merged branch ShiraNai7/master (PR #8688)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #8688).

Discussion
----------

[Debug] Make sure ContextErrorException is loaded during compile time errors

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

### Description

When the `ErrorHandler->handle()` attempts to throw a `ContextErrorException` the script might die with a Fatal Error because the class is not found.

    FatalErrorException: Error: Class 'Symfony\Component\Debug\Exception\ContextErrorException' not found in ...

That effectively hides the original error and causes confusion.

### Cause

The cause is a bug/limitation of PHP that makes class autoloading completely inactive during "compiling".

Relevant PHP source code in `zend_execute_API.c`:

    /* The compiler is not-reentrant. Make sure we __autoload() only during run-time
     * (doesn't impact functionality of __autoload()
    */
    if (!use_autoload || zend_is_compiling(TSRMLS_C)) {

#### More information about the PHP bug/limitation:
- https://bugs.php.net/bug.php?id=65322
- many duplicates/relevant: https://www.google.com/search?btnG=1&pws=0&q=site%3Abugs.php.net+autoload+error+handling

### The fix

The most simple way to fix this is to manually ensure that `ContextErrorException` is loaded and if not, load it. This is what I did.

Another way is to detect if autoloading is available (possible by prepending a temporary autoloader) and act accordingly (how?).

### The test

I also added a test case that would fail with a fatal error if the error handler does not successfully throw an exception in case of a compile time error. But I'm not sure if this is the best way or if there should be a test case at all.

###

Commits
-------

b0082ab [Debug] Make sure ContextErrorException is loaded during compile time errors

src/Symfony/Component/Debug/ErrorHandler.php

@@ -120,6 +120,11 @@ class ErrorHandler
         }
 
         if ($this->displayErrors && error_reporting() & $level && $this->level & $level) {
+            // make sure the ContextErrorException class is loaded (https://bugs.php.net/bug.php?id=65322)
+            if (!class_exists('Symfony\Component\Debug\Exception\ContextErrorException')) {
+                require __DIR__.'/Exception/ContextErrorException.php';
+            }
+
             throw new ContextErrorException(sprintf('%s: %s in %s line %d', isset($this->levels[$level]) ? $this->levels[$level] : $level, $message, $file, $line), 0, $level, $file, $line, $context);
         }
 

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

@@ -20,6 +20,31 @@ use Symfony\Component\Debug\ErrorHandler;
  */
 class ErrorHandlerTest extends \PHPUnit_Framework_TestCase
 {
+    public function testCompileTimeError()
+    {
+        // the ContextErrorException must not be loaded for this test to work
+        if (class_exists('Symfony\Component\Debug\Exception\ContextErrorException', false)) {
+            $this->markTestSkipped('The ContextErrorException class is already loaded.');
+        }
+    
+        $handler = ErrorHandler::register(E_ALL | E_STRICT);
+        $displayErrors = ini_get('display_errors');
+        ini_set('display_errors', '1');
+
+        try {
+            // trigger compile time error
+            eval(<<<'PHP'
+class _BaseCompileTimeError { function foo() {} }
+class _CompileTimeError extends _BaseCompileTimeError { function foo($invalid) {} }
+PHP
+            );
+        } catch(\Exception $e) {
+            // if an exception is thrown, the test passed
+        }
+
+        ini_set('display_errors', $displayErrors);
+        restore_error_handler();
+    }
 
     public function testConstruct()
     {