Fix app sc_client componet HMR server-side (vercel#41510)

This ensures we properly clear the `sc_client` component cache from
`react-server-dom-webpack` in development so that HMR works properly
after a refresh.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

Fixes: [slack
thread](https://vercel.slack.com/archives/C043ANYDB24/p1666051202574509)

packages/next/build/webpack/plugins/nextjs-require-cache-hot-reloader.ts

@@ -68,15 +68,33 @@ export class NextJsRequireCacheHotReloader implements WebpackPluginInstance {
         )
         deleteCache(runtimeChunkPath)
       })
+      let hasAppPath = false
 
       // we need to make sure to clear all server entries from cache
       // since they can have a stale webpack-runtime cache
       // which needs to always be in-sync
-      const entries = [...compilation.entries.keys()].filter(
-        (entry) =>
-          entry.toString().startsWith('pages/') ||
-          entry.toString().startsWith('app/')
-      )
+      const entries = [...compilation.entries.keys()].filter((entry) => {
+        const isAppPath = entry.toString().startsWith('app/')
+        hasAppPath = hasAppPath || isAppPath
+        return entry.toString().startsWith('pages/') || isAppPath
+      })
+
+      if (hasAppPath) {
+        // ensure we reset the cache for sc_server components
+        // loaded via react-server-dom-webpack
+        const reactWebpackModId = require.resolve(
+          'next/dist/compiled/react-server-dom-webpack'
+        )
+        const reactWebpackMod = require.cache[reactWebpackModId]
+
+        if (reactWebpackMod) {
+          for (const child of reactWebpackMod.children) {
+            child.parent = null
+            delete require.cache[child.id]
+          }
+        }
+        delete require.cache[reactWebpackModId]
+      }
 
       entries.forEach((page) => {
         const outputPath = path.join(

packages/next/server/app-render.tsx

@@ -8,7 +8,6 @@ import type { FontLoaderManifest } from '../build/webpack/plugins/font-loader-ma
 import React, { experimental_use as use } from 'react'
 
 import { ParsedUrlQuery } from 'querystring'
-import { createFromReadableStream } from 'next/dist/compiled/react-server-dom-webpack'
 import { NextParsedUrlQuery } from './request-meta'
 import RenderResult from './render-result'
 import {
@@ -271,6 +270,9 @@ function useFlightResponse(
   if (flightResponseRef.current !== null) {
     return flightResponseRef.current
   }
+  const {
+    createFromReadableStream,
+  } = require('next/dist/compiled/react-server-dom-webpack')
 
   const [renderStream, forwardStream] = readableStreamTee(req)
   const res = createFromReadableStream(renderStream, {

test/e2e/app-dir/index.test.ts

@@ -1197,6 +1197,50 @@ describe('app dir', () => {
       })
 
       if (isDev) {
+        it('should HMR correctly for client component', async () => {
+          const filePath = 'app/client-component-route/page.js'
+          const origContent = await next.readFile(filePath)
+
+          try {
+            const browser = await webdriver(next.url, '/client-component-route')
+
+            const ssrInitial = await renderViaHTTP(
+              next.url,
+              '/client-component-route'
+            )
+
+            expect(ssrInitial).toContain(
+              'hello from app/client-component-route'
+            )
+
+            expect(await browser.elementByCss('p').text()).toContain(
+              'hello from app/client-component-route'
+            )
+
+            await next.patchFile(
+              filePath,
+              origContent.replace('hello from', 'swapped from')
+            )
+
+            await check(() => browser.elementByCss('p').text(), /swapped from/)
+
+            const ssrUpdated = await renderViaHTTP(
+              next.url,
+              '/client-component-route'
+            )
+            expect(ssrUpdated).toContain('swapped from')
+
+            await next.patchFile(filePath, origContent)
+
+            await check(() => browser.elementByCss('p').text(), /hello from/)
+            expect(
+              await renderViaHTTP(next.url, '/client-component-route')
+            ).toContain('hello from')
+          } finally {
+            await next.patchFile(filePath, origContent)
+          }
+        })
+
         it('should throw an error when getServerSideProps is used', async () => {
           const pageFile =
             'app/client-with-errors/get-server-side-props/page.js'