Merge branch '3.3' into 3.4

* 3.3:
  Have weak_vendors ignore deprecations from outside
  [HttpFoundation] fixed return type of method HeaderBag::get
  [HttpFoundation] Added "resource" type on Request::create docblock
  [Process] Skip environment variables with false value in Process
  Revert "bug #25789  Enableable ArrayNodeDefinition is disabled for empty configuration (kejwmen)"
  Formatting fix in upgrade 3.0 document
  don't split lines on carriage returns when dumping
  Revert "bug #25851 [Validator] Conflict with egulias/email-validator 2.0 (emodric)"
  [DI] compilation perf tweak
  [Validator] Conflict with egulias/email-validator 2.0
  [Validator] add missing parent isset and add test

Author: nicolas-grekas

Constraint.php

@@ -214,6 +214,16 @@ public function __get($option)
         throw new InvalidOptionsException(sprintf('The option "%s" does not exist in constraint %s', $option, get_class($this)), array($option));
     }
 
+    /**
+     * @param string $option The option name
+     *
+     * @return bool
+     */
+    public function __isset($option)
+    {
+        return 'groups' === $option;
+    }
+
     /**
      * Adds the given group if this constraint is in the Default group.
      *

Tests/Constraints/FileTest.php

@@ -26,6 +26,16 @@ public function testMaxSize($maxSize, $bytes, $binaryFormat)
 
         $this->assertSame($bytes, $file->maxSize);
         $this->assertSame($binaryFormat, $file->binaryFormat);
+        $this->assertTrue($file->__isset('maxSize'));
+    }
+
+    public function testMagicIsset()
+    {
+        $file = new File(array('maxSize' => 1));
+
+        $this->assertTrue($file->__isset('maxSize'));
+        $this->assertTrue($file->__isset('groups'));
+        $this->assertFalse($file->__isset('toto'));
     }
 
     /**