diff --git a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
index e28d9975b4..2ff671613e 100644
--- a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
@@ -12,7 +12,7 @@
 /**
  * A class for defining entity fields.
  */
-class BaseFieldDefinition extends ListDataDefinition implements FieldDefinitionInterface, FieldStorageDefinitionInterface {
+class BaseFieldDefinition extends ListDataDefinition implements FieldDefinitionInterface, FieldStorageDefinitionInterface, RequiredFieldStorageDefinitionInterface {
 
   use UnchangingCacheableDependencyTrait;
 
@@ -723,4 +723,30 @@ public function getConfig($bundle) {
     return BaseFieldOverride::createFromBaseFieldDefinition($this, $bundle);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isStorageRequired() {
+    if (isset($this->definition['storage_required'])) {
+      return (bool) $this->definition['storage_required'];
+    }
+
+    // Default to the 'required' property of the base field.
+    return $this->isRequired();
+  }
+
+  /**
+   * Sets whether the field storage is required.
+   *
+   * @param bool $required
+   *   Whether the field storage is required.
+   *
+   * @return static
+   *   The object itself for chaining.
+   */
+  public function setStorageRequired($required) {
+    $this->definition['storage_required'] = $required;
+    return $this;
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Field/RequiredFieldStorageDefinitionInterface.php b/core/lib/Drupal/Core/Field/RequiredFieldStorageDefinitionInterface.php
new file mode 100644
index 0000000000..d29e56907e
--- /dev/null
+++ b/core/lib/Drupal/Core/Field/RequiredFieldStorageDefinitionInterface.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+/**
+ * Defines an interface for required field storage definitions.
+ */
+interface RequiredFieldStorageDefinitionInterface {
+
+  /**
+   * Returns whether the field storage is required.
+   *
+   * If a field storage is required, NOT NULL constraints will be added
+   * automatically for the required properties of a field type.
+   *
+   * @return bool
+   *   TRUE if the field storage is required, FALSE otherwise.
+   */
+  public function isStorageRequired();
+
+}
diff --git a/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php b/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
index 6a54b3c502..fce3ddca40 100644
--- a/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
+++ b/core/modules/hal/src/Normalizer/ContentEntityNormalizer.php
@@ -215,11 +215,17 @@ protected function getTypedDataIds($types, $context = array()) {
       $types = array($types);
     }
 
+    if (empty($types)) {
+      throw new UnexpectedValueException('No entity type(s) specified');
+    }
+
     foreach ($types as $type) {
       if (!isset($type['href'])) {
         throw new UnexpectedValueException('Type must contain an \'href\' attribute.');
       }
+
       $type_uri = $type['href'];
+
       // Check whether the URI corresponds to a known type on this site. Break
       // once one does.
       if ($typed_data_ids = $this->linkManager->getTypeInternalIds($type['href'], $context)) {
diff --git a/core/modules/hal/tests/src/Functional/EntityResource/HalEntityNormalizationTrait.php b/core/modules/hal/tests/src/Functional/EntityResource/HalEntityNormalizationTrait.php
index d3bd85a9a9..836a1b4716 100644
--- a/core/modules/hal/tests/src/Functional/EntityResource/HalEntityNormalizationTrait.php
+++ b/core/modules/hal/tests/src/Functional/EntityResource/HalEntityNormalizationTrait.php
@@ -97,21 +97,18 @@ protected function assertNormalizationEdgeCases($method, Url $url, array $reques
     if ($this->entity->getEntityType()->hasKey('bundle')) {
       $normalization = $this->getNormalizedPostEntity();
 
-      // @todo Uncomment this in https://www.drupal.org/node/2824827.
-      // @codingStandardsIgnoreStart
-/*
+
       $normalization['_links']['type'] = Url::fromUri('base:rest/type/' . static::$entityTypeId . '/bad_bundle_name');
       $request_options[RequestOptions::BODY] = $this->serializer->encode($normalization, static::$format);
 
       // DX: 400 when incorrect entity type bundle is specified.
       $response = $this->request($method, $url, $request_options);
       // @todo Uncomment, remove next 3 in https://www.drupal.org/node/2813853.
-//      $this->assertResourceErrorResponse(400, 'The type link relation must be specified.', $response);
+      // $this->assertResourceErrorResponse(400, 'No entity type(s) specified', $response);
       $this->assertSame(400, $response->getStatusCode());
       $this->assertSame([static::$mimeType], $response->getHeader('Content-Type'));
-      $this->assertSame($this->serializer->encode(['error' => 'The type link relation must be specified.'], static::$format), (string) $response->getBody());
-*/
-      // @codingStandardsIgnoreEnd
+      $this->assertSame($this->serializer->encode(['error' => 'No entity type(s) specified'], static::$format), (string) $response->getBody());
+
 
       unset($normalization['_links']['type']);
       $request_options[RequestOptions::BODY] = $this->serializer->encode($normalization, static::$format);
diff --git a/core/modules/hal/tests/src/Kernel/DenormalizeTest.php b/core/modules/hal/tests/src/Kernel/DenormalizeTest.php
index 8f64049917..3f9388bce4 100644
--- a/core/modules/hal/tests/src/Kernel/DenormalizeTest.php
+++ b/core/modules/hal/tests/src/Kernel/DenormalizeTest.php
@@ -75,6 +75,36 @@ public function testTypeHandling() {
   }
 
   /**
+   * Tests link relation handling with an invalid type.
+   */
+  public function testTypeHandlingWithInvalidType() {
+    $data_with_invalid_type = array(
+      '_links' => array(
+        'type' => array(
+          'href' => Url::fromUri('base:rest/type/entity_test/entity_test_invalid', array('absolute' => TRUE))->toString(),
+        ),
+      ),
+    );
+
+    $this->setExpectedException(UnexpectedValueException::class);
+    $this->serializer->denormalize($data_with_invalid_type, $this->entityClass, $this->format);
+  }
+
+  /**
+   * Tests link relation handling with no types.
+   */
+  public function testTypeHandlingWithNoTypes() {
+    $data_with_no_types = array(
+      '_links' => array(
+        'type' => array(),
+      ),
+    );
+
+    $this->setExpectedException(UnexpectedValueException::class);
+    $this->serializer->denormalize($data_with_no_types, $this->entityClass, $this->format);
+  }
+
+  /**
    * Test that a field set to an empty array is different than an absent field.
    */
   public function testMarkFieldForDeletion() {
diff --git a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
index dbd50e795e..bb4668306b 100644
--- a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
@@ -255,6 +255,21 @@ public function testFieldRequired() {
   }
 
   /**
+   * Tests storage required.
+   *
+   * @covers ::isStorageRequired
+   * @covers ::setStorageRequired
+   */
+  public function testFieldStorageRequired() {
+    $definition = BaseFieldDefinition::create($this->fieldType);
+    $this->assertFalse($definition->isStorageRequired());
+    $definition->setStorageRequired(TRUE);
+    $this->assertTrue($definition->isStorageRequired());
+    $definition->setStorageRequired(FALSE);
+    $this->assertFalse($definition->isStorageRequired());
+  }
+
+  /**
    * Tests provider.
    *
    * @covers ::getProvider