bug #21527 [Config] Fix conditional class existence checks (nicolas-g…

…rekas)

This PR was merged into the 3.3-dev branch.

Discussion
----------

[Config] Fix conditional class existence checks

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

Commits
-------

686af61 [Config] Fix conditional class existence checks

src/Symfony/Component/Config/Resource/ClassExistenceResource.php

@@ -28,8 +28,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     private $resource;
     private $existsStatus;
 
-    private static $checkingLevel = 0;
-    private static $throwingAutoloader;
+    private static $autoloadLevel = 0;
     private static $existsCache = array();
 
     /**
@@ -68,21 +67,17 @@ public function isFresh($timestamp)
         if (null !== $exists = &self::$existsCache[$this->resource]) {
             $exists = $exists || class_exists($this->resource, false) || interface_exists($this->resource, false) || trait_exists($this->resource, false);
         } elseif (self::EXISTS_KO_WITH_THROWING_AUTOLOADER === $this->existsStatus) {
-            if (null === self::$throwingAutoloader) {
-                $signalingException = new \ReflectionException();
-                self::$throwingAutoloader = function () use ($signalingException) { throw $signalingException; };
-            }
-            if (!self::$checkingLevel++) {
-                spl_autoload_register(self::$throwingAutoloader);
+            if (!self::$autoloadLevel++) {
+                spl_autoload_register('Symfony\Component\Config\Resource\ClassExistenceResource::throwOnRequiredClass');
             }
 
             try {
                 $exists = class_exists($this->resource) || interface_exists($this->resource, false) || trait_exists($this->resource, false);
             } catch (\ReflectionException $e) {
                 $exists = false;
             } finally {
-                if (!--self::$checkingLevel) {
-                    spl_autoload_unregister(self::$throwingAutoloader);
+                if (!--self::$autoloadLevel) {
+                    spl_autoload_unregister('Symfony\Component\Config\Resource\ClassExistenceResource::throwOnRequiredClass');
                 }
             }
         } else {
@@ -115,4 +110,40 @@ public function unserialize($serialized)
     {
         list($this->resource, $this->existsStatus) = unserialize($serialized);
     }
+
+    /**
+     * @throws \ReflectionException When $class is not found and is required
+     */
+    private static function throwOnRequiredClass($class)
+    {
+        $e = new \ReflectionException("Class $class does not exist");
+        $trace = $e->getTrace();
+        $autoloadFrame = array(
+            'function' => 'spl_autoload_call',
+            'args' => array($class),
+        );
+        $i = 1 + array_search($autoloadFrame, $trace, true);
+
+        if (isset($trace[$i]['function']) && !isset($trace[$i]['class'])) {
+            switch ($trace[$i]['function']) {
+                case 'get_class_methods':
+                case 'get_class_vars':
+                case 'get_parent_class':
+                case 'is_a':
+                case 'is_subclass_of':
+                case 'class_exists':
+                case 'class_implements':
+                case 'class_parents':
+                case 'trait_exists':
+                case 'defined':
+                case 'interface_exists':
+                case 'method_exists':
+                case 'property_exists':
+                case 'is_callable':
+                    return;
+            }
+        }
+
+        throw $e;
+    }
 }

src/Symfony/Component/Config/Tests/Fixtures/Resource/ConditionalClass.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Symfony\Component\Config\Tests\Fixtures\Resource;
+
+if (!class_exists(MissingClass::class)) {
+    class ConditionalClass
+    {
+    }
+}

src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Config\Tests\Resource;
 
 use Symfony\Component\Config\Resource\ClassExistenceResource;
+use Symfony\Component\Config\Tests\Fixtures\Resource\ConditionalClass;
 
 class ClassExistenceResourceTest extends \PHPUnit_Framework_TestCase
 {
@@ -71,4 +72,11 @@ public function testExistsKo()
             spl_autoload_unregister($autoloader);
         }
     }
+
+    public function testConditionalClass()
+    {
+        $res = new ClassExistenceResource(ConditionalClass::class, ClassExistenceResource::EXISTS_KO_WITH_THROWING_AUTOLOADER);
+
+        $this->assertFalse($res->isFresh(0));
+    }
 }