Allow class names with 'admin__' prefix

Author: fredden

Magento2/Sniffs/Less/ClassNamingSniff.php

@@ -66,7 +66,10 @@ public function process(File $phpcsFile, $stackPtr)
                 [implode("", $matches[0])]
             );
         }
-        if (strpos($className, self::STRING_HELPER_CLASSES_PREFIX, 2) !== false) {
+
+        if (strpos($className, self::STRING_HELPER_CLASSES_PREFIX, 2) !== false
+            && !str_starts_with($className, 'admin__')
+        ) {
             $phpcsFile->addError(
                 'CSS class names should be separated with "-" (dash) instead of "_" (underscore)',
                 $stackPtr,

Magento2/Tests/Less/ClassNamingUnitTest.less

@@ -30,3 +30,8 @@
 .category-title {
   background: green;
 }
+
+// @see https://github.com/magento/magento-coding-standard/issues/409
+.admin__allowed {
+  background: green;
+}

composer.json

@@ -14,7 +14,8 @@
         "ext-dom": "*",
         "phpcompatibility/php-compatibility": "^9.3",
         "squizlabs/php_codesniffer": "^3.6.1",
-        "rector/rector": "^0.14.8"
+        "rector/rector": "^0.14.8",
+        "symfony/polyfill": "^1.16"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.5.8"