fix: Remove remaining rspack plugin files and fix TypeScript errors

- Delete rspack-flight-client-entry-plugin.ts and rspack-profiling-plugin.ts
- Remove imports and simplify FlightClientEntryPlugin selection
- Remove rspack compilation spans logic
- Fix MiniCssExtractPlugin loader property access with any cast

Build verified locally with pnpm --filter next run build

Author: celicoo

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

@@ -50,7 +50,6 @@ import { regexLikeCss } from './webpack/config/blocks/css'
 import { CopyFilePlugin } from './webpack/plugins/copy-file-plugin'
 import { ClientReferenceManifestPlugin } from './webpack/plugins/flight-manifest-plugin'
 import { FlightClientEntryPlugin as NextFlightClientEntryPlugin } from './webpack/plugins/flight-client-entry-plugin'
-import { RspackFlightClientEntryPlugin } from './webpack/plugins/rspack-flight-client-entry-plugin'
 import { NextTypesPlugin } from './webpack/plugins/next-types-plugin'
 import type {
   Feature,
@@ -370,10 +369,7 @@ export default async function getBaseWebpackConfig(
 
   const isRspack = Boolean(process.env.NEXT_RSPACK)
 
-  const FlightClientEntryPlugin =
-    isRspack && process.env.BUILTIN_FLIGHT_CLIENT_ENTRY_PLUGIN
-      ? RspackFlightClientEntryPlugin
-      : NextFlightClientEntryPlugin
+  const FlightClientEntryPlugin = NextFlightClientEntryPlugin
 
   // If the current compilation is aimed at server-side code instead of client-side code.
   const isNodeOrEdgeCompilation = isNodeServer || isEdgeServer

packages/next/src/build/webpack/config/blocks/css/loaders/client.ts

@@ -41,12 +41,12 @@ export function getClientStyleLoader({
     }
   }
 
-  const MiniCssExtractPlugin = (
+  const NextMiniCssExtractPlugin = (
     require('../../../../plugins/mini-css-extract-plugin') as typeof import('../../../../plugins/mini-css-extract-plugin')
   ).default
 
   return {
-    loader: MiniCssExtractPlugin.loader,
+    loader: (NextMiniCssExtractPlugin as any).loader,
     options: {
       publicPath: `${assetPrefix}/_next/`,
       esModule: false,

packages/next/src/build/webpack/plugins/rspack-flight-client-entry-plugin.ts

@@ -10,7 +10,6 @@ import type {
 import type { ModuleGraphConnection } from 'webpack'
 import { getAppLoader } from '../entries'
 import { spans as webpackCompilationSpans } from './plugins/profiling-plugin'
-import { compilationSpans as rspackCompilationSpans } from './plugins/rspack-profiling-plugin'
 import type { Span } from '../../trace'
 
 export function traverseModules(
@@ -122,9 +121,5 @@ export function getModuleReferencesInOrder(
 export function getCompilationSpan(
   compilation: Compiler | Compilation
 ): Span | undefined {
-  const compilationSpans = process.env.NEXT_RSPACK
-    ? rspackCompilationSpans
-    : webpackCompilationSpans
-
-  return compilationSpans.get(compilation)
+  return webpackCompilationSpans.get(compilation)
 }