Merge branch '2.3' into 2.7

* 2.3:
  [PropertyAccess] ->getValue() should be read-only
  [Config] Fix XmlUtilsTest namespace
  [Routing] add query param if value is different from default

Conflicts:
	src/Symfony/Component/PropertyAccess/Tests/PropertyAccessorTest.php

Author: nicolas-grekas

PropertyAccessor.php

@@ -373,10 +373,11 @@ private function readPropertiesUntil($zval, PropertyPathInterface $propertyPath,
                     }
 
                     if ($i + 1 < $propertyPath->getLength()) {
-                        $zval[self::VALUE][$property] = array();
-
                         if (isset($zval[self::REF])) {
+                            $zval[self::VALUE][$property] = array();
                             $zval[self::REF] = $zval[self::VALUE];
+                        } else {
+                            $zval[self::VALUE] = array($property => array());
                         }
                     }
                 }

Tests/PropertyAccessorTest.php

@@ -126,6 +126,15 @@ public function testGetValueReadsMagicGet()
         $this->assertSame('Bernhard', $this->propertyAccessor->getValue(new TestClassMagicGet('Bernhard'), 'magicProperty'));
     }
 
+    public function testGetValueReadsArrayWithMissingIndexForCustomPropertyPath()
+    {
+        $object = new \ArrayObject();
+        $array = array('child' => array('index' => $object));
+
+        $this->assertNull($this->propertyAccessor->getValue($array, '[child][index][foo][bar]'));
+        $this->assertSame(array(), $object->getArrayCopy());
+    }
+
     // https://github.com/symfony/symfony/pull/4450
     public function testGetValueReadsMagicGetThatReturnsConstant()
     {