Remove esm loader

packages/next/src/bin/next.ts

@@ -126,10 +126,7 @@ async function main() {
   const currentArgsSpec = commandArgs[command]()
   const validatedArgs = getValidatedArgs(currentArgsSpec, forwardedArgs)
 
-  if (
-    (command === 'start' || command === 'dev') &&
-    !process.env.NEXT_PRIVATE_WORKER
-  ) {
+  if (command === 'dev') {
     const dir = getProjectDir(
       process.env.NEXT_PRIVATE_DEV_DIR || validatedArgs._[0]
     )

packages/next/src/build/index.ts

@@ -147,10 +147,9 @@ import { startTypeChecking } from './type-check'
 import { generateInterceptionRoutesRewrites } from '../lib/generate-interception-routes-rewrites'
 
 import { buildDataRoute } from '../server/lib/router-utils/build-data-route'
-import { defaultOverrides } from '../server/import-overrides'
+import { defaultOverrides } from '../server/require-hook'
 import { initialize as initializeIncrementalCache } from '../server/lib/incremental-cache-server'
 import { nodeFs } from '../server/lib/node-fs-methods'
-import { getEsmLoaderPath } from '../server/lib/get-esm-loader-path'
 
 export type SsgRoute = {
   initialRevalidateSeconds: number | false
@@ -1251,11 +1250,6 @@ export default async function build(
           },
           numWorkers,
           forkOptions: {
-            execArgv: [
-              '--experimental-loader',
-              getEsmLoaderPath(),
-              '--no-warnings',
-            ],
             env: {
               ...process.env,
               __NEXT_INCREMENTAL_CACHE_IPC_PORT: incrementalCacheIpcPort + '',
@@ -2136,7 +2130,7 @@ export default async function build(
                     require.resolve('next/dist/server/lib/start-server'),
                     require.resolve('next/dist/server/next'),
                     require.resolve('next/dist/esm/server/esm-loader.mjs'),
-                    require.resolve('next/dist/server/import-overrides'),
+                    require.resolve('next/dist/server/require-hook'),
                   ]
                 : []),
               require.resolve('next/dist/server/next-server'),

packages/next/src/build/webpack-config.ts

@@ -69,7 +69,7 @@ import { NextFontManifestPlugin } from './webpack/plugins/next-font-manifest-plu
 import { getSupportedBrowsers } from './utils'
 import { MemoryWithGcCachePlugin } from './webpack/plugins/memory-with-gc-cache-plugin'
 import { getBabelConfigFile } from './get-babel-config-file'
-import { defaultOverrides } from '../server/import-overrides'
+import { defaultOverrides } from '../server/require-hook'
 
 type ExcludesFalse = <T>(x: T | false) => x is T
 type ClientEntries = {

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

@@ -17,14 +17,15 @@ import { fileExists, FileType } from '../lib/file-exists'
 import { getNpxCommand } from '../lib/helpers/get-npx-command'
 import { createSelfSignedCertificate } from '../lib/mkcert'
 import uploadTrace from '../trace/upload-trace'
-import { startServer } from '../server/lib/start-server'
-import { loadEnvConfig } from '@next/env'
+import { initialEnv, loadEnvConfig } from '@next/env'
 import { trace } from '../trace'
+import { validateTurboNextConfig } from '../lib/turbopack-warning'
+import { fork } from 'child_process'
+import { RESTART_EXIT_CODE } from '../server/lib/setup-server-worker'
 import {
   getReservedPortExplanation,
   isPortIsReserved,
 } from '../lib/helpers/get-reserved-port'
-import { validateTurboNextConfig } from '../lib/turbopack-warning'
 
 let dir: string
 let config: NextConfigComplete
@@ -231,6 +232,40 @@ const nextDev: CliCommand = async (args) => {
   setGlobal('phase', PHASE_DEVELOPMENT_SERVER)
   setGlobal('distDir', distDir)
 
+  const startServerPath = require.resolve('../server/lib/start-server')
+
+  async function startServer(options: StartServerOptions) {
+    return new Promise<void>((resolve) => {
+      let resolved = false
+
+      const child = fork(startServerPath, {
+        stdio: 'inherit',
+        env: {
+          ...((initialEnv || process.env) as typeof process.env),
+          NEXT_PRIVATE_WORKER: '1',
+        },
+      })
+
+      child.on('message', (msg: any) => {
+        if (msg && typeof msg === 'object') {
+          if (msg.nextWorkerReady) {
+            child.send({ nextWorkerOptions: options })
+          } else if (msg.nextServerReady && !resolved) {
+            resolved = true
+            resolve()
+          }
+        }
+      })
+
+      child.on('exit', async (code) => {
+        if (code === RESTART_EXIT_CODE) {
+          return startServer(options)
+        }
+        await handleSessionStop()
+      })
+    })
+  }
+
   const runDevServer = async (reboot: boolean) => {
     try {
       if (!!args['--experimental-https']) {

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

@@ -10,7 +10,7 @@ export function loadWebpackHook() {
 
   // hook the Node.js require so that webpack requires are
   // routed to the bundled and now initialized webpack version
-  require('../server/import-overrides').addHookAliases(
+  require('../server/require-hook').addHookAliases(
     [
       ['webpack', 'next/dist/compiled/webpack/webpack-lib'],
       ['webpack/package', 'next/dist/compiled/webpack/package'],

packages/next/src/server/lib/start-server.ts

@@ -358,3 +358,13 @@ export async function startServer({
     })
   }
 }
+
+if (process.env.NEXT_PRIVATE_WORKER && process.send) {
+  process.addListener('message', async (msg: any) => {
+    if (msg && typeof msg && msg.nextWorkerOptions && process.send) {
+      await startServer(msg.nextWorkerOptions)
+      process.send({ nextServerReady: true })
+    }
+  })
+  process.send({ nextWorkerReady: true })
+}

packages/next/src/server/next.ts

@@ -4,57 +4,11 @@ import type { UrlWithParsedQuery } from 'url'
 import type { NextConfigComplete } from './config-shared'
 import type { IncomingMessage, ServerResponse } from 'http'
 import type { NextUrlWithParsedQuery } from './request-meta'
-import { spawnSync } from 'child_process'
-import { getEsmLoaderPath } from './lib/get-esm-loader-path'
 import {
-  RESTART_EXIT_CODE,
   WorkerRequestHandler,
   WorkerUpgradeHandler,
 } from './lib/setup-server-worker'
 
-// if we are not inside of the esm loader enabled
-// worker we need to re-spawn with correct args
-// we can't do this if imported in jest test file otherwise
-// it duplicates tests
-if (
-  typeof jest === 'undefined' &&
-  !process.env.NEXT_PRIVATE_WORKER &&
-  (process.env.__NEXT_PRIVATE_PREBUNDLED_REACT ||
-    process.env.NODE_ENV === 'development')
-) {
-  const nodePath = process.argv0
-
-  const newArgs = [
-    '--experimental-loader',
-    getEsmLoaderPath(),
-    '--no-warnings',
-    ...process.argv.splice(1),
-  ]
-  function startWorker() {
-    try {
-      const result = spawnSync(nodePath, newArgs, {
-        stdio: 'inherit',
-        env: {
-          ...process.env,
-          NEXT_PRIVATE_WORKER: '1',
-        },
-      })
-
-      if (
-        result.status === RESTART_EXIT_CODE &&
-        process.env.NODE_ENV === 'development'
-      ) {
-        startWorker()
-      }
-      process.exit(0)
-    } catch (err) {
-      console.error(err)
-      process.exit(1)
-    }
-  }
-  startWorker()
-}
-
 import './require-hook'
 import './node-polyfill-fetch'
 import './node-polyfill-crypto'

packages/next/src/server/require-hook.js → packages/next/src/server/require-hook.ts

@@ -8,16 +8,43 @@ const mod = require('module')
 const originalRequire = mod.prototype.require
 const resolveFilename = mod._resolveFilename
 
-const { hookPropertyMap } = require('./import-overrides')
 const { PHASE_PRODUCTION_BUILD } = require('../shared/lib/constants')
 
+let resolve: typeof require.resolve = process.env.NEXT_MINIMAL
+  ? // @ts-ignore
+    __non_webpack_require__.resolve
+  : require.resolve
+
+export const hookPropertyMap = new Map()
+
+export const defaultOverrides = {
+  'styled-jsx': path.dirname(resolve('styled-jsx/package.json')),
+  'styled-jsx/style': resolve('styled-jsx/style'),
+}
+
+const toResolveMap = (map: Record<string, string>): [string, string][] =>
+  Object.entries(map).map(([key, value]) => [key, resolve(value)])
+
+export function addHookAliases(aliases: [string, string][] = []) {
+  for (const [key, value] of aliases) {
+    hookPropertyMap.set(key, value)
+  }
+}
+
+addHookAliases(toResolveMap(defaultOverrides))
+
 mod._resolveFilename = function (
-  originalResolveFilename,
-  requestMap,
-  request,
-  parent,
-  isMain,
-  options
+  originalResolveFilename: (
+    request: string,
+    parent: string,
+    isMain: boolean,
+    opts: any
+  ) => string,
+  requestMap: Map<string, string>,
+  request: string,
+  parent: string,
+  isMain: boolean,
+  options: any
 ) {
   const hookResolved = requestMap.get(request)
   if (hookResolved) request = hookResolved
@@ -30,7 +57,7 @@ mod._resolveFilename = function (
 // This is a hack to make sure that if a user requires a Next.js module that wasn't bundled
 // that needs to point to the rendering runtime version, it will point to the correct one.
 // This can happen on `pages` when a user requires a dependency that uses next/image for example.
-mod.prototype.require = function (request) {
+mod.prototype.require = function (request: string) {
   if (
     (process.env.NEXT_PHASE !== PHASE_PRODUCTION_BUILD ||
       process.env.NEXT_IS_EXPORT_WORKER) &&