diff --git a/core/lib/Drupal/Core/Field/FieldItemListComputed.php b/core/lib/Drupal/Core/Field/FieldItemListComputed.php
new file mode 100644
index 0000000..b00dc30
--- /dev/null
+++ b/core/lib/Drupal/Core/Field/FieldItemListComputed.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Drupal\Core\Field;
+
+use Drupal\Core\Form\FormStateInterface;
+
+abstract class FieldItemListComputed extends FieldItemList implements FieldItemListComputedInterface {
+  /**
+   * Numerically indexed array of field items.
+   *
+   * @var \Drupal\Core\Field\FieldItemInterface[]
+   */
+  protected $list = array();
+
+  /**
+   * {@inheritdoc}
+   */
+  public function computeItems() {
+    $this->list = [];
+    $values = $this->computeItemValues();
+    if (is_array($values) && !empty($values)) {
+      foreach ($values AS $delta => $value) {
+        $this->list[] = $this->createItem($delta, $value);
+      }
+    }
+  }
+
+  /**
+   * This should compute the values that are used to create the field items.
+   *
+   * @return array The values for the field items.
+   */
+  protected abstract function computeItemValues();
+
+  /**
+   * This will do nothing as computed lists are readonly bz default.
+   */
+  public function setValue($values, $notify = TRUE) {}
+
+  /**
+   * This will do nothing as computed lists are readonly bz default.
+   */
+  public function appendItem($value = NULL) {}
+
+  /**
+   * This will do nothing as computed lists are readonly bz default.
+   */
+  public function defaultValuesForm(array &$form, FormStateInterface $form_state) {}
+
+  /**
+   * This will do nothing as computed lists are readonly bz default.
+   */
+  public function removeItem($index) {}
+
+  /**
+   * This will do nothing as computed lists are readonly bz default.
+   */
+  public function set($index, $value) {}
+}
diff --git a/core/lib/Drupal/Core/Field/FieldItemListComputedInterface.php b/core/lib/Drupal/Core/Field/FieldItemListComputedInterface.php
new file mode 100644
index 0000000..f6a6769
--- /dev/null
+++ b/core/lib/Drupal/Core/Field/FieldItemListComputedInterface.php
@@ -0,0 +1,9 @@
+<?php
+namespace Drupal\Core\Field;
+
+interface FieldItemListComputedInterface {
+  /**
+   * This will populate the field item list with computed values.
+   */
+  public function computeItems();
+}
diff --git a/core/lib/Drupal/Core/TypedData/TypedDataManager.php b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
index 7fe362e..552098d 100644
--- a/core/lib/Drupal/Core/TypedData/TypedDataManager.php
+++ b/core/lib/Drupal/Core/TypedData/TypedDataManager.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\DependencyInjection\ClassResolverInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Field\FieldItemListComputed;
 use Drupal\Core\Plugin\DefaultPluginManager;
 use Drupal\Core\TypedData\Validation\MetadataFactory;
 use Drupal\Core\Validation\ConstraintManager;
@@ -309,6 +310,9 @@ public function getPropertyInstance(TypedDataInterface $object, $property_name,
     $property->setContext($property_name, $object);
     if (isset($value)) {
       $property->setValue($value, FALSE);
+    } elseif ($property instanceof FieldItemListComputed) {
+      // populate the computed list with values as there are no initial values to set.
+      $property->computeItems();
     }
     return $property;
   }
diff --git a/core/modules/field/tests/modules/field_computed_test/src/Plugin/Field/FieldType/DiceFieldItemList.php b/core/modules/field/tests/modules/field_computed_test/src/Plugin/Field/FieldType/DiceFieldItemList.php
index 242ade0..06a125d 100644
--- a/core/modules/field/tests/modules/field_computed_test/src/Plugin/Field/FieldType/DiceFieldItemList.php
+++ b/core/modules/field/tests/modules/field_computed_test/src/Plugin/Field/FieldType/DiceFieldItemList.php
@@ -2,30 +2,21 @@
 
 namespace Drupal\field_computed_test\Plugin\Field\FieldType;
 
-use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\Field\FieldItemListComputed;
 
 /**
  * Represents a configurable dice result.
  */
-class DiceFieldItemList extends FieldItemList {
-
+class DiceFieldItemList extends FieldItemListComputed {
   /**
    * {@inheritdoc}
    */
-  public function getValue($include_computed = FALSE) {
+  protected function computeItemValues() {
     $items_count = $this->getParent()->getValue()->field_dice_count->value;
-    $values = array();
+    $values = [];
     foreach (range(0, $items_count - 1) as $delta) {
       $values[$delta] = rand(1, 6);
     }
     return $values;
   }
-
-  /**
-   * Implements \Countable::count().
-   */
-  public function count() {
-    $items_count = $this->getParent()->getValue()->field_dice_count->value;
-    return $items_count;
-  }
 }