From 4518c1ec21dd777f408e1992eb9943a11ffab1d3 Mon Sep 17 00:00:00 2001
From: JJ Kasper <jj@jjsweb.site>
Date: Fri, 1 Mar 2024 16:40:39 -0800
Subject: [PATCH] Reduce memory/cache overhead from over loader processing
 #62005

---
 packages/next/src/build/webpack-config.ts     |  3 +-
 .../build/webpack/loaders/next-swc-loader.ts  | 45 +++++++++++++++++++
 .../terser-webpack-plugin/src/index.ts        | 10 -----
 3 files changed, 47 insertions(+), 11 deletions(-)

diff --git a/packages/next/src/build/webpack-config.ts b/packages/next/src/build/webpack-config.ts
index 4c0b906cc50cb..de209961f1a1d 100644
--- a/packages/next/src/build/webpack-config.ts
+++ b/packages/next/src/build/webpack-config.ts
@@ -103,7 +103,7 @@ if (parseInt(React.version) < 18) {
   throw new Error('Next.js requires react >= 18.2.0 to be installed.')
 }
 
-const babelIncludeRegexes: RegExp[] = [
+export const babelIncludeRegexes: RegExp[] = [
   /next[\\/]dist[\\/](esm[\\/])?shared[\\/]lib/,
   /next[\\/]dist[\\/](esm[\\/])?client/,
   /next[\\/]dist[\\/](esm[\\/])?pages/,
@@ -455,6 +455,7 @@ export default async function getBaseWebpackConfig(
         jsConfig,
         supportedBrowsers,
         swcCacheDir: path.join(dir, config?.distDir ?? '.next', 'cache', 'swc'),
+        transpilePackages: config.transpilePackages,
         ...extraOptions,
       } satisfies SWCLoaderOptions,
     }
diff --git a/packages/next/src/build/webpack/loaders/next-swc-loader.ts b/packages/next/src/build/webpack/loaders/next-swc-loader.ts
index b1650fa4b8334..6ca51b575dcd0 100644
--- a/packages/next/src/build/webpack/loaders/next-swc-loader.ts
+++ b/packages/next/src/build/webpack/loaders/next-swc-loader.ts
@@ -31,6 +31,22 @@ import type { WebpackLayerName } from '../../../lib/constants'
 import { isWasm, transform } from '../../swc'
 import { getLoaderSWCOptions } from '../../swc/options'
 import path, { isAbsolute } from 'path'
+import { babelIncludeRegexes } from '../../webpack-config'
+import { isResourceInPackages } from '../../handle-externals'
+
+const maybeExclude = (
+  excludePath: string,
+  transpilePackages: string[]
+): boolean => {
+  if (babelIncludeRegexes.some((r) => r.test(excludePath))) {
+    return false
+  }
+
+  const shouldBeBundled = isResourceInPackages(excludePath, transpilePackages)
+  if (shouldBeBundled) return false
+
+  return excludePath.includes('node_modules')
+}
 
 export interface SWCLoaderOptions {
   rootDir: string
@@ -46,8 +62,14 @@ export interface SWCLoaderOptions {
   serverComponents?: boolean
   bundleLayer?: WebpackLayerName
   esm?: boolean
+  transpilePackages?: string[]
 }
 
+// these are exact code conditions checked
+// for to force transpiling a `node_module`
+const FORCE_TRANSPILE_CONDITIONS =
+  /(next\/font|next\/dynamic|use server|use client)/
+
 async function loaderTransform(
   this: any,
   parentTrace: any,
@@ -58,6 +80,20 @@ async function loaderTransform(
   const filename = this.resourcePath
 
   let loaderOptions: SWCLoaderOptions = this.getOptions() || {}
+  const shouldMaybeExclude = maybeExclude(
+    filename,
+    loaderOptions.transpilePackages || []
+  )
+
+  if (shouldMaybeExclude) {
+    if (!source) {
+      throw new Error(`Invariant might be excluded but missing source`)
+    }
+
+    if (!FORCE_TRANSPILE_CONDITIONS.test(source)) {
+      return [source, inputSourceMap]
+    }
+  }
 
   const {
     isServer,
@@ -150,8 +186,17 @@ const EXCLUDED_PATHS =
 
 export function pitch(this: any) {
   const callback = this.async()
+  let loaderOptions: SWCLoaderOptions = this.getOptions() || {}
+
+  const shouldMaybeExclude = maybeExclude(
+    this.resourcePath,
+    loaderOptions.transpilePackages || []
+  )
+
   ;(async () => {
     if (
+      // if it might be excluded/no-op we can't use pitch loader
+      !shouldMaybeExclude &&
       // TODO: investigate swc file reading in PnP mode?
       !process.versions.pnp &&
       !EXCLUDED_PATHS.test(this.resourcePath) &&
diff --git a/packages/next/src/build/webpack/plugins/terser-webpack-plugin/src/index.ts b/packages/next/src/build/webpack/plugins/terser-webpack-plugin/src/index.ts
index 5112b9cc503e7..96f847c2a94c4 100644
--- a/packages/next/src/build/webpack/plugins/terser-webpack-plugin/src/index.ts
+++ b/packages/next/src/build/webpack/plugins/terser-webpack-plugin/src/index.ts
@@ -98,16 +98,6 @@ export class TerserPlugin {
               return false
             }
 
-            // don't minify _middleware as it can break in some cases
-            // and doesn't provide too much of a benefit as it's server-side
-            if (
-              name.match(
-                /(edge-runtime-webpack\.js|edge-chunks|middleware\.js$)/
-              )
-            ) {
-              return false
-            }
-
             const { info } = res
 
             // Skip double minimize assets from child compilation