[BUGFIX] Allow comma in quoted string in selector

CHANGELOG.md

@@ -110,6 +110,7 @@ Please also have a look at our
 
 ### Fixed
 
+- Parse quoted attribute selector value containing comma (#1323)
 - Allow comma in selectors (e.g. `:not(html, body)`) (#1293)
 - Insert `Rule` before sibling even with different property name
   (in `RuleSet::addRule()`) (#1270)

src/RuleSet/DeclarationBlock.php

@@ -40,13 +40,18 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
         $comments = [];
         $result = new DeclarationBlock($parserState->currentLine());
         try {
+            $selectors = [];
             $selectorParts = [];
             $stringWrapperCharacter = null;
-            static $stopCharacters = ['{', '}', '\'', '"'];
+            $consumedNextCharacter = false;
+            static $stopCharacters = ['{', '}', '\'', '"', ','];
             do {
-                $selectorParts[] = $parserState->consume(1)
-                    . $parserState->consumeUntil($stopCharacters, false, false, $comments);
+                if (!$consumedNextCharacter) {
+                    $selectorParts[] = $parserState->consume(1);
+                }
+                $selectorParts[] = $parserState->consumeUntil($stopCharacters, false, false, $comments);
                 $nextCharacter = $parserState->peek();
+                $consumedNextCharacter = false;
                 switch ($nextCharacter) {
                     case '\'':
                         // The fallthrough is intentional.
@@ -59,9 +64,18 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
                             }
                         }
                         break;
+                    case ',':
+                        if (!\is_string($stringWrapperCharacter)) {
+                            $selectors[] = \implode('', $selectorParts);
+                            $selectorParts = [];
+                            $parserState->consume(1);
+                            $consumedNextCharacter = true;
+                        }
+                        break;
                 }
             } while (!\in_array($nextCharacter, ['{', '}'], true) || \is_string($stringWrapperCharacter));
-            $result->setSelectors(\implode('', $selectorParts), $list);
+            $selectors[] = \implode('', $selectorParts); // add final or only selector
+            $result->setSelectors($selectors, $list);
             if ($parserState->comes('{')) {
                 $parserState->consume(1);
             }

tests/Unit/RuleSet/DeclarationBlockTest.php

@@ -68,8 +68,8 @@ public static function provideSelector(): array
             'type & pseudo-class' => ['a:hover'],
             '`not`' => [':not(#your-mug)'],
             'pseudo-element' => ['::before'],
-            'attribute with `"`' => ['[alt="{}()[]\\"\'"]'],
-            'attribute with `\'`' => ['[alt=\'{}()[]"\\\'\']'],
+            'attribute with `"`' => ['[alt="{}()[]\\"\',"]'],
+            'attribute with `\'`' => ['[alt=\'{}()[]"\\\',\']'],
         ];
     }