Merge branch '3.3' into 3.4

* 3.3:
  [HttpKernel] DebugHandlersListener should always replace the existing exception handler
  fix the Composer API being used
  [Debug] Always decorate existing exception handlers to deal with fatal errors
  Enableable ArrayNodeDefinition is disabled for empty configuration
  Fixing a bug where the dump() function depended on bundle ordering
  [Cache] Fix handling of apcu_fetch() edgy behavior
  Add nn (Norwegian Nynorsk) translation files, and improve existing file
  Problem in phar see mergerequest #25579
  [Form] Disallow transform dates beyond the year 9999
  Copied NO language files to the new NB locale.
  [Serializer] DateTimeNormalizer handling of null and empty values (returning null or empty instead of new object)
  [Console] Improve phpdoc on StyleInterface::ask()

Author: nicolas-grekas

Normalizer/DateTimeNormalizer.php

@@ -83,6 +83,10 @@ public function denormalize($data, $class, $format = null, array $context = arra
         $dateTimeFormat = isset($context[self::FORMAT_KEY]) ? $context[self::FORMAT_KEY] : null;
         $timezone = $this->getTimezone($context);
 
+        if ('' === $data || null === $data) {
+            throw new UnexpectedValueException('The data is either an empty string or null, you should pass a string that can be parsed with the passed format or a valid DateTime string.');
+        }
+
         if (null !== $dateTimeFormat) {
             if (null === $timezone && PHP_VERSION_ID < 70000) {
                 // https://bugs.php.net/bug.php?id=68669

Tests/Normalizer/DateTimeNormalizerTest.php

@@ -167,6 +167,24 @@ public function testDenormalizeInvalidDataThrowsException()
         $this->normalizer->denormalize('invalid date', \DateTimeInterface::class);
     }
 
+    /**
+     * @expectedException \Symfony\Component\Serializer\Exception\UnexpectedValueException
+     * @expectedExceptionMessage The data is either an empty string or null, you should pass a string that can be parsed with the passed format or a valid DateTime string.
+     */
+    public function testDenormalizeNullThrowsException()
+    {
+        $this->normalizer->denormalize(null, \DateTimeInterface::class);
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Serializer\Exception\UnexpectedValueException
+     * @expectedExceptionMessage The data is either an empty string or null, you should pass a string that can be parsed with the passed format or a valid DateTime string.
+     */
+    public function testDenormalizeEmptyStringThrowsException()
+    {
+        $this->normalizer->denormalize('', \DateTimeInterface::class);
+    }
+
     /**
      * @expectedException \Symfony\Component\Serializer\Exception\UnexpectedValueException
      */