[4] redo the logic behind Empty State Queries.

administrator/components/com_categories/src/Model/CategoriesModel.php

@@ -17,6 +17,7 @@
 use Joomla\CMS\Language\Associations;
 use Joomla\CMS\MVC\Factory\MVCFactoryInterface;
 use Joomla\CMS\MVC\Model\ListModel;
+use Joomla\Database\DatabaseQuery;
 use Joomla\Database\ParameterType;
 use Joomla\Utilities\ArrayHelper;
 
@@ -490,30 +491,28 @@ public function countItems(&$items, $extension)
 	}
 
 	/**
-	 * Is this an empty state, I.e: no items of this type regardless of the searched for states.
+	 * Manipulate the query to be used to evaluate if this is an Empty State to provide specific conditions for this extension.
 	 *
-	 * @return boolean
+	 * @return DatabaseQuery
 	 *
 	 * @since __DEPLOY_VERSION__
 	 */
-	public function getisEmptyState()
+	protected function getEmptyStateQuery(): DatabaseQuery
 	{
-		$extension = $this->getState('filter.extension');
+		$query = parent::getEmptyStateQuery();
 
-		$sql = $this->query
-			->clear('select')
-			->clear('values')
-			->clear('bounded')
-			->clear('limit')
-			->clear('order')
-			->clear('where')
-			->select('count(*)');
+		// Remove select because it contains fields from joined tables, that have been removed from join.
+		$query->clear('select');
 
-		$sql->where($this->_db->quoteName('extension') . ' = :extension')
-			->bind(':extension', $extension);
+		// Add back a simple count select.
+		$query->select('count(*)');
+
+		// Get the extension from the filter
+		$extension = $this->getState('filter.extension');
 
-		$this->_db->setQuery($sql);
+		$query->where($this->_db->quoteName('extension') . ' = :extension')
+			->bind(':extension', $extension);
 
-		return !($this->_db->loadResult() > 0);
+		return $query;
 	}
 }

administrator/components/com_tags/src/Model/TagsModel.php

@@ -16,6 +16,7 @@
 use Joomla\CMS\MVC\Factory\MVCFactoryInterface;
 use Joomla\CMS\MVC\Model\ListModel;
 use Joomla\CMS\Tag\TagServiceInterface;
+use Joomla\Database\DatabaseQuery;
 use Joomla\Database\ParameterType;
 
 /**
@@ -327,27 +328,15 @@ public function countItems(&$items, $extension)
 	}
 
 	/**
-	 * Is this an empty state, I.e: no items of this type regardless of the searched for states.
+	 * Manipulate the query to be used to evaluate if this is an Empty State to provide specific conditions for this extension.
 	 *
-	 * @return boolean
+	 * @return DatabaseQuery
 	 *
 	 * @since __DEPLOY_VERSION__
 	 */
-	public function getisEmptyState()
+	protected function getEmptyStateQuery(): DatabaseQuery
 	{
-		$sql = $this->query
-			->clear('select')
-			->clear('values')
-			->clear('bounded')
-			->clear('limit')
-			->clear('order')
-			->clear('where')
-			->select('count(*)');
-
-		$sql->where($this->_db->quoteName('alias') . ' != ' . $this->_db->quote('root'));
-
-		$this->_db->setQuery($sql);
-
-		return !($this->_db->loadResult() > 0);
+		return parent::getEmptyStateQuery()
+			->where($this->_db->quoteName('alias') . ' != ' . $this->_db->quote('root'));
 	}
 }

libraries/src/MVC/Model/ListModel.php

@@ -10,6 +10,7 @@
 
 \defined('JPATH_PLATFORM') or die;
 
+use Exception;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Filter\InputFilter;
 use Joomla\CMS\Form\Form;
@@ -118,7 +119,7 @@ class ListModel extends BaseDatabaseModel implements ListModelInterface
 	 * @param   MVCFactoryInterface  $factory  The factory.
 	 *
 	 * @since   1.6
-	 * @throws  \Exception
+	 * @throws  Exception
 	 */
 	public function __construct($config = array(), MVCFactoryInterface $factory = null)
 	{
@@ -149,27 +150,56 @@ public function __construct($config = array(), MVCFactoryInterface $factory = nu
 		}
 	}
 
+	/**
+	 * Provide a query to be used to evaluate if this is an Empty State, can be overridden in the model to provide granular control.
+	 *
+	 * @return DatabaseQuery
+	 *
+	 * @since __DEPLOY_VERSION__
+	 */
+	protected function getEmptyStateQuery(): DatabaseQuery
+	{
+		$query = clone $this->_getListQuery();
+
+		if ($query instanceof DatabaseQuery)
+		{
+			$query->clear('bounded')
+				->clear('group')
+				->clear('having')
+				->clear('join')
+				->clear('limit')
+				->clear('offset')
+				->clear('values')
+				->clear('where');
+		}
+
+		return $query;
+	}
+
 	/**
 	 * Is this an empty state, I.e: no items of this type regardless of the searched for states.
 	 *
 	 * @return boolean
 	 *
+	 * @throws Exception
+	 *
 	 * @since __DEPLOY_VERSION__
 	 */
-	public function getIsEmptyState()
+	public function getIsEmptyState(): bool
 	{
-		$sql = $this->query
-			->clear('select')
-			->clear('values')
-			->clear('bounded')
-			->clear('limit')
-			->clear('order')
-			->clear('where')
-			->select('count(*)');
-
-		$this->_db->setQuery($sql);
-
-		return !($this->_db->loadResult() > 0);
+		static $state;
+
+		if (empty($state))
+		{
+			$state = !($this->_getListCount($this->getEmptyStateQuery()));
+		}
+
+		if (true === $state)
+		{
+			$this->resetState($this->getActiveFilters(), true);
+		}
+
+		return $state;
 	}
 
 	/**

libraries/src/MVC/Model/StateBehaviorTrait.php

@@ -10,6 +10,7 @@
 
 \defined('JPATH_PLATFORM') or die;
 
+use Joomla\CMS\Factory;
 use Joomla\CMS\Object\CMSObject;
 
 /**
@@ -99,4 +100,29 @@ public function setState($property, $value = null)
 	protected function populateState()
 	{
 	}
+
+	/**
+	 * Reset active filter states.
+	 *
+	 * @param   array    $activefilters  The array of filters to clear.
+	 * @param   boolean  $session        Should we clear the userState also.
+	 *
+	 * @throws \Exception
+	 *
+	 * @since __DEPLOY_VERSION__
+	 */
+	public function resetState(array $activefilters, bool $session = false): void
+	{
+		$app = Factory::getApplication();
+
+		foreach ($activefilters as $activefilter => $filterstate)
+		{
+			if ($session === true)
+			{
+				$app->setUserState($this->context . '.filter.' . $activefilter, '');
+			}
+
+			$this->setState('filter.' . $activefilter, '');
+		}
+	}
 }