From 0d8073016bf214439d566fbf306e526780da11e9 Mon Sep 17 00:00:00 2001
From: Hannah Okwelum <hokwelum@wikimedia.org>
Date: Tue, 6 Aug 2024 15:25:41 +0100
Subject: [PATCH] Fix parse error when opacity is set to zero to alpha()
 function

Bug was as a result of matchReg returning "0" (zero string) when
opacity is set to zero. PHP sees this as false and ends up throwing
a Less_Exception_Parser.

Bug: T371606
Change-Id: I75704789eac249e48336898730a573ed1cddafef
---
 lib/Less/Parser.php                                       | 2 +-
 test/Fixtures/less.php/css/T371606-alpha-zero-error.css   | 3 +++
 test/Fixtures/less.php/less/T371606-alpha-zero-error.less | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 test/Fixtures/less.php/css/T371606-alpha-zero-error.css
 create mode 100644 test/Fixtures/less.php/less/T371606-alpha-zero-error.less

diff --git a/lib/Less/Parser.php b/lib/Less/Parser.php
index ef8a8164..c788e153 100644
--- a/lib/Less/Parser.php
+++ b/lib/Less/Parser.php
@@ -2134,7 +2134,7 @@ private function parseAlpha() {
 		}
 
 		$value = $this->matchReg( '/\\G[0-9]+/' );
-		if ( !$value ) {
+		if ( $value === null ) {
 			$value = $this->expect( 'parseEntitiesVariable', 'Could not parse alpha' );
 		}
 
diff --git a/test/Fixtures/less.php/css/T371606-alpha-zero-error.css b/test/Fixtures/less.php/css/T371606-alpha-zero-error.css
new file mode 100644
index 00000000..5656bcf7
--- /dev/null
+++ b/test/Fixtures/less.php/css/T371606-alpha-zero-error.css
@@ -0,0 +1,3 @@
+.alpha {
+  filter: alpha(opacity=0);
+}
diff --git a/test/Fixtures/less.php/less/T371606-alpha-zero-error.less b/test/Fixtures/less.php/less/T371606-alpha-zero-error.less
new file mode 100644
index 00000000..0c7fd30d
--- /dev/null
+++ b/test/Fixtures/less.php/less/T371606-alpha-zero-error.less
@@ -0,0 +1,3 @@
+.alpha {
+	filter: alpha(opacity=0);
+  }