[HttpKernel] DebugHandlersListener should always replace the existing exception handler

ErrorHandler.php

@@ -147,11 +147,14 @@ class ErrorHandler
             $handler = $prev[0];
             $replace = false;
         }
-        if ($replace || !$prev) {
-            $handler->setExceptionHandler(set_exception_handler(array($handler, 'handleException')));
-        } else {
+        if (!$replace && $prev) {
             restore_error_handler();
         }
+        if (is_array($prev = set_exception_handler(array($handler, 'handleException'))) && $prev[0] === $handler) {
+            restore_exception_handler();
+        } else {
+            $handler->setExceptionHandler($prev);
+        }
 
         $handler->throwAt($levels & $handler->thrownErrors, true);
 
@@ -561,6 +564,8 @@ class ErrorHandler
 
         $handler = self::$reservedMemory = null;
         $handlers = array();
+        $previousHandler = null;
+        $sameHandlerLimit = 10;
 
         while (!is_array($handler) || !$handler[0] instanceof self) {
             $handler = set_exception_handler('var_dump');
@@ -570,7 +575,14 @@ class ErrorHandler
                 break;
             }
             restore_exception_handler();
-            array_unshift($handlers, $handler);
+
+            if ($handler !== $previousHandler) {
+                array_unshift($handlers, $handler);
+                $previousHandler = $handler;
+            } elseif (0 === --$sameHandlerLimit) {
+                $handler = null;
+                break;
+            }
         }
         foreach ($handlers as $h) {
             set_exception_handler($h);

Tests/ErrorHandlerTest.php

@@ -293,6 +293,9 @@ class ErrorHandlerTest extends TestCase
         @$handler->handleError(E_USER_DEPRECATED, 'Foo deprecation', __FILE__, __LINE__, array());
     }
 
+    /**
+     * @group no-hhvm
+     */
     public function testHandleException()
     {
         try {
@@ -375,6 +378,9 @@ class ErrorHandlerTest extends TestCase
         }
     }
 
+    /**
+     * @group no-hhvm
+     */
     public function testHandleFatalError()
     {
         try {
@@ -434,6 +440,9 @@ class ErrorHandlerTest extends TestCase
         $this->assertStringStartsWith("Attempted to load class \"Foo\" from the global namespace.\nDid you forget a \"use\" statement", $args[0]->getMessage());
     }
 
+    /**
+     * @group no-hhvm
+     */
     public function testHandleFatalErrorOnHHVM()
     {
         try {

Tests/phpt/decorate_exception_hander.phpt

@@ -0,0 +1,47 @@
+--TEST--
+Test catching fatal errors when handlers are nested
+--FILE--
+<?php
+
+namespace Symfony\Component\Debug;
+
+$vendor = __DIR__;
+while (!file_exists($vendor.'/vendor')) {
+    $vendor = dirname($vendor);
+}
+require $vendor.'/vendor/autoload.php';
+
+set_error_handler('var_dump');
+set_exception_handler('var_dump');
+
+ErrorHandler::register(null, false);
+
+if (true) {
+    class foo extends missing
+    {
+    }
+}
+
+?>
+--EXPECTF--
+Fatal error: Class 'Symfony\Component\Debug\missing' not found in %s on line %d
+object(Symfony\Component\Debug\Exception\ClassNotFoundException)#%d (8) {
+  ["message":protected]=>
+  string(131) "Attempted to load class "missing" from namespace "Symfony\Component\Debug".
+Did you forget a "use" statement for another namespace?"
+  ["string":"Exception":private]=>
+  string(0) ""
+  ["code":protected]=>
+  int(0)
+  ["file":protected]=>
+  string(%d) "%s"
+  ["line":protected]=>
+  int(%d)
+  ["trace":"Exception":private]=>
+  array(0) {
+  }
+  ["previous":"Exception":private]=>
+  NULL
+  ["severity":protected]=>
+  int(1)
+}

Tests/phpt/fatal_with_nested_handlers.phpt

@@ -35,7 +35,7 @@ array(1) {
   [0]=>
   string(37) "Error and exception handlers do match"
 }
-object(Symfony\Component\Debug\Exception\FatalErrorException)#4 (8) {
+object(Symfony\Component\Debug\Exception\FatalErrorException)#%d (8) {
   ["message":protected]=>
   string(199) "Error: Class Symfony\Component\Debug\Broken contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (Serializable::serialize, Serializable::unserialize)"
 %a