AttributeReader reads attributes from class traits

CHANGELOG.md

@@ -18,6 +18,8 @@ a release.
 ---
 
 ## [Unreleased]
+### Added
+- AttributeReader reads attributes from class traits
 
 ## [3.16.1]
 ### Fixed

src/Mapping/Driver/AttributeReader.php

@@ -26,7 +26,7 @@ final class AttributeReader
      */
     public function getClassAnnotations(\ReflectionClass $class): array
     {
-        return $this->convertToAttributeInstances($class->getAttributes());
+        return $this->convertToAttributeInstances($this->getClassAndTraitsAttributes($class));
     }
 
     /**
@@ -94,6 +94,24 @@ private function convertToAttributeInstances(iterable $attributes): array
         return $instances;
     }
 
+    /**
+     * Get attributes from a class including those from traits.
+     *
+     * @phpstan-param \ReflectionClass<object> $class
+     *
+     * @return \ReflectionAttribute<object>[]
+     */
+    private function getClassAndTraitsAttributes(\ReflectionClass $class): array
+    {
+        $traitAttributes = array_reduce(
+            $class->getTraits(),
+            static fn (array $carry, \ReflectionClass $trait) => array_merge($trait->getAttributes(), $carry),
+            []
+        );
+
+        return array_merge($class->getAttributes(), $traitAttributes);
+    }
+
     private function isRepeatable(string $attributeClassName): bool
     {
         if (isset($this->isRepeatableAttribute[$attributeClassName])) {