Update to prevent re-using workers for getStaticPaths in dev mode (#11347)

packages/next/server/static-paths-worker.ts

 import { buildStaticPaths } from '../build/utils'
 import { loadComponents } from '../next-server/server/load-components'
 
-// store initial require modules so we don't clear them below
-const initialCache = new Set(Object.keys(require.cache))
+let workerWasUsed = false
 
 // we call getStaticPaths in a separate process to ensure
 // side-effects aren't relied on in dev that will break
@@ -13,14 +12,11 @@ export async function loadStaticPaths(
   pathname: string,
   serverless: boolean
 ) {
-  // we need to clear any modules manually here since the
-  // require-cache-hot-loader doesn't affect require cache here
-  // since we're in a separate process
-  Object.keys(require.cache).forEach(mod => {
-    if (!initialCache.has(mod)) {
-      delete require.cache[mod]
-    }
-  })
+  // we only want to use each worker once to prevent any invalid
+  // caches
+  if (workerWasUsed) {
+    process.exit(1)
+  }
 
   const components = await loadComponents(
     distDir,
@@ -37,5 +33,6 @@ export async function loadStaticPaths(
     )
   }
 
+  workerWasUsed = true
   return buildStaticPaths(pathname, components.getStaticPaths)
 }

test/integration/prerender/pages/blog/[post]/index.js

 import React from 'react'
 import Link from 'next/link'
 import { useRouter } from 'next/router'
+import 'firebase/firestore'
 
 export async function getStaticPaths() {
   return {

test/integration/prerender/test/index.test.js

@@ -1065,6 +1065,16 @@ describe('SSG Prerender', () => {
       await killApp(app)
     })
 
+    it('should work with firebase import and getStaticPaths', async () => {
+      const html = await renderViaHTTP(appPort, '/blog/post-1')
+      expect(html).toContain('post-1')
+      expect(html).not.toContain('Error: Failed to load')
+
+      const html2 = await renderViaHTTP(appPort, '/blog/post-1')
+      expect(html2).toContain('post-1')
+      expect(html2).not.toContain('Error: Failed to load')
+    })
+
     it('should not cache getStaticPaths errors', async () => {
       const errMsg = /The `fallback` key must be returned from getStaticPaths/
       await check(() => renderViaHTTP(appPort, '/blog/post-1'), /post-1/)
@@ -1088,7 +1098,21 @@ describe('SSG Prerender', () => {
   })
 
   describe('serverless mode', () => {
+    const blogPagePath = join(appDir, 'pages/blog/[post]/index.js')
+    let origBlogPageContent
+
     beforeAll(async () => {
+      // remove firebase import since it breaks in legacy serverless mode
+      origBlogPageContent = await fs.readFile(blogPagePath, 'utf8')
+
+      await fs.writeFile(
+        blogPagePath,
+        origBlogPageContent.replace(
+          `import 'firebase/firestore'`,
+          `// import 'firebase/firestore'`
+        )
+      )
+
       await fs.writeFile(
         nextConfig,
         `module.exports = { target: 'serverless' }`,
@@ -1106,7 +1130,10 @@ describe('SSG Prerender', () => {
       distPagesDir = join(appDir, '.next/serverless/pages')
       buildId = await fs.readFile(join(appDir, '.next/BUILD_ID'), 'utf8')
     })
-    afterAll(() => killApp(app))
+    afterAll(async () => {
+      await fs.writeFile(blogPagePath, origBlogPageContent)
+      await killApp(app)
+    })
 
     it('renders data correctly', async () => {
       const port = await findPort()