Disable worker_threads by default for firebase compatibility

packages/next/build/index.ts

@@ -337,7 +337,7 @@ export default async function build(dir: string, conf = null): Promise<void> {
 
   const staticCheckWorkers = new Worker(staticCheckWorker, {
     numWorkers: config.experimental.cpus,
-    enableWorkerThreads: true,
+    enableWorkerThreads: config.experimental.workerThreads,
   })
 
   const analysisBegin = process.hrtime()
@@ -471,6 +471,7 @@ export default async function build(dir: string, conf = null): Promise<void> {
       sprPages,
       silent: true,
       buildExport: true,
+      threads: config.experimental.cpus,
       pages: combinedPages,
       outdir: path.join(distDir, 'export'),
     }

packages/next/build/webpack-config.ts

@@ -171,11 +171,12 @@ export default async function getBaseWebpackConfig(
   const webpackMode = dev ? 'development' : 'production'
 
   const terserPluginConfig = {
-    parallel: true,
-    sourceMap: false,
     cache: true,
     cpus: config.experimental.cpus,
     distDir: distDir,
+    parallel: true,
+    sourceMap: false,
+    workerThreads: config.experimental.workerThreads,
   }
   const terserOptions = {
     parse: {

packages/next/build/webpack/plugins/terser-webpack-plugin/src/TaskRunner.js

@@ -10,13 +10,14 @@ const writeFileP = promisify(writeFile)
 const readFileP = promisify(readFile)
 
 export default class TaskRunner {
-  constructor({ distDir, cpus, cache }) {
+  constructor({ distDir, cpus, cache, workerThreads }) {
     if (cache) {
       mkdirp.sync((this.cacheDir = join(distDir, 'cache', 'next-minifier')))
     }
     // In some cases cpus() returns undefined
     // https://github.com/nodejs/node/issues/19022
     this.maxConcurrentWorkers = cpus
+    this.useWorkerThreads = workerThreads
   }
 
   run(tasks, callback) {
@@ -28,7 +29,7 @@ export default class TaskRunner {
 
     if (this.maxConcurrentWorkers > 1) {
       this.workers = new Worker(worker, {
-        enableWorkerThreads: true,
+        enableWorkerThreads: this.useWorkerThreads,
         numWorkers: this.maxConcurrentWorkers,
       })
       this.boundWorkers = options => this.workers.default(options)

packages/next/build/webpack/plugins/terser-webpack-plugin/src/index.js

@@ -21,10 +21,12 @@ export class TerserPlugin {
       cache = false,
       cpus,
       distDir,
+      workerThreads,
     } = options
 
     this.cpus = cpus
     this.distDir = distDir
+    this.workerThreads = workerThreads
     this.options = {
       warningsFilter,
       sourceMap,
@@ -134,6 +136,7 @@ export class TerserPlugin {
         distDir: this.distDir,
         cpus: this.cpus,
         cache: this.options.cache,
+        workerThreads: this.workerThreads,
       })
 
       const processedAssets = new WeakSet()

packages/next/export/index.ts

@@ -267,7 +267,7 @@ export default async function(
     {
       maxRetries: 0,
       numWorkers: threads,
-      enableWorkerThreads: true,
+      enableWorkerThreads: nextConfig.experimental.workerThreads,
       exposedMethods: ['default'],
     }
   ) as any

packages/next/next-server/server/config.ts

@@ -48,6 +48,7 @@ const defaultConfig: { [key: string]: any } = {
     publicDirectory: false,
     sprFlushToDisk: true,
     deferScripts: false,
+    workerThreads: false,
   },
   future: {
     excludeDefaultMomentLocales: false,

test/integration/firebase-grpc/pages/page-1.js

@@ -0,0 +1,2 @@
+import 'firebase/firestore'
+export default () => <div>Firebase</div>

test/integration/firebase-grpc/pages/page-2.js

@@ -0,0 +1,2 @@
+import 'firebase/firestore'
+export default () => <div>Firebase</div>

test/integration/firebase-grpc/test/index.test.js

@@ -0,0 +1,33 @@
+/* eslint-env jest */
+/* global jasmine */
+import path from 'path'
+import fs from 'fs-extra'
+import { nextBuild } from 'next-test-utils'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 1
+const appDir = path.join(__dirname, '..')
+const nextConfig = path.join(appDir, 'next.config.js')
+
+describe('Building Firebase', () => {
+  // TODO: investigate re-enabling this test in node 12 environment
+  xit('Throws an error when building with firebase dependency with worker_threads', async () => {
+    await fs.writeFile(
+      nextConfig,
+      `module.exports = { experimental: { workerThreads: true } }`
+    )
+    const results = await nextBuild(appDir, [], { stdout: true, stderr: true })
+    expect(results.stdout + results.stderr).toMatch(/Build error occurred/)
+    expect(results.stdout + results.stderr).toMatch(
+      /grpc_node\.node\. Module did not self-register\./
+    )
+  })
+
+  it('Throws no error when building with firebase dependency without worker_threads', async () => {
+    await fs.remove(nextConfig)
+    const results = await nextBuild(appDir, [], { stdout: true, stderr: true })
+    expect(results.stdout + results.stderr).not.toMatch(/Build error occurred/)
+    expect(results.stdout + results.stderr).not.toMatch(
+      /grpc_node\.node\. Module did not self-register\./
+    )
+  })
+})