bug #26568 [Debug] Reset previous exception handler earlier to prevent infinite loop (nicolas-grekas)

This PR was merged into the 2.7 branch.

Discussion
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[Debug] Reset previous exception handler earlier to prevent infinite loop

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #26438
| License       | MIT
| Doc PR        | -

Commits
-------

f7e1bb0 [Debug] Reset previous exception handler ealier to prevent infinite loop

Author: nicolas-grekas

src/Symfony/Component/Debug/ErrorHandler.php

@@ -544,15 +544,16 @@ public function handleException($exception, array $error = null)
                 }
             }
         }
+        $exceptionHandler = $this->exceptionHandler;
+        $this->exceptionHandler = null;
         try {
-            if (null !== $this->exceptionHandler) {
-                return \call_user_func($this->exceptionHandler, $exception);
+            if (null !== $exceptionHandler) {
+                return \call_user_func($exceptionHandler, $exception);
             }
             $handlerException = $handlerException ?: $exception;
         } catch (\Exception $handlerException) {
         } catch (\Throwable $handlerException) {
         }
-        $this->exceptionHandler = null;
         if ($exception === $handlerException) {
             self::$reservedMemory = null; // Disable the fatal error handler
             throw $exception; // Give back $exception to the native handler

src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php

@@ -530,4 +530,17 @@ public function testLegacyInterface()
             throw $e;
         }
     }
+
+    /**
+     * @expectedException \Exception
+     */
+    public function testCustomExceptionHandler()
+    {
+        $handler = new ErrorHandler();
+        $handler->setExceptionHandler(function ($e) use ($handler) {
+            $handler->handleException($e);
+        });
+
+        $handler->handleException(new \Exception());
+    }
 }