From 33ef68cf91904d6e785389e140755f9e4320afd4 Mon Sep 17 00:00:00 2001
From: Daniel Puckowski <puckowski.d@gmail.com>
Date: Mon, 1 Sep 2025 07:58:22 -0400
Subject: [PATCH] fix(issue#4354): unkown at-rule expression commas

* Fix issue #4354 unknown at-rule expressions should not have commas in
  keyword list.
---
 packages/less/src/less/parser/parser.js     | 2 +-
 packages/less/src/less/tree/atrule.js       | 6 ++++--
 packages/test-data/css/_main/tailwind.css   | 3 +++
 packages/test-data/less/_main/tailwind.less | 3 +++
 4 files changed, 11 insertions(+), 3 deletions(-)
 create mode 100644 packages/test-data/css/_main/tailwind.css
 create mode 100644 packages/test-data/less/_main/tailwind.less

diff --git a/packages/less/src/less/parser/parser.js b/packages/less/src/less/parser/parser.js
index 76676f5fe..ebc913665 100644
--- a/packages/less/src/less/parser/parser.js
+++ b/packages/less/src/less/parser/parser.js
@@ -2217,7 +2217,7 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
                     parserInput.forget();
                     return new(tree.AtRule)(name, value, rules, index + currentIndex, fileInfo,
                         context.dumpLineNumbers ? getDebugInfo(index) : null,
-                        isRooted
+                        isRooted, undefined, hasUnknown
                     );
                 }
 
diff --git a/packages/less/src/less/tree/atrule.js b/packages/less/src/less/tree/atrule.js
index df36a5d87..d6886ae58 100644
--- a/packages/less/src/less/tree/atrule.js
+++ b/packages/less/src/less/tree/atrule.js
@@ -12,7 +12,8 @@ const AtRule = function(
     currentFileInfo,
     debugInfo,
     isRooted,
-    visibilityInfo
+    visibilityInfo,
+    hasUnknown
 ) {
     let i;
     var selectors = (new Selector([], null, null, this._index, this._fileInfo)).createEmptySelectors();
@@ -62,6 +63,7 @@ const AtRule = function(
     this.isRooted = isRooted || false;
     this.copyVisibilityInfo(visibilityInfo);
     this.allowRoot = true;
+    this.hasUnknown = hasUnknown;
 }
 
 AtRule.prototype = Object.assign(new Node(), {
@@ -135,7 +137,7 @@ AtRule.prototype = Object.assign(new Node(), {
 
         if (value) {
             value = value.eval(context);
-            if (value.value && this.keywordList(value.value)) {
+            if (!this.hasUnknown && value.value && this.keywordList(value.value)) {
                 value = new Anonymous(value.value.map(keyword => keyword.value).join(', '), this.getIndex(), this.fileInfo());
             }
         }
diff --git a/packages/test-data/css/_main/tailwind.css b/packages/test-data/css/_main/tailwind.css
new file mode 100644
index 000000000..499decb21
--- /dev/null
+++ b/packages/test-data/css/_main/tailwind.css
@@ -0,0 +1,3 @@
+.box {
+  @apply h-64 w-64;
+}
diff --git a/packages/test-data/less/_main/tailwind.less b/packages/test-data/less/_main/tailwind.less
new file mode 100644
index 000000000..499decb21
--- /dev/null
+++ b/packages/test-data/less/_main/tailwind.less
@@ -0,0 +1,3 @@
+.box {
+  @apply h-64 w-64;
+}