From f8bad0476039dfc10bb9d2554c0b96fd2f994549 Mon Sep 17 00:00:00 2001
From: Shu Ding <g@shud.in>
Date: Wed, 7 Dec 2022 20:40:19 +0100
Subject: [PATCH 1/2] skip css dev loader for prod

---
 packages/next/build/webpack/config/blocks/css/index.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/next/build/webpack/config/blocks/css/index.ts b/packages/next/build/webpack/config/blocks/css/index.ts
index 546bcc265913708..b5509f3f8ceac9d 100644
--- a/packages/next/build/webpack/config/blocks/css/index.ts
+++ b/packages/next/build/webpack/config/blocks/css/index.ts
@@ -251,7 +251,7 @@ export const css = curry(async function css(
               ],
             })
           : null,
-        ctx.hasAppDir && !ctx.isServer
+        ctx.hasAppDir && !ctx.isServer && !ctx.isProduction
           ? markRemovable({
               sideEffects: false,
               test: regexCssModules,
@@ -293,7 +293,7 @@ export const css = curry(async function css(
               ],
             })
           : null,
-        ctx.hasAppDir && !ctx.isServer
+        ctx.hasAppDir && !ctx.isServer && !ctx.isProduction
           ? markRemovable({
               sideEffects: false,
               test: regexSassModules,
@@ -382,7 +382,7 @@ export const css = curry(async function css(
     fns.push(
       loader({
         oneOf: [
-          ctx.hasAppDir
+          ctx.hasAppDir && !ctx.isProduction
             ? markRemovable({
                 sideEffects: true,
                 test: regexCssGlobal,
@@ -394,7 +394,7 @@ export const css = curry(async function css(
                 ],
               })
             : null,
-          ctx.hasAppDir
+          ctx.hasAppDir && !ctx.isProduction
             ? markRemovable({
                 sideEffects: true,
                 test: regexSassGlobal,

From 1d0fa9eb4ad638974f0599cdf7bf347c1fa84258 Mon Sep 17 00:00:00 2001
From: Shu Ding <g@shud.in>
Date: Wed, 7 Dec 2022 20:58:30 +0100
Subject: [PATCH 2/2] fix

---
 .../build/webpack/config/blocks/css/index.ts  |  8 ++---
 .../loaders/next-flight-css-dev-loader.ts     | 31 ++++++++++++-------
 2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/packages/next/build/webpack/config/blocks/css/index.ts b/packages/next/build/webpack/config/blocks/css/index.ts
index b5509f3f8ceac9d..546bcc265913708 100644
--- a/packages/next/build/webpack/config/blocks/css/index.ts
+++ b/packages/next/build/webpack/config/blocks/css/index.ts
@@ -251,7 +251,7 @@ export const css = curry(async function css(
               ],
             })
           : null,
-        ctx.hasAppDir && !ctx.isServer && !ctx.isProduction
+        ctx.hasAppDir && !ctx.isServer
           ? markRemovable({
               sideEffects: false,
               test: regexCssModules,
@@ -293,7 +293,7 @@ export const css = curry(async function css(
               ],
             })
           : null,
-        ctx.hasAppDir && !ctx.isServer && !ctx.isProduction
+        ctx.hasAppDir && !ctx.isServer
           ? markRemovable({
               sideEffects: false,
               test: regexSassModules,
@@ -382,7 +382,7 @@ export const css = curry(async function css(
     fns.push(
       loader({
         oneOf: [
-          ctx.hasAppDir && !ctx.isProduction
+          ctx.hasAppDir
             ? markRemovable({
                 sideEffects: true,
                 test: regexCssGlobal,
@@ -394,7 +394,7 @@ export const css = curry(async function css(
                 ],
               })
             : null,
-          ctx.hasAppDir && !ctx.isProduction
+          ctx.hasAppDir
             ? markRemovable({
                 sideEffects: true,
                 test: regexSassGlobal,
diff --git a/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts b/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
index 8bfd62b9f38f189..43f994e35b423b7 100644
--- a/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
+++ b/packages/next/build/webpack/loaders/next-flight-css-dev-loader.ts
@@ -5,25 +5,32 @@
  */
 
 export function pitch(this: any) {
-  const content = this.fs.readFileSync(this.resourcePath)
-  this.data.__checksum = (
-    typeof content === 'string' ? Buffer.from(content) : content
-  ).toString('hex')
+  if (process.env.NODE_ENV !== 'production') {
+    const content = this.fs.readFileSync(this.resourcePath)
+    this.data.__checksum = (
+      typeof content === 'string' ? Buffer.from(content) : content
+    ).toString('hex')
+  }
 }
 
 const NextServerCSSLoader = function (this: any, content: string) {
   this.cacheable && this.cacheable()
 
-  const isCSSModule = this.resourcePath.match(/\.module\.(css|sass|scss)$/)
-  if (isCSSModule) {
-    return (
-      content +
-      '\nmodule.exports.__checksum = ' +
-      JSON.stringify(this.data.__checksum)
-    )
+  // Only add the checksum during development.
+  if (process.env.NODE_ENV !== 'production') {
+    const isCSSModule = this.resourcePath.match(/\.module\.(css|sass|scss)$/)
+    if (isCSSModule) {
+      return (
+        content +
+        '\nmodule.exports.__checksum = ' +
+        JSON.stringify(this.data.__checksum)
+      )
+    }
+
+    return `export default ${JSON.stringify(this.data.__checksum)}`
   }
 
-  return `export default ${JSON.stringify(this.data.__checksum)}`
+  return content
 }
 
 export default NextServerCSSLoader