Add helper trait to provide type-hinting for zend-view

docs/book/flash-messenger-view-helper.md

@@ -144,3 +144,27 @@ data-dismiss="alert" aria-hidden="true">&times;</button><ul><li>',
     ],
 ],
 ```
+
+## IDE auto-completion in templates
+
+The `Zend\Mvc\Plugin\FlashMessenger\View\HelperTrait` trait can be used to
+provide auto-completion for modern IDEs. It defines the aliases of the view
+helpers in a DocBlock as `@method` tags.
+
+### Usage
+
+In order to allow auto-completion in templates, `$this` variable should be
+type-hinted via a DocBlock at the top of your template. It is recommended that
+you always add the `Zend\View\Renderer\PhpRenderer` as the first type, so that
+the IDE can auto-suggest the default view helpers from `zend-view`. Next, chain
+the `HelperTrait` from `zend-i18n` with a pipe symbol (a.k.a. vertical bar) `|`:
+
+```php
+/**
+ * @var Zend\View\Renderer\PhpRenderer|Zend\Mvc\Plugin\FlashMessenger\View\HelperTrait $this
+ */
+```
+
+You may chain as many `HelperTrait` traits as you like, depending on view
+helpers from which Zend Framework component you are using and would like to
+provide auto-completion for.

src/View/HelperTrait.php

@@ -0,0 +1,31 @@
+<?php
+/**
+ * @see       https://github.com/zendframework/zend-mvc-plugin-flashmessenger for the canonical source repository
+ * @copyright Copyright (c) 2018 Zend Technologies USA Inc. (http://www.zend.com)
+ * @license   https://github.com/zendframework/zend-mvc-plugin-flashmessenger/blob/master/LICENSE.md New BSD License
+ */
+
+namespace Zend\Mvc\Plugin\FlashMessenger\View;
+
+use Zend\Mvc\Plugin\FlashMessenger\FlashMessenger as PluginFlashMessenger;
+use Zend\Mvc\Plugin\FlashMessenger\View\Helper\FlashMessenger;
+
+/**
+ * Helper trait for auto-completion of code in modern IDEs.
+ *
+ * The trait provides convenience methods for view helpers,
+ * defined by the zend-mvc-plugin-flashmessenger component.
+ * It is designed to be used for type-hinting $this variable
+ * inside zend-view templates via doc blocks.
+ *
+ * The base class is PhpRenderer, followed by the helper trait from
+ * the zend-mvc-plugin-flashmessenger component. However, multiple helper traits
+ * from different Zend Framework components can be chained afterwards.
+ *
+ * @example @var \Zend\View\Renderer\PhpRenderer|\Zend\Mvc\Plugin\FlashMessenger\View\HelperTrait $this
+ *
+ * @method FlashMessenger|PluginFlashMessenger flashMessenger(string|null $namespace = null)
+ */
+trait HelperTrait
+{
+}