first commit

administrator/modules/mod_messages/mod_messages.php

@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  mod_messages
+ *
+ * @copyright   (C) 2019 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+\defined('_JEXEC') or die;
+
+use Joomla\CMS\Helper\ModuleHelper;
+
+// Check permissions.
+if (!$app->getIdentity()->authorise('core.login.admin') || !$app->getIdentity()->authorise('core.manage', 'com_messages')) {
+    return;
+}
+
+// Try to get the items from the messages model
+try {
+    /** @var \Joomla\Component\Messages\Administrator\Model\MessagesModel $messagesModel */
+    $messagesModel = $app->bootComponent('com_messages')->getMVCFactory()
+        ->createModel('Messages', 'Administrator', ['ignore_request' => true]);
+    $messagesModel->setState('filter.state', 0);
+    $messages = $messagesModel->getItems();
+} catch (RuntimeException $e) {
+    $messages = [];
+
+    // Still render the error message from the Exception object
+    $app->enqueueMessage($e->getMessage(), 'error');
+}
+
+$countUnread = \count($messages);
+
+require ModuleHelper::getLayoutPath('mod_messages', $params->get('layout', 'default'));

administrator/modules/mod_messages/mod_messages.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<extension type="module" client="administrator" method="upgrade">
+	<name>mod_messages</name>
+	<author>Joomla! Project</author>
+	<creationDate>2019-07</creationDate>
+	<copyright>(C) 2019 Open Source Matters, Inc.</copyright>
+	<license>GNU General Public License version 2 or later; see LICENSE.txt</license>
+	<authorEmail>admin@joomla.org</authorEmail>
+	<authorUrl>www.joomla.org</authorUrl>
+	<version>4.0.0</version>
+	<description>MOD_MESSAGES_XML_DESCRIPTION</description>
+	<files>
+		<filename module="mod_messages">mod_messages.php</filename>
+		<folder>tmpl</folder>
+	</files>
+	<languages>
+		<language tag="en-GB">language/en-GB/mod_messages.ini</language>
+		<language tag="en-GB">language/en-GB/mod_messages.sys.ini</language>
+	</languages>
+	<help key="Admin_Modules:_Messages" />
+	<config>
+		<fields name="params">
+			<fieldset name="advanced">
+				<field
+					name="layout"
+					type="modulelayout"
+					label="JFIELD_ALT_LAYOUT_LABEL"
+					class="form-select"
+				/>
+
+				<field
+					name="moduleclass_sfx"
+					type="textarea"
+					label="COM_MODULES_FIELD_MODULECLASS_SFX_LABEL"
+					rows="3"
+					validate="CssIdentifier"
+				/>
+			</fieldset>
+		</fields>
+	</config>
+</extension>

administrator/modules/mod_messages/tmpl/default.php

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+<?php
+
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  mod_messages
+ *
+ * @copyright   (C) 2019 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Language\Text;
+use Joomla\CMS\Router\Route;
+
+$hideLinks = $app->getInput()->getBool('hidemainmenu');
+
+if ($hideLinks || $countUnread < 1) {
+    return;
+}
+
+$route = 'index.php?option=com_messages&view=messages';
+?>
+<a class="header-item-content" href="<?php echo Route::_($route); ?>" title="<?php echo Text::_('MOD_MESSAGES_PRIVATE_MESSAGES'); ?>">
+    <div class="header-item-icon">
+        <div class="w-auto">
+            <span class="icon-envelope icon-fw" aria-hidden="true"></span>
+            <small class="header-item-count"><?php echo $countUnread; ?></small>
+        </div>
+    </div>
+    <div class="header-item-text">
+        <?php echo Text::_('MOD_MESSAGES_PRIVATE_MESSAGES'); ?>
+    </div>
+</a>