
+      // eslint-disable-next-line no-console
+      console.error(`Finished with missing exit code from execa (received ${exitCode})`)
+    }
+
+    await resetPkg()
+    process.exit(exitCode)
+  }
+
+  pkg.devDependencies['webpack-dev-server'] = '^3.11.0'
+  // eslint-disable-next-line no-console
+  console.log('[@cypress/webpack-dev-server]: updating package.json...')
+  fs.writeFileSync('package.json', JSON.stringify(pkg, null, 2))
+
+  // eslint-disable-next-line no-console
+  console.log('[@cypress/webpack-dev-server]: install dependencies...')
+  await execa('yarn', ['install'], { stdio: 'inherit' })
+
+  const { exitCode } = await execa('yarn', ['test-all'], { stdio: 'inherit' })
+
+  await checkExit({ exitCode })
+}
+
+// execute main function if called from command line
+if (require.main === module) {
+  main()
+}

npm/webpack-dev-server/test/e2e.spec.ts

@@ -1,10 +1,10 @@
-import webpack from 'webpack'
 import path from 'path'
 import sinon from 'sinon'
 import { expect } from 'chai'
 import { EventEmitter } from 'events'
 import http from 'http'
 import fs from 'fs'
+import { webpackDevServerFacts } from '../src/webpackDevServerFacts'
 
 import { startDevServer } from '../'
 
@@ -34,11 +34,11 @@ const requestSpecFile = (port: number) => {
 
 const root = path.join(__dirname, '..')
 
-const webpackConfig: webpack.Configuration = {
-  output: {
-    path: root,
-    publicPath: root,
-  },
+const webpackConfig = {
+  devServer: webpackDevServerFacts.isV3()
+    ? { contentBase: root }
+    : { static: { directory: root } },
+
 }
 
 const specs: Cypress.Cypress['spec'][] = [

npm/webpack-dev-server/test/unit/webpackDevServerFacts.spec.ts

@@ -0,0 +1,19 @@
+import { expect } from 'chai'
+import { webpackDevServerFacts } from '../../src/webpackDevServerFacts'
+
+describe('webpackDevServerFacts', () => {
+  it('should detect v3', () => {
+    expect(webpackDevServerFacts.isV3('3.0.0')).equals(true)
+    expect(webpackDevServerFacts.isV3('3.1.4')).equals(true)
+    expect(webpackDevServerFacts.isV3('4.0.0')).equals(false)
+    expect(webpackDevServerFacts.isV3('4.3.0')).equals(false)
+  })
+
+  it('should detect v4', () => {
+    expect(webpackDevServerFacts.isV4('3.0.0')).equals(false)
+    expect(webpackDevServerFacts.isV4('3.1.4')).equals(false)
+    expect(webpackDevServerFacts.isV4('3.4.4')).equals(false)
+    expect(webpackDevServerFacts.isV4('4.0.0')).equals(true)
+    expect(webpackDevServerFacts.isV4('4.3.0')).equals(true)
+  })
+})