Ensure Webpack isn't loaded in render workers (#52241)

There's no need to require the HotLoader module as well as Webpack in render workers, as we are not running compilation there. This reduces 10 MB memory in total and some time from `require`ing Webpack.

Before:

<img width="1639" alt="CleanShot 2023-07-05 at 11 33 39@2x" src="https://github.com/vercel/next.js/assets/3676859/48f31051-7a27-4cf6-94aa-1b2ddf313f20">

After:

<img width="1639" alt="CleanShot 2023-07-05 at 12 02 04@2x" src="https://github.com/vercel/next.js/assets/3676859/4c717d75-c0cd-458f-a6c9-6f967ae6df90">

packages/next/src/build/webpack/plugins/next-types-plugin.test.ts → packages/next/src/build/webpack/plugins/next-types-plugin/index.test.ts

@@ -1,4 +1,4 @@
-import { NextTypesPlugin } from './next-types-plugin'
+import { NextTypesPlugin } from '.'
 
 describe('next-types-plugin', () => {
   it('should generate correct base import path', () => {

packages/next/src/build/webpack/plugins/next-types-plugin.ts → packages/next/src/build/webpack/plugins/next-types-plugin/index.ts

@@ -1,19 +1,20 @@
-import type { Rewrite, Redirect } from '../../../lib/load-custom-routes'
+import type { Rewrite, Redirect } from '../../../../lib/load-custom-routes'
 import type { Token } from 'next/dist/compiled/path-to-regexp'
 
 import fs from 'fs/promises'
 import { webpack, sources } from 'next/dist/compiled/webpack/webpack'
 import { parse } from 'next/dist/compiled/path-to-regexp'
 import path from 'path'
 
-import { WEBPACK_LAYERS } from '../../../lib/constants'
-import { denormalizePagePath } from '../../../shared/lib/page-path/denormalize-page-path'
-import { ensureLeadingSlash } from '../../../shared/lib/page-path/ensure-leading-slash'
-import { normalizePathSep } from '../../../shared/lib/page-path/normalize-path-sep'
-import { HTTP_METHODS } from '../../../server/web/http'
-import { isDynamicRoute } from '../../../shared/lib/router/utils'
-import { normalizeAppPath } from '../../../shared/lib/router/utils/app-paths'
-import { getPageFromPath } from '../../entries'
+import { WEBPACK_LAYERS } from '../../../../lib/constants'
+import { denormalizePagePath } from '../../../../shared/lib/page-path/denormalize-page-path'
+import { ensureLeadingSlash } from '../../../../shared/lib/page-path/ensure-leading-slash'
+import { normalizePathSep } from '../../../../shared/lib/page-path/normalize-path-sep'
+import { HTTP_METHODS } from '../../../../server/web/http'
+import { isDynamicRoute } from '../../../../shared/lib/router/utils'
+import { normalizeAppPath } from '../../../../shared/lib/router/utils/app-paths'
+import { getPageFromPath } from '../../../entries'
+import { devPageFiles } from './shared'
 
 const PLUGIN_NAME = 'NextTypesPlugin'
 
@@ -188,8 +189,6 @@ async function collectNamedSlots(layoutPath: string) {
   return slots
 }
 
-export const devPageFiles = new Set<string>()
-
 // By exposing the static route types separately as string literals,
 // editors can provide autocompletion for them. However it's currently not
 // possible to provide the same experience for dynamic routes.

packages/next/src/build/webpack/plugins/next-types-plugin/shared.ts

@@ -0,0 +1,2 @@
+// TODO: Eliminate this singleton in the future.
+export const devPageFiles = new Set<string>()

packages/next/src/server/config.ts

@@ -747,7 +747,10 @@ export default async function loadConfig(
     : Log
 
   await loadEnvConfig(dir, phase === PHASE_DEVELOPMENT_SERVER, curLog)
-  loadWebpackHook()
+
+  if (!process.env.__NEXT_PRIVATE_RENDER_WORKER) {
+    loadWebpackHook()
+  }
 
   let configFileName = 'next.config.js'
 

packages/next/src/server/dev/next-dev-server.ts

@@ -12,6 +12,7 @@ import type { MiddlewareRoutingItem } from '../base-server'
 import type { MiddlewareMatcher } from '../../build/analysis/get-page-static-info'
 import type { FunctionComponent } from 'react'
 import type { RouteMatch } from '../future/route-matches/route-match'
+import type { default as THotReloader } from './hot-reloader'
 
 import fs from 'fs'
 import { Worker } from 'next/dist/compiled/jest-worker'
@@ -49,7 +50,6 @@ import { removePathPrefix } from '../../shared/lib/router/utils/remove-path-pref
 import { eventCliSession } from '../../telemetry/events'
 import { Telemetry } from '../../telemetry/storage'
 import { setGlobal } from '../../trace'
-import HotReloader from './hot-reloader'
 import { createValidFileMatcher, findPageFile } from '../lib/find-page-file'
 import { getNodeOptionsWithoutInspect } from '../lib/utils'
 import {
@@ -79,10 +79,9 @@ import {
   isMiddlewareFile,
   NestedMiddlewareError,
 } from '../../build/utils'
-import { getDefineEnv } from '../../build/webpack-config'
 import loadJsConfig from '../../build/load-jsconfig'
 import { formatServerError } from '../../lib/format-server-error'
-import { devPageFiles } from '../../build/webpack/plugins/next-types-plugin'
+import { devPageFiles } from '../../build/webpack/plugins/next-types-plugin/shared'
 import {
   DevRouteMatcherManager,
   RouteEnsurer,
@@ -126,7 +125,7 @@ export default class DevServer extends Server {
   private devReady: Promise<void>
   private setDevReady?: Function
   private webpackWatcher?: any | null
-  private hotReloader?: HotReloader
+  private hotReloader?: THotReloader
   private isCustomServer: boolean
   protected sortedRoutes?: string[]
   private addedUpgradeListener = false
@@ -723,6 +722,8 @@ export default class DevServer extends Server {
                   typeof plugin.definitions === 'object' &&
                   plugin.definitions.__NEXT_DEFINE_ENV
                 ) {
+                  const { getDefineEnv } =
+                    require('../../build/webpack-config') as typeof import('../../build/webpack-config')
                   const newDefine = getDefineEnv({
                     dev: true,
                     config: this.nextConfig,
@@ -900,6 +901,9 @@ export default class DevServer extends Server {
 
     // router worker does not start webpack compilers
     if (!this.isRenderWorker) {
+      const { default: HotReloader } =
+        require('./hot-reloader') as typeof import('./hot-reloader')
+
       this.hotReloader = new HotReloader(this.dir, {
         pagesDir: this.pagesDir,
         distDir: this.distDir,
@@ -911,6 +915,7 @@ export default class DevServer extends Server {
         telemetry,
       })
     }
+
     await super.prepareImpl()
     await this.addExportPathMapRoutes()
     await this.hotReloader?.start()