[Debug] Replaced logic for detecting filesystem case sensitivity

* 2.3:
  [HttpFoundation] Fix transient test
  [HttpFoundation] Add a dependency on the mbstring polyfill
  add readme files where missing
  Don't use reflections when possible
  [Form] Update form tests after the ICU data update
  [Intl] Update tests and the number formatter to match behaviour of the intl extension
  [Intl] Update the ICU data to version 55
  [Intl] Fix the update-data.php script in preparation for ICU 5.5
  Use constant instead of function call.
  fixed test name
  automatically generate safe fallback filename

Conflicts:
	src/Symfony/Component/Debug/Debug.php
	src/Symfony/Component/HttpFoundation/composer.json
	src/Symfony/Component/Serializer/Tests/Normalizer/GetSetMethodNormalizerTest.php

Debug.php

@@ -45,7 +45,7 @@ class Debug
             error_reporting(-1);
         }
 
-        if ('cli' !== php_sapi_name()) {
+        if ('cli' !== PHP_SAPI) {
             ini_set('display_errors', 0);
             ExceptionHandler::register();
         } elseif ($displayErrors && (!ini_get('log_errors') || ini_get('error_log'))) {

DebugClassLoader.php

@@ -51,7 +51,16 @@ class DebugClassLoader
         }
 
         if (!isset(self::$caseCheck)) {
-            self::$caseCheck = false !== stripos(PHP_OS, 'win') ? (false !== stripos(PHP_OS, 'darwin') ? 2 : 1) : 0;
+            if(!file_exists(strtolower(__FILE__))) {
+                // filesystem is case sensitive
+                self::$caseCheck = 0;
+            } elseif(realpath(strtolower(__FILE__)) === __FILE__) {
+                // filesystem is not case sensitive
+                self::$caseCheck = 1;
+            } else {
+                // filesystem is not case sensitive AND realpath() fails to normalize case
+                self::$caseCheck = 2;
+            }
         }
     }
 
@@ -193,16 +202,16 @@ class DebugClassLoader
                             break;
                     }
                 }
-                $parent = $refl->getParentClass();
+                $parent = get_parent_class($class);
 
-                if (!$parent || strncmp($ns, $parent->name, $len)) {
-                    if ($parent && isset(self::$deprecated[$parent->name]) && strncmp($ns, $parent->name, $len)) {
-                        @trigger_error(sprintf('The %s class extends %s that is deprecated %s', $name, $parent->name, self::$deprecated[$parent->name]), E_USER_DEPRECATED);
+                if (!$parent || strncmp($ns, $parent, $len)) {
+                    if ($parent && isset(self::$deprecated[$parent]) && strncmp($ns, $parent, $len)) {
+                        @trigger_error(sprintf('The %s class extends %s that is deprecated %s', $name, $parent, self::$deprecated[$parent]), E_USER_DEPRECATED);
                     }
 
-                    foreach ($refl->getInterfaceNames() as $interface) {
-                        if (isset(self::$deprecated[$interface]) && strncmp($ns, $interface, $len) && !($parent && $parent->implementsInterface($interface))) {
-                            @trigger_error(sprintf('The %s %s %s that is deprecated %s', $name, $refl->isInterface() ? 'interface extends' : 'class implements', $interface, self::$deprecated[$interface]), E_USER_DEPRECATED);
+                    foreach (class_implements($class) as $interface) {
+                        if (isset(self::$deprecated[$interface]) && strncmp($ns, $interface, $len) && !is_subclass_of($parent, $interface)) {
+                            @trigger_error(sprintf('The %s %s %s that is deprecated %s', $name, interface_exists($class) ? 'interface extends' : 'class implements', $interface, self::$deprecated[$interface]), E_USER_DEPRECATED);
                         }
                     }
                 }

README.md

@@ -1,42 +1,13 @@
 Debug Component
 ===============
 
-Debug provides tools to make debugging easier.
-
-Enabling all debug tools is as easy as calling the `enable()` method on the
-main `Debug` class:
-
-```php
-use Symfony\Component\Debug\Debug;
-
-Debug::enable();
-```
-
-You can also use the tools individually:
-
-```php
-use Symfony\Component\Debug\DebugClassLoader;
-use Symfony\Component\Debug\ErrorHandler;
-use Symfony\Component\Debug\ExceptionHandler;
-
-if ('cli' !== php_sapi_name()) {
-    ini_set('display_errors', 0);
-    ExceptionHandler::register();
-} elseif (!ini_get('log_errors') || ini_get('error_log')) {
-    ini_set('display_errors', 1);
-}
-ErrorHandler::register();
-DebugClassLoader::enable();
-```
-
-This component can optionally take advantage of the features of the HttpKernel
-and HttpFoundation components.
+The Debug component provides tools to ease debugging PHP code.
 
 Resources
 ---------
 
-You can run the unit tests with the following command:
-
-    $ cd path/to/Symfony/Component/Debug/
-    $ composer install
-    $ phpunit
+  * [Documentation](https://symfony.com/doc/current/components/debug/index.html)
+  * [Contributing](https://symfony.com/doc/current/contributing/index.html)
+  * [Report issues](https://github.com/symfony/symfony/issues) and
+    [send Pull Requests](https://github.com/symfony/symfony/pulls)
+    in the [main Symfony repository](https://github.com/symfony/symfony)