Added system tags data structure and PHP side managers

Added SystemTagManager and SystemTagObjectMapper

8 files changed, 631 insertions, 5 deletions

diff --git a/lib/private/server.php b/lib/private/server.php
index ea5937dfea4..8171a00b3d1 100644
--- a/lib/private/server.php
+++ b/lib/private/server.php
@@ -138,6 +138,12 @@ class Server extends SimpleContainer implements IServerContainer {
 			$tagMapper = $c->query('TagMapper');
 			return new TagManager($tagMapper, $c->getUserSession());
 		});
+		$this->registerService('SystemTagManager', function (Server $c) {
+			return new SystemTag\SystemTagManager($c->getDatabaseConnection());
+		});
+		$this->registerService('SystemTagObjectMapper', function (Server $c) {
+			return new SystemTag\SystemTagObjectMapper($c->getDatabaseConnection(), $c->getSystemTagManager());
+		});
 		$this->registerService('RootFolder', function (Server $c) {
 			// TODO: get user and user manager from container as well
 			$user = \OC_User::getUser();
@@ -582,6 +588,29 @@ class Server extends SimpleContainer implements IServerContainer {
 	}
 
 	/**
+	 * Returns the system-tag manager
+	 *
+	 * @return \OCP\SystemTag\ISystemTagManager
+	 *
+	 * @since 9.0.0
+	 */
+	public function getSystemTagManager() {
+		return $this->query('SystemTagManager');
+	}
+
+	/**
+	 * Returns the system-tag object mapper
+	 *
+	 * @return \OCP\SystemTag\ISystemTagObjectMapper
+	 *
+	 * @since 9.0.0
+	 */
+	public function getSystemTagObjectMapper() {
+		return $this->query('SystemTagObjectMapper');
+	}
+
+
+	/**
 	 * Returns the avatar manager, used for avatar functionality
 	 *
 	 * @return \OCP\IAvatarManager
diff --git a/lib/private/systemtag/systemtag.php b/lib/private/systemtag/systemtag.php
new file mode 100644
index 00000000000..b79cc33cfb2
--- /dev/null
+++ b/lib/private/systemtag/systemtag.php
@@ -0,0 +1,90 @@
+<?php
+/**
+ * @author Vincent Petry <pvince81@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OC\SystemTag;
+
+use \OCP\IDBConnection;
+
+class SystemTag implements \OCP\SystemTag\ISystemTag {
+
+	/**
+	 * @var string
+	 */
+	private $id;
+
+	/**
+	 * @var string
+	 */
+	private $name;
+
+	/**
+	 * @var bool
+	 */
+	private $userVisible;
+
+	/**
+	 * @var bool
+	 */
+	private $userAssignable;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param string $id tag id
+	 * @param string $name tag name
+	 * @param bool $userVisible whether the tag is user visible
+	 * @param bool $userAssignable whether the tag is user assignable
+	 */
+	public function __construct($id, $name, $userVisible, $userAssignable) {
+		$this->id = $id;
+		$this->name = $name;
+		$this->userVisible = $userVisible;
+		$this->userAssignable = $userAssignable;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getId() {
+		return $this->id;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getName() {
+		return $this->name;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function isUserVisible() {
+		return $this->userVisible;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function isUserAssignable() {
+		return $this->userAssignable;
+	}
+}
diff --git a/lib/private/systemtag/systemtagmanager.php b/lib/private/systemtag/systemtagmanager.php
new file mode 100644
index 00000000000..e307825ecfa
--- /dev/null
+++ b/lib/private/systemtag/systemtagmanager.php
@@ -0,0 +1,264 @@
+<?php
+/**
+ * @author Vincent Petry <pvince81@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OC\SystemTag;
+
+use \OCP\IDBConnection;
+use \OCP\SystemTag\TagNotFoundException;
+use \OCP\SystemTag\TagAlreadyExistsException;
+
+use \Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+
+class SystemTagManager implements \OCP\SystemTag\ISystemTagManager {
+
+	const TAG_TABLE = 'systemtag';
+
+	/**
+	 * @var IDBConnection
+	 */
+	private $connection;
+
+	/**
+	 * Prepared query for selecting tags directly
+	 *
+	 * @var \OCP\DB\QueryBuilder\IQueryBuilder
+	 */
+	private $selectTagQuery;
+
+	/**
+	* Constructor.
+	*
+	* @param IDBConnection $connection database connection
+	*/
+	public function __construct(IDBConnection $connection) {
+		$this->connection = $connection;
+
+		$query = $this->connection->getQueryBuilder();
+		$this->selectTagQuery = $query->select('*')
+			->from(self::TAG_TABLE)
+			->where($query->expr()->eq('name', $query->createParameter('name')))
+			->andWhere($query->expr()->eq('visibility', $query->createParameter('visibility')))
+			->andWhere($query->expr()->eq('editable', $query->createParameter('editable')));
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getTagsById($tagIds) {
+		if (!is_array($tagIds)) {
+			$tagIds = [$tagIds];
+		}
+
+		$tags = [];
+
+		// note: not all databases will fail if it's a string or starts with a number
+		foreach ($tagIds as $tagId) {
+			if (!is_numeric($tagId)) {
+				throw new \InvalidArgumentException('Tag id must be integer');
+			}
+		}
+
+		$query = $this->connection->getQueryBuilder();
+		$query->select('*')
+			->from(self::TAG_TABLE)
+			->where($query->expr()->in('id', $query->createParameter('tagids')))
+			->addOrderBy('name', 'ASC')
+			->addOrderBy('visibility', 'ASC')
+			->addOrderBy('editable', 'ASC')
+			->setParameter('tagids', $tagIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY);
+
+		$result = $query->execute();
+		while ($row = $result->fetch()) {
+			$tags[$row['id']] = $this->createSystemTagFromRow($row);
+		}
+
+		$result->closeCursor();
+
+		if (count($tags) !== count($tagIds)) {
+			throw new TagNotFoundException(
+				'Tag(s) with id(s) ' . json_encode(array_diff($tagIds, array_keys($tags))) . ' not found'
+			);
+		}
+
+		return $tags;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getAllTags($visibilityFilter = null, $nameSearchPattern = null) {
+		$tags = [];
+
+		$query = $this->connection->getQueryBuilder();
+		$query->select('*')
+			->from(self::TAG_TABLE);
+
+		if (!is_null($visibilityFilter)) {
+			$query->andWhere($query->expr()->eq('visibility', $query->createNamedParameter((int)$visibilityFilter)));
+		}
+
+		if (!empty($nameSearchPattern)) {
+			$query->andWhere(
+				$query->expr()->like(
+					'name',
+					$query->expr()->literal('%' . $this->connection->escapeLikeParameter($nameSearchPattern). '%')
+				)
+			);
+		}
+
+		$query
+			->addOrderBy('name', 'ASC')
+			->addOrderBy('visibility', 'ASC')
+			->addOrderBy('editable', 'ASC');
+
+		$result = $query->execute();
+		while ($row = $result->fetch()) {
+			$tags[$row['id']] = $this->createSystemTagFromRow($row);
+		}
+
+		$result->closeCursor();
+
+		return $tags;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getTag($tagName, $userVisible, $userAssignable) {
+		$userVisible = (int)$userVisible;
+		$userAssignable = (int)$userAssignable;
+
+		$result = $this->selectTagQuery
+			->setParameter('name', $tagName)
+			->setParameter('visibility', $userVisible)
+			->setParameter('editable', $userAssignable)
+			->execute();
+
+		$row = $result->fetch();
+		$result->closeCursor();
+		if (!$row) {
+			throw new TagNotFoundException(
+				'Tag ("' . $tagName . '", '. $userVisible . ', ' . $userAssignable . ') does not exist'
+			);
+		}
+
+		return $this->createSystemTagFromRow($row);
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function createTag($tagName, $userVisible, $userAssignable) {
+		$userVisible = (int)$userVisible;
+		$userAssignable = (int)$userAssignable;
+
+		$query = $this->connection->getQueryBuilder();
+		$query->insert(self::TAG_TABLE)
+			->values([
+				'name' => $query->createNamedParameter($tagName),
+				'visibility' => $query->createNamedParameter($userVisible),
+				'editable' => $query->createNamedParameter($userAssignable),
+			]);
+
+		try {
+			$query->execute();
+		} catch (UniqueConstraintViolationException $e) {
+			throw new TagAlreadyExistsException(
+				'Tag ("' . $tagName . '", '. $userVisible . ', ' . $userAssignable . ') already exists',
+				0,
+				$e
+			);
+		}
+
+		$tagId = $this->connection->lastInsertId('*PREFIX*' . self::TAG_TABLE);
+
+		return new SystemTag(
+			(int)$tagId,
+			$tagName,
+			(bool)$userVisible,
+			(bool)$userAssignable
+		);
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function updateTag($tagId, $tagName, $userVisible, $userAssignable) {
+		$userVisible = (int)$userVisible;
+		$userAssignable = (int)$userAssignable;
+
+		$query = $this->connection->getQueryBuilder();
+		$query->update(self::TAG_TABLE)
+			->set('name', $query->createParameter('name'))
+			->set('visibility', $query->createParameter('visibility'))
+			->set('editable', $query->createParameter('editable'))
+			->where($query->expr()->eq('id', $query->createParameter('tagid')))
+			->setParameter('name', $tagName)
+			->setParameter('visibility', $userVisible)
+			->setParameter('editable', $userAssignable)
+			->setParameter('tagid', $tagId);
+
+		try {
+			if ($query->execute() === 0) {
+				throw new TagNotFoundException(
+					'Tag ("' . $tagName . '", '. $userVisible . ', ' . $userAssignable . ') does not exist'
+				);
+			}
+		} catch (UniqueConstraintViolationException $e) {
+			throw new TagAlreadyExistsException(
+				'Tag ("' . $tagName . '", '. $userVisible . ', ' . $userAssignable . ') already exists',
+				0,
+				$e
+			);
+		}
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function deleteTags($tagIds) {
+		if (!is_array($tagIds)) {
+			$tagIds = [$tagIds];
+		}
+
+		// delete relationships first
+		$query = $this->connection->getQueryBuilder();
+		$query->delete(SystemTagObjectMapper::RELATION_TABLE)
+			->where($query->expr()->in('systemtagid', $query->createParameter('tagids')))
+			->setParameter('tagids', $tagIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
+			->execute();
+
+		$query = $this->connection->getQueryBuilder();
+		$query->delete(self::TAG_TABLE)
+			->where($query->expr()->in('id', $query->createParameter('tagids')))
+			->setParameter('tagids', $tagIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY);
+
+		if ($query->execute() === 0) {
+			throw new TagNotFoundException(
+				'Tag does not exist'
+			);
+		}
+	}
+
+	private function createSystemTagFromRow($row) {
+		return new SystemTag((int)$row['id'], $row['name'], (bool)$row['visibility'], (bool)$row['editable']);
+	}
+}
diff --git a/lib/private/systemtag/systemtagobjectmapper.php b/lib/private/systemtag/systemtagobjectmapper.php
new file mode 100644
index 00000000000..f2adc2e3ebd
--- /dev/null
+++ b/lib/private/systemtag/systemtagobjectmapper.php
@@ -0,0 +1,213 @@
+<?php
+/**
+ * @author Vincent Petry <pvince81@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OC\SystemTag;
+
+use \OCP\SystemTag\ISystemTagManager;
+use \OCP\IDBConnection;
+use \OCP\SystemTag\TagNotFoundException;
+use \Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+
+class SystemTagObjectMapper implements \OCP\SystemTag\ISystemTagObjectMapper {
+
+	const RELATION_TABLE = 'systemtag_object_mapping';
+
+	/**
+	 * @var ISystemTagManager
+	 */
+	private $tagManager;
+
+	/**
+	 * @var IDBConnection
+	 */
+	private $connection;
+
+	/**
+	* Constructor.
+	*
+	* @param IDBConnection $connection database connection
+	* @param ISystemTagManager $tagManager system tag manager
+	*/
+	public function __construct(IDBConnection $connection, ISystemTagManager $tagManager) {
+		$this->connection = $connection;
+		$this->tagManager = $tagManager;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getTagIdsForObjects($objIds, $objectType) {
+		if (!is_array($objIds)) {
+			$objIds = [$objIds];
+		}
+
+		$query = $this->connection->getQueryBuilder();
+		$query->select(['systemtagid', 'objectid'])
+			->from(self::RELATION_TABLE)
+			->where($query->expr()->in('objectid', $query->createParameter('objectids')))
+			->andWhere($query->expr()->eq('objecttype', $query->createParameter('objecttype')))
+			->setParameter('objectids', $objIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
+			->setParameter('objecttype', $objectType)
+			->addOrderBy('objectid', 'ASC')
+			->addOrderBy('systemtagid', 'ASC');
+
+		$mapping = [];
+		foreach ($objIds as $objId) {
+			$mapping[$objId] = [];
+		}
+
+		$result = $query->execute();
+		while ($row = $result->fetch()) {
+			$objectId = $row['objectid'];
+			$mapping[$objectId][] = $row['systemtagid'];
+		}
+
+		$result->closeCursor();
+
+		return $mapping;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function getObjectIdsForTags($tagIds, $objectType) {
+		if (!is_array($tagIds)) {
+			$tagIds = [$tagIds];
+		}
+
+		$this->assertTagsExist($tagIds);
+
+		$query = $this->connection->getQueryBuilder();
+		$query->select($query->createFunction('DISTINCT(objectid)'))
+			->from(self::RELATION_TABLE)
+			->where($query->expr()->in('systemtagid', $query->createParameter('tagids')))
+			->andWhere($query->expr()->eq('objecttype', $query->createParameter('objecttype')))
+			->setParameter('tagids', $tagIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
+			->setParameter('objecttype', $objectType);
+
+		$objectIds = [];
+
+		$result = $query->execute();
+		while ($row = $result->fetch()) {
+			$objectIds[] = $row['objectid'];
+		}
+
+		return $objectIds;
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function assignTags($objId, $objectType, $tagIds) {
+		if (!is_array($tagIds)) {
+			$tagIds = [$tagIds];
+		}
+
+		$this->assertTagsExist($tagIds);
+
+		$query = $this->connection->getQueryBuilder();
+		$query->insert(self::RELATION_TABLE)
+			->values([
+				'objectid' => $query->createNamedParameter($objId),
+				'objecttype' => $query->createNamedParameter($objectType),
+				'systemtagid' => $query->createParameter('tagid'),
+			]);
+
+		foreach ($tagIds as $tagId) {
+			try {
+				$query->setParameter('tagid', $tagId);
+				$query->execute();
+			} catch (UniqueConstraintViolationException $e) {
+				// ignore existing relations
+			}
+		}
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function unassignTags($objId, $objectType, $tagIds) {
+		if (!is_array($tagIds)) {
+			$tagIds = [$tagIds];
+		}
+
+		$this->assertTagsExist($tagIds);
+
+		$query = $this->connection->getQueryBuilder();
+		$query->delete(self::RELATION_TABLE)
+			->where($query->expr()->eq('objectid', $query->createParameter('objectid')))
+			->andWhere($query->expr()->eq('objecttype', $query->createParameter('objecttype')))
+			->andWhere($query->expr()->in('systemtagid', $query->createParameter('tagids')))
+			->setParameter('objectid', $objId)
+			->setParameter('objecttype', $objectType)
+			->setParameter('tagids', $tagIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
+			->execute();
+	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function haveTag($objIds, $objectType, $tagId, $all = true) {
+		$this->assertTagsExist([$tagId]);
+
+		$query = $this->connection->getQueryBuilder();
+		$query->select($query->createFunction('COUNT(1)'))
+			->from(self::RELATION_TABLE)
+			->where($query->expr()->in('objectid', $query->createParameter('objectids')))
+			->andWhere($query->expr()->eq('objecttype', $query->createParameter('objecttype')))
+			->andWhere($query->expr()->eq('systemtagid', $query->createParameter('tagid')))
+			->setParameter('objectids', $objIds, \Doctrine\DBAL\Connection::PARAM_INT_ARRAY)
+			->setParameter('tagid', $tagId)
+			->setParameter('objecttype', $objectType)
+			->setMaxResults(1);
+
+		$result = $query->execute();
+		$row = $result->fetch(\PDO::FETCH_NUM);
+		$result->closeCursor();
+		if ($all) {
+			return ((int)$row[0] === count($objIds));
+		} else {
+			return (int)$row[0] > 0;
+		}
+	}
+
+	/**
+	 * Asserts that all the given tag ids exist.
+	 *
+	 * @param string[] $tagIds tag ids to check
+	 *
+	 * @throws \OCP\SystemTag\TagNotFoundException if at least one tag did not exist
+	 */
+	private function assertTagsExist($tagIds) {
+		$tags = $this->tagManager->getTagsById($tagIds);
+		if (count($tags) !== count($tagIds)) {
+			// at least one tag missing, bail out
+			$foundTagIds = array_map(
+				function($tag) {
+					return $tag->getId();
+				},
+				$tags
+			);
+			$missingTagIds = array_diff($tagIds, $foundTagIds);
+			throw new TagNotFoundException('Tags ' . json_encode($missingTagIds) . ' do not exist');
+		}
+	}
+}
diff --git a/lib/public/iservercontainer.php b/lib/public/iservercontainer.php
index d85f812b2e7..7cb2672254b 100644
--- a/lib/public/iservercontainer.php
+++ b/lib/public/iservercontainer.php
@@ -470,4 +470,22 @@ interface IServerContainer {
 	 * @since 8.2.0
 	 */
 	public function getNotificationManager();
+
+	/**
+	 * Returns the system-tag manager
+	 *
+	 * @return \OCP\SystemTag\ISystemTagManager
+	 *
+	 * @since 9.0.0
+	 */
+	public function getSystemTagManager();
+
+	/**
+	 * Returns the system-tag object mapper
+	 *
+	 * @return \OCP\SystemTag\ISystemTagObjectMapper
+	 *
+	 * @since 9.0.0
+	 */
+	public function getSystemTagObjectMapper();
 }
diff --git a/lib/public/systemtag/isystemtag.php b/lib/public/systemtag/isystemtag.php
index 76a812f38dc..26609fd8af7 100644
--- a/lib/public/systemtag/isystemtag.php
+++ b/lib/public/systemtag/isystemtag.php
@@ -62,7 +62,7 @@ interface ISystemTag {
 	 *
 	 * @since 9.0.0
 	 */
-	public function isUserAsssignable();
+	public function isUserAssignable();
 
 }
 
diff --git a/lib/public/systemtag/isystemtagsmanager.php b/lib/public/systemtag/isystemtagmanager.php
index df59cc48d52..2020ec52900 100644
--- a/lib/public/systemtag/isystemtagsmanager.php
+++ b/lib/public/systemtag/isystemtagmanager.php
@@ -31,9 +31,11 @@ interface ISystemTagManager {
 	/**
 	 * Returns the tag objects matching the given tag ids.
 	 *
-	 * @param array|string $tagIds The ID or array of IDs of the tags to retrieve
+	 * @param array|string $tagIds id or array of unique ids of the tag to retrieve
 	 *
-	 * @return \OCP\SystemTag\ISystemTag[] array of system tags or empty array if none found
+	 * @return \OCP\SystemTag\ISystemTag[] array of system tags with tag id as key
+	 *
+	 * @throws \OCP\SystemTag\TagNotFoundException if at least one given tag id did no exist
 	 *
 	 * @since 9.0.0
 	 */
@@ -72,14 +74,14 @@ interface ISystemTagManager {
 	/**
 	 * Returns all known tags, optionally filtered by visibility.
 	 *
-	 * @param bool $visibleOnly whether to only return user visible tags
+	 * @param bool|null $visibilityFilter filter by visibility if non-null
 	 * @param string $nameSearchPattern optional search pattern for the tag name
 	 *
 	 * @return \OCP\SystemTag\ISystemTag[] array of system tags or empty array if none found
 	 *
 	 * @since 9.0.0
 	 */
-	public function getAllTags($visibleOnly = false, $nameSearchPattern = null);
+	public function getAllTags($visibilityFilter = null, $nameSearchPattern = null);
 
 	/**
 	 * Updates the given tag
diff --git a/lib/public/systemtag/isystemtagobjectmapper.php b/lib/public/systemtag/isystemtagobjectmapper.php
index 8c6c27c4846..e2ac1fab124 100644
--- a/lib/public/systemtag/isystemtagobjectmapper.php
+++ b/lib/public/systemtag/isystemtagobjectmapper.php
@@ -69,6 +69,11 @@ interface ISystemTagObjectMapper {
 	/**
 	 * Assign the given tags to the given object.
 	 *
+	 * If at least one of the given tag ids doesn't exist, none of the tags
+	 * will be assigned.
+	 *
+	 * If the relationship already existed, fail silently.
+	 *
 	 * @param string $objId object id
 	 * @param string $objectType object type
 	 * @param string|array $tagIds tag id or array of tag ids to assign
@@ -83,6 +88,11 @@ interface ISystemTagObjectMapper {
 	/**
 	 * Unassign the given tags from the given object.
 	 *
+	 * If at least one of the given tag ids doesn't exist, none of the tags
+	 * will be unassigned.
+	 *
+	 * If the relationship did not exist in the first place, fail silently.
+	 *
 	 * @param string $objId object id
 	 * @param string $objectType object type
 	 * @param string|array $tagIds tag id or array of tag ids to unassign