Fix Web Workers with Fast Refresh

package.json

@@ -122,7 +122,8 @@
     "tree-kill": "1.2.1",
     "typescript": "3.8.3",
     "wait-port": "0.2.2",
-    "webpack-bundle-analyzer": "3.6.1"
+    "webpack-bundle-analyzer": "3.6.1",
+    "worker-loader": "2.0.0"
   },
   "resolutions": {
     "browserslist": "^4.8.3",

packages/react-refresh-utils/ReactRefreshWebpackPlugin.ts

@@ -6,8 +6,31 @@ import {
   // @ts-ignore exists in webpack 5
   RuntimeGlobals,
   version,
+  compilation as Compilation,
 } from 'webpack'
 
+// Shared between webpack 4 and 5:
+function injectRefreshFunctions(compilation: Compilation.Compilation) {
+  const hookVars: typeof compilation['mainTemplate']['hooks']['requireExtensions'] = (compilation
+    .mainTemplate.hooks as any).localVars
+
+  hookVars.tap('ReactFreshWebpackPlugin', (source) =>
+    Template.asString([
+      source,
+      '',
+      '// noop fns to prevent runtime errors during initialization',
+      'if (typeof self !== "undefined") {',
+      Template.indent('self.$RefreshReg$ = function () {};'),
+      Template.indent('self.$RefreshSig$ = function () {'),
+      Template.indent(Template.indent('return function (type) {')),
+      Template.indent(Template.indent(Template.indent('return type;'))),
+      Template.indent(Template.indent('};')),
+      Template.indent('};'),
+      '}',
+    ])
+  )
+}
+
 function webpack4(compiler: Compiler) {
   // Webpack 4 does not have a method to handle interception of module
   // execution.
@@ -16,6 +39,8 @@ function webpack4(compiler: Compiler) {
   // https://github.com/webpack/webpack/blob/4c644bf1f7cb067c748a52614500e0e2182b2700/lib/MainTemplate.js#L200
 
   compiler.hooks.compilation.tap('ReactFreshWebpackPlugin', (compilation) => {
+    injectRefreshFunctions(compilation)
+
     const hookRequire: typeof compilation['mainTemplate']['hooks']['requireExtensions'] = (compilation
       .mainTemplate.hooks as any).require
 
@@ -106,6 +131,8 @@ function webpack5(compiler: Compiler) {
   }
 
   compiler.hooks.compilation.tap('ReactFreshWebpackPlugin', (compilation) => {
+    injectRefreshFunctions(compilation)
+
     // @ts-ignore Exists in webpack 5
     compilation.hooks.additionalTreeRuntimeRequirements.tap(
       'ReactFreshWebpackPlugin',

packages/react-refresh-utils/runtime.ts

@@ -13,14 +13,6 @@ declare const self: Window & RefreshRuntimeGlobals
 // Hook into ReactDOM initialization
 RefreshRuntime.injectIntoGlobalHook(self)
 
-// noop fns to prevent runtime errors during initialization
-self.$RefreshReg$ = function () {}
-self.$RefreshSig$ = function () {
-  return function (type) {
-    return type
-  }
-}
-
 // Register global helpers
 self.$RefreshHelpers$ = RefreshHelpers
 

test/integration/worker-loader/lib/demo.worker.js

@@ -0,0 +1,4 @@
+const { Expensive } = require('./sharedCode')
+
+Expensive()
+self.postMessage(true)

test/integration/worker-loader/lib/sharedCode.js

@@ -0,0 +1,17 @@
+export function Expensive() {
+  const start = performance.now()
+  let i = 99999
+
+  const bigArray = []
+  while (--i) {
+    bigArray.push(i)
+  }
+
+  const endTime = performance.now()
+
+  if (typeof window === 'undefined') {
+    console.log('[WORKER] Completed expensive function in', endTime - start)
+  } else {
+    console.log('[WEB] Completed expensive function in', endTime - start)
+  }
+}

test/integration/worker-loader/next.config.js

@@ -0,0 +1,18 @@
+module.exports = {
+  webpack: (config, { isServer }) => {
+    config.module.rules.unshift({
+      test: /\.worker\.(js|ts|tsx)$/,
+      loader: 'worker-loader',
+      options: {
+        name: 'static/[hash].worker.js',
+        publicPath: '/_next/',
+      },
+    })
+
+    if (!isServer) {
+      config.output.globalObject = 'self'
+    }
+
+    return config
+  },
+}

test/integration/worker-loader/pages/index.js

@@ -0,0 +1,39 @@
+import * as React from 'react'
+import DemoWorker from '../lib/demo.worker'
+import { Expensive } from '../lib/sharedCode'
+
+export default function Home() {
+  const [expensiveWebStatus, setExpensiveWebStatus] = React.useState('WAIT')
+  const [expensiveWorkerStatus, setExpensiveWorkerComplete] = React.useState(
+    'WAIT'
+  )
+  const worker = React.useRef()
+
+  React.useEffect(() => {
+    worker.current = new DemoWorker()
+    worker.current.addEventListener('message', ({ data }) => {
+      if (data) {
+        setExpensiveWorkerComplete('PASS')
+      }
+    })
+    worker.current.addEventListener('error', (data) => {
+      setExpensiveWorkerComplete('FAIL')
+    })
+  }, [worker, setExpensiveWorkerComplete])
+  React.useEffect(() => {
+    try {
+      Expensive()
+      setExpensiveWebStatus('PASS')
+    } catch {
+      setExpensiveWebStatus('FAIL')
+    }
+  }, [])
+
+  return (
+    <main>
+      <h1>$RefreshRegistry repro</h1>
+      <div id="web-status">Web: {expensiveWebStatus}</div>
+      <div id="worker-status">Worker: {expensiveWorkerStatus}</div>
+    </main>
+  )
+}

test/integration/worker-loader/test/index.test.js

@@ -0,0 +1,35 @@
+/* eslint-env jest */
+
+import { check, findPort, killApp, launchApp } from 'next-test-utils'
+import webdriver from 'next-webdriver'
+import { join } from 'path'
+
+const appDir = join(__dirname, '../')
+const context = {}
+
+jest.setTimeout(1000 * 60 * 2)
+
+describe('Web Workers with Fast Refresh', () => {
+  beforeAll(async () => {
+    context.appPort = await findPort()
+    context.server = await launchApp(appDir, context.appPort)
+  })
+  afterAll(() => {
+    killApp(context.server)
+  })
+
+  it('should pass on both client and worker', async () => {
+    let browser
+    try {
+      browser = await webdriver(context.appPort, '/')
+      await browser.waitForElementByCss('#web-status')
+      await check(() => browser.elementByCss('#web-status').text(), /PASS/i)
+      await browser.waitForElementByCss('#worker-status')
+      await check(() => browser.elementByCss('#worker-status').text(), /PASS/i)
+    } finally {
+      if (browser) {
+        await browser.close()
+      }
+    }
+  })
+})

yarn.lock

@@ -9853,7 +9853,7 @@ loader-utils@2.0.0, loader-utils@^2.0.0:
     emojis-list "^3.0.0"
     json5 "^2.1.2"
 
-loader-utils@^1.4.0:
+loader-utils@^1.0.0, loader-utils@^1.4.0:
   version "1.4.0"
   resolved "https://registry.yarnpkg.com/loader-utils/-/loader-utils-1.4.0.tgz#c579b5e34cb34b1a74edc6c1fb36bfa371d5a613"
   dependencies:
@@ -14193,6 +14193,14 @@ schema-utils@2.6.6, schema-utils@^2.0.0, schema-utils@^2.6.1, schema-utils@^2.6.
     ajv "^6.12.0"
     ajv-keywords "^3.4.1"
 
+schema-utils@^0.4.0:
+  version "0.4.7"
+  resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-0.4.7.tgz#ba74f597d2be2ea880131746ee17d0a093c68187"
+  integrity sha512-v/iwU6wvwGK8HbU9yi3/nhGzP0yGSuhQMzL6ySiec1FSrZZDkhm4noOSWzrNFo/jEc+SJY6jRTwuwbSXJPDUnQ==
+  dependencies:
+    ajv "^6.1.0"
+    ajv-keywords "^3.1.0"
+
 schema-utils@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-1.0.0.tgz#0b79a93204d7b600d4b2850d1f66c2a34951c770"
@@ -16244,6 +16252,14 @@ worker-farm@^1.7.0:
   dependencies:
     errno "~0.1.7"
 
+worker-loader@2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/worker-loader/-/worker-loader-2.0.0.tgz#45fda3ef76aca815771a89107399ee4119b430ac"
+  integrity sha512-tnvNp4K3KQOpfRnD20m8xltE3eWh89Ye+5oj7wXEEHKac1P4oZ6p9oTj8/8ExqoSBnk9nu5Pr4nKfQ1hn2APJw==
+  dependencies:
+    loader-utils "^1.0.0"
+    schema-utils "^0.4.0"
+
 wrap-ansi@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/wrap-ansi/-/wrap-ansi-2.1.0.tgz#d8fc3d284dd05794fe84973caecdd1cf824fdd85"