Added ability to disable Symfony's error handler.

PHPUnit has built in support for testing if PHP errors are thrown by
looking for special exception classes:
  PHPUnit_Framework_Error
  PHPUnit_Framework_Warning
  PHPUnit_Framework_Notice

This support is only enabled if no other error handlers are registered.
The Symfony kernel registers an error handler by default, thus disabling
PHPUnit's special PHP error exceptions if the kernel has been booted.

This commit adds support for a new configuration parameter,
error_handler.enable, which can prevent the Symfony error handler from
registering if set to false.

After this commit, by default the error handler will be disabled in the
test environment.  To enable it, add the following to your
config_test.yml:

parameters:
  error_handler.enable:  true

src/Symfony/Foundation/Debug/ErrorHandler.php

@@ -42,9 +42,11 @@ public function __construct($level = null)
         $this->level = null === $level ? error_reporting() : $level;
     }
 
-    public function register()
+    public function register($enable=true)
     {
-        set_error_handler(array($this, 'handle'));
+        if($enable) {
+            set_error_handler(array($this, 'handle'));
+        }
     }
 
     /**

src/Symfony/Foundation/Resources/config/services.xml

@@ -11,6 +11,7 @@
         <parameter key="response.class">Symfony\Components\HttpKernel\Response</parameter>
         <parameter key="error_handler.class">Symfony\Foundation\Debug\ErrorHandler</parameter>
         <parameter key="error_handler.level">null</parameter>
+        <parameter key="error_handler.enable">true</parameter>
         <parameter key="kernel.include_core_classes">true</parameter>
     </parameters>
 
@@ -21,7 +22,9 @@
 
         <service id="error_handler" class="%error_handler.class%">
             <argument>%error_handler.level%</argument>
-            <call method="register" />
+            <call method="register">
+                <argument>%error_handler.enable%</argument>
+            </call>
         </service>
 
         <service id="http_kernel" class="%http_kernel.class%">

src/Symfony/Foundation/Resources/config/test.xml

@@ -9,6 +9,7 @@
         <parameter key="test.client.parameters" type="collection"></parameter>
         <parameter key="test.client.history.class">Symfony\Components\BrowserKit\History</parameter>
         <parameter key="test.client.cookiejar.class">Symfony\Components\BrowserKit\CookieJar</parameter>
+        <parameter key="error_handler.enable">false</parameter>
     </parameters>
 
     <services>

src/Symfony/Foundation/bootstrap.php

@@ -287,9 +287,11 @@ public function __construct($level = null)
         $this->level = null === $level ? error_reporting() : $level;
     }
 
-    public function register()
+    public function register($enable=true)
     {
-        set_error_handler(array($this, 'handle'));
+        if($enable) {
+            set_error_handler(array($this, 'handle'));
+        }
     }
 
 

tests/Symfony/Tests/Foundation/Debug/ErrorHandlerTest.php

@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Tests\Foundation\Debug;
+
+use Symfony\Foundation\Debug\ErrorHandler;
+
+class ErrorHandlerTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @covers Symfony\Foundation\Debug\ErrorHandler::register
+     */
+    public function testRegister()
+    {
+        $fakeHandler = function($errno, $errstr)
+        {
+            die('Fake error handler triggered');
+        };
+
+        $oldHandler = set_error_handler($fakeHandler);
+        restore_error_handler();
+
+        $handler = new ErrorHandler();
+        $handler->register(false);
+        $newHandler = set_error_handler($fakeHandler);
+        restore_error_handler();
+        $this->assertEquals($oldHandler, $newHandler);
+
+        $handler = new ErrorHandler();
+        $handler->register(true);
+        $newHandler = set_error_handler($fakeHandler);
+        restore_error_handler();
+        $this->assertNotEquals($oldHandler, $newHandler);
+        restore_error_handler();
+    }
+}