From d9f80ba12827bdeba18e0dabd7a7788583193e8a Mon Sep 17 00:00:00 2001
From: Adam Wathan <4323180+adamwathan@users.noreply.github.com>
Date: Thu, 7 Mar 2024 21:31:57 -0500
Subject: [PATCH 1/2] Don't crash on @apply with extra whitespace

---
 packages/tailwindcss/src/index.test.ts | 16 ++++++++++++++++
 packages/tailwindcss/src/index.ts      |  1 +
 2 files changed, 17 insertions(+)

diff --git a/packages/tailwindcss/src/index.test.ts b/packages/tailwindcss/src/index.test.ts
index 521841cbe5ce..cf7025102e5b 100644
--- a/packages/tailwindcss/src/index.test.ts
+++ b/packages/tailwindcss/src/index.test.ts
@@ -288,6 +288,22 @@ describe('@apply', () => {
       `[Error: Cannot apply unknown utility class: hocus:bg-red-500]`,
     )
   })
+
+  it('should not error with trailing whitespace', () => {
+    expect(
+      compileCss(`
+        @tailwind utilities;
+
+        .foo {
+          @apply flex ;
+        }
+      `),
+    ).toMatchInlineSnapshot(`
+      ".foo {
+        display: flex;
+      }"
+    `)
+  })
 })
 
 describe('arbitrary variants', () => {
diff --git a/packages/tailwindcss/src/index.ts b/packages/tailwindcss/src/index.ts
index 59fe7a21c870..d066a5a1f335 100644
--- a/packages/tailwindcss/src/index.ts
+++ b/packages/tailwindcss/src/index.ts
@@ -115,6 +115,7 @@ export function compile(css: string, rawCandidates: string[]) {
       if (node.kind === 'rule' && node.selector[0] === '@' && node.selector.startsWith('@apply')) {
         let candidates = node.selector
           .slice(7 /* Ignore `@apply ` when parsing the selector */)
+          .trim()
           .split(/\s+/g)
 
         // Replace the `@apply` rule with the actual utility classes

From dff173b67a349a9fef04e35ba0340d1e6124dd59 Mon Sep 17 00:00:00 2001
From: Adam Wathan <4323180+adamwathan@users.noreply.github.com>
Date: Thu, 7 Mar 2024 21:48:37 -0500
Subject: [PATCH 2/2] Update changelog

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c67efe3e85ab..745f31cf2135 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Don't error on `@apply` with leading/trailing whitespace ([#13144](https://github.com/tailwindlabs/tailwindcss/pull/13144))
+
 ## [4.0.0-alpha.6] - 2024-03-07
 
 ### Fixed