diff --git a/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php b/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
index e61d6c9..066ed0a 100644
--- a/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
+++ b/core/lib/Drupal/Core/TypedData/Validation/ExecutionContext.php
@@ -241,8 +241,8 @@ public function getPropertyName() {
   /**
    * {@inheritdoc}
    */
-  public function getPropertyPath($subPath = '') {
-    return PropertyPath::append($this->propertyPath, $subPath);
+  public function getPropertyPath($sub_path = '') {
+    return PropertyPath::append($this->propertyPath, $sub_path);
   }
 
   /**
@@ -262,15 +262,15 @@ public function validate($value, $subPath = '', $groups = NULL, $traverse = FALS
   /**
    * {@inheritdoc}
    */
-  public function markConstraintAsValidated($cacheKey, $constraintHash) {
-    $this->validatedConstraints[$cacheKey . ':' . $constraintHash] = TRUE;
+  public function markConstraintAsValidated($cache_key, $constraint_hash) {
+    $this->validatedConstraints[$cache_key . ':' . $constraint_hash] = TRUE;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function isConstraintValidated($cacheKey, $constraintHash) {
-    return isset($this->validatedConstraints[$cacheKey . ':' . $constraintHash]);
+  public function isConstraintValidated($cache_key, $constraint_hash) {
+    return isset($this->validatedConstraints[$cache_key . ':' . $constraint_hash]);
   }
 
   /**
@@ -283,28 +283,28 @@ public function validateValue($value, $constraints, $subPath = '', $groups = NUL
   /**
    * {@inheritdoc}
    */
-  public function markGroupAsValidated($cacheKey, $groupHash) {
-    $this->validatedObjects[$cacheKey][$groupHash] = TRUE;
+  public function markGroupAsValidated($cache_key, $group_hash) {
+    $this->validatedObjects[$cache_key][$group_hash] = TRUE;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function isGroupValidated($cacheKey, $groupHash) {
-    return isset($this->validatedObjects[$cacheKey][$groupHash]);
+  public function isGroupValidated($cache_key, $group_hash) {
+    return isset($this->validatedObjects[$cache_key][$group_hash]);
   }
 
   /**
    * {@inheritdoc}
    */
-  public function markObjectAsInitialized($cacheKey) {
+  public function markObjectAsInitialized($cache_key) {
     // Not supported, so nothing todo.
   }
 
   /**
    * {@inheritdoc}
    */
-  public function isObjectInitialized($cacheKey) {
+  public function isObjectInitialized($cache_key) {
     // Not supported, so nothing todo.
   }
 
diff --git a/core/lib/Drupal/Core/TypedData/Validation/RecursiveContextualValidator.php b/core/lib/Drupal/Core/TypedData/Validation/RecursiveContextualValidator.php
index bbbd56f..22bc398 100644
--- a/core/lib/Drupal/Core/TypedData/Validation/RecursiveContextualValidator.php
+++ b/core/lib/Drupal/Core/TypedData/Validation/RecursiveContextualValidator.php
@@ -104,36 +104,37 @@ public function validate($data, $constraints = NULL, $groups = NULL) {
    * @return $this
    */
   protected function validateNode(TypedDataInterface $data, $constraints = NULL) {
-    $previousValue = $this->context->getValue();
-    $previousObject = $this->context->getObject();
-    $previousMetadata = $this->context->getMetadata();
-    $previousPath = $this->context->getPropertyPath();
+    $previous_value = $this->context->getValue();
+    $previous_object = $this->context->getObject();
+    $previous_metadata = $this->context->getMetadata();
+    $previous_path = $this->context->getPropertyPath();
 
     $metadata = $this->metadataFactory->getMetadataFor($data);
-    $cacheKey = spl_object_hash($data);
-    $propertyPath = PropertyPath::append($previousPath, $data->getName());
+    $cache_key = spl_object_hash($data);
+    $property_path = PropertyPath::append($previous_path, $data->getName());
     // Pass the canonical representation of the data as validated value to
     // constraint validators, such that they do not have to care about Typed
     // Data.
     $value = $this->typedDataManager->getCanonicalRepresentation($data);
-    $this->context->setNode($value, $data, $metadata, $propertyPath);
+    $this->context->setNode($value, $data, $metadata, $property_path);
 
-    if (!$this->context->isGroupValidated($cacheKey, Constraint::DEFAULT_GROUP)) {
-      $this->context->markGroupAsValidated($cacheKey, Constraint::DEFAULT_GROUP);
-
-      $constraints = isset($constraints) ? $constraints : $metadata->findConstraints(Constraint::DEFAULT_GROUP);
-      $this->validateConstraints($value, $cacheKey, $constraints);
+    if (isset($constraints) || !$this->context->isGroupValidated($cache_key, Constraint::DEFAULT_GROUP)) {
+      if (!isset($constraints)) {
+        $this->context->markGroupAsValidated($cache_key, Constraint::DEFAULT_GROUP);
+        $constraints = $metadata->findConstraints(Constraint::DEFAULT_GROUP);
+      }
+      $this->validateConstraints($value, $cache_key, $constraints);
     }
 
     // If the data is a list or complex data, validate the contained list items
-    // or properties.
-    if ($data instanceof TraversableTypedDataInterface) {
+    // or properties. However, do not recurse if the data is empty.
+    if (($data instanceof ListInterface || $data instanceof ComplexDataInterface) && !$data->isEmpty()) {
       foreach ($data as $name => $property) {
         $this->validateNode($property);
       }
     }
 
-    $this->context->setNode($previousValue, $previousObject, $previousMetadata, $previousPath);
+    $this->context->setNode($previous_value, $previous_object, $previous_metadata, $previous_path);
 
     return $this;
   }
@@ -144,18 +145,18 @@ protected function validateNode(TypedDataInterface $data, $constraints = NULL) {
    * @param mixed $value
    *   The validated value.
    */
-  protected function validateConstraints($value, $cacheKey, $constraints) {
+  protected function validateConstraints($value, $cache_key, $constraints) {
     foreach ($constraints as $constraint) {
       // Prevent duplicate validation of constraints, in the case
       // that constraints belong to multiple validated groups
-      if (null !== $cacheKey) {
-        $constraintHash = spl_object_hash($constraint);
+      if (isset($cache_key)) {
+        $constraint_hash = spl_object_hash($constraint);
 
-        if ($this->context->isConstraintValidated($cacheKey, $constraintHash)) {
+        if ($this->context->isConstraintValidated($cache_key, $constraint_hash)) {
           continue;
         }
 
-        $this->context->markConstraintAsValidated($cacheKey, $constraintHash);
+        $this->context->markConstraintAsValidated($cache_key, $constraint_hash);
       }
 
       $this->context->setConstraint($constraint);
diff --git a/core/modules/user/src/Tests/UserValidationTest.php b/core/modules/user/src/Tests/UserValidationTest.php
index 172b79d..ec44a79 100644
--- a/core/modules/user/src/Tests/UserValidationTest.php
+++ b/core/modules/user/src/Tests/UserValidationTest.php
@@ -122,9 +122,9 @@ function testValidation() {
     //   https://drupal.org/node/2023465.
     $this->assertEqual(count($violations), 2, 'Violations found when email is too long');
     $this->assertEqual($violations[0]->getPropertyPath(), 'mail.0.value');
-    $this->assertEqual($violations[0]->getMessage(), t('This value is not a valid email address.'));
+    $this->assertEqual($violations[0]->getMessage(), t('%name: the email address can not be longer than @max characters.', array('%name' => $user->get('mail')->getFieldDefinition()->getLabel(), '@max' => Email::EMAIL_MAX_LENGTH)));
     $this->assertEqual($violations[1]->getPropertyPath(), 'mail.0.value');
-    $this->assertEqual($violations[1]->getMessage(), t('%name: the email address can not be longer than @max characters.', array('%name' => $user->get('mail')->getFieldDefinition()->getLabel(), '@max' => Email::EMAIL_MAX_LENGTH)));
+    $this->assertEqual($violations[1]->getMessage(), t('This value is not a valid email address.'));
 
     // Provoke an email collision with an existing user.
     $user->set('mail', 'existing@example.com');