Issue #2086305 by larowlan: Add a FloatItem data type.

core/lib/Drupal/Core/Entity/Plugin/DataType/FloatItem.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Entity\Plugin\DataType\FloatItem.
+ */
+
+namespace Drupal\Core\Entity\Plugin\DataType;
+
+use Drupal\Core\TypedData\Annotation\DataType;
+use Drupal\Core\Annotation\Translation;
+use Drupal\Core\Entity\Field\FieldItemBase;
+
+/**
+ * Defines the 'float_field' entity field item.
+ *
+ * @DataType(
+ *   id = "float_field",
+ *   label = @Translation("Float field item"),
+ *   description = @Translation("An entity field containing an float value."),
+ *   list_class = "\Drupal\Core\Entity\Field\Field"
+ * )
+ */
+class FloatItem extends FieldItemBase {
+
+  /**
+   * Definitions of the contained properties.
+   *
+   * @see IntegerItem::getPropertyDefinitions()
+   *
+   * @var array
+   */
+  static $propertyDefinitions;
+
+  /**
+   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
+   */
+  public function getPropertyDefinitions() {
+
+    if (!isset(static::$propertyDefinitions)) {
+      static::$propertyDefinitions['value'] = array(
+        'type' => 'float',
+        'label' => t('Float value'),
+      );
+    }
+    return static::$propertyDefinitions;
+  }
+}

core/modules/system/lib/Drupal/system/Tests/TypedData/TypedDataTest.php

@@ -569,12 +569,12 @@ public function testTypedDataValidation() {
 
     // Test the Null constraint with typed data containers.
     $definition = array(
-      'type' => 'integer_field',
+      'type' => 'float_field',
       'constraints' => array(
         'Null' => array(),
       ),
     );
-    $field_item = $this->typedData->create($definition, array('value' => 10));
+    $field_item = $this->typedData->create($definition, array('value' => 11.5));
     $violations = $field_item->validate();
     $this->assertEqual($violations->count(), 1);
     $field_item = $this->typedData->create($definition);