Fix memory leak in ExceptionWrapper

Author: mvorisek

src/Framework/ExceptionWrapper.php

@@ -9,11 +9,13 @@
  */
 namespace PHPUnit\Framework;
 
+use const PHP_VERSION_ID;
 use function array_keys;
 use function get_class;
 use function spl_object_hash;
 use PHPUnit\Util\Filter;
 use Throwable;
+use WeakReference;
 
 /**
  * Wraps Exceptions thrown by code under test.
@@ -38,6 +40,11 @@ final class ExceptionWrapper extends Exception
      */
     protected $previous;
 
+    /**
+     * @var null|WeakReference<Throwable>
+     */
+    private $originalException;
+
     public function __construct(Throwable $t)
     {
         // PDOException::getCode() is a string.
@@ -109,14 +116,23 @@ public function getOriginalException(): ?Throwable
      */
     private function originalException(Throwable $exceptionToStore = null): ?Throwable
     {
-        static $originalExceptions;
+        // drop once PHP 7.3 support is removed
+        if (PHP_VERSION_ID < 70400) {
+            static $originalExceptions;
 
-        $instanceId = spl_object_hash($this);
+            $instanceId = spl_object_hash($this);
+
+            if ($exceptionToStore) {
+                $originalExceptions[$instanceId] = $exceptionToStore;
+            }
+
+            return $originalExceptions[$instanceId] ?? null;
+        }
 
         if ($exceptionToStore) {
-            $originalExceptions[$instanceId] = $exceptionToStore;
+            $this->originalException = WeakReference::create($exceptionToStore);
         }
 
-        return $originalExceptions[$instanceId] ?? null;
+        return $this->originalException !== null ? $this->originalException->get() : null;
     }
 }