Add Transactional trait for atomic DB operations

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

lib/composer/composer/autoload_classmap.php

@@ -35,6 +35,7 @@ return array(
     'OCP\\AppFramework\\Db\\Mapper' => $baseDir . '/lib/public/AppFramework/Db/Mapper.php',
     'OCP\\AppFramework\\Db\\MultipleObjectsReturnedException' => $baseDir . '/lib/public/AppFramework/Db/MultipleObjectsReturnedException.php',
     'OCP\\AppFramework\\Db\\QBMapper' => $baseDir . '/lib/public/AppFramework/Db/QBMapper.php',
+    'OCP\\AppFramework\\Db\\TTransactional' => $baseDir . '/lib/public/AppFramework/Db/TTransactional.php',
     'OCP\\AppFramework\\Http' => $baseDir . '/lib/public/AppFramework/Http.php',
     'OCP\\AppFramework\\Http\\ContentSecurityPolicy' => $baseDir . '/lib/public/AppFramework/Http/ContentSecurityPolicy.php',
     'OCP\\AppFramework\\Http\\DataDisplayResponse' => $baseDir . '/lib/public/AppFramework/Http/DataDisplayResponse.php',

lib/composer/composer/autoload_static.php

@@ -64,6 +64,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OCP\\AppFramework\\Db\\Mapper' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Db/Mapper.php',
         'OCP\\AppFramework\\Db\\MultipleObjectsReturnedException' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Db/MultipleObjectsReturnedException.php',
         'OCP\\AppFramework\\Db\\QBMapper' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Db/QBMapper.php',
+        'OCP\\AppFramework\\Db\\TTransactional' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Db/TTransactional.php',
         'OCP\\AppFramework\\Http' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Http.php',
         'OCP\\AppFramework\\Http\\ContentSecurityPolicy' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Http/ContentSecurityPolicy.php',
         'OCP\\AppFramework\\Http\\DataDisplayResponse' => __DIR__ . '/../../..' . '/lib/public/AppFramework/Http/DataDisplayResponse.php',

lib/public/AppFramework/Db/TTransactional.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2022 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2022 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCP\AppFramework\Db;
+
+use OCP\DB\Exception;
+use OCP\IDBConnection;
+use Throwable;
+
+/**
+ * Helper trait for transactional operations
+ *
+ * @since 24.0.0
+ */
+trait TTransactional {
+
+	/**
+	 * Run an atomic database operation
+	 *
+	 * - Commit if no exceptions are thrown, return the callable result
+	 * - Revert otherwise and rethrows the exception
+	 *
+	 * @template T
+	 * @param callable $fn
+	 * @psalm-param callable():T $fn
+	 * @param IDBConnection $db
+	 *
+	 * @return mixed the result of the passed callable
+	 * @psalm-return T
+	 *
+	 * @throws Exception for possible errors of commit or rollback or the custom operations within the closure
+	 * @throws Throwable any other error caused by the closure
+	 *
+	 * @since 24.0.0
+	 * @see https://docs.nextcloud.com/server/latest/developer_manual/basics/storage/database.html#transactions
+	 */
+	protected function atomic(callable $fn, IDBConnection $db) {
+		$db->beginTransaction();
+		try {
+			$result = $fn();
+			$db->commit();
+			return $result;
+		} catch (Throwable $e) {
+			$db->rollBack();
+			throw $e;
+		}
+	}
+}

tests/lib/AppFramework/Db/TransactionalTest.php

@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+/*
+ * @copyright 2022 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2022 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace lib\AppFramework\Db;
+
+use OCP\AppFramework\Db\TTransactional;
+use OCP\IDBConnection;
+use PHPUnit\Framework\MockObject\MockObject;
+use RuntimeException;
+use Test\TestCase;
+
+class TransactionalTest extends TestCase {
+
+	/** @var IDBConnection|MockObject */
+	private IDBConnection $db;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->db = $this->createMock(IDBConnection::class);
+	}
+
+	public function testAtomicRollback(): void {
+		$test = new class($this->db) {
+			use TTransactional;
+
+			private IDBConnection $db;
+
+			public function __construct(IDBConnection $db) {
+				$this->db = $db;
+			}
+
+			public function fail(): void {
+				$this->atomic(function () {
+					throw new RuntimeException('nope');
+				}, $this->db);
+			}
+		};
+		$this->db->expects(self::once())
+			->method('beginTransaction');
+		$this->db->expects(self::once())
+			->method('rollback');
+		$this->db->expects(self::never())
+			->method('commit');
+		$this->expectException(RuntimeException::class);
+
+		$test->fail();
+	}
+
+	public function testAtomicCommit(): void {
+		$test = new class($this->db) {
+			use TTransactional;
+
+			private IDBConnection $db;
+
+			public function __construct(IDBConnection $db) {
+				$this->db = $db;
+			}
+
+			public function succeed(): int {
+				return $this->atomic(function () {
+					return 3;
+				}, $this->db);
+			}
+		};
+		$this->db->expects(self::once())
+			->method('beginTransaction');
+		$this->db->expects(self::never())
+			->method('rollback');
+		$this->db->expects(self::once())
+			->method('commit');
+
+		$result = $test->succeed();
+
+		self::assertEquals(3, $result);
+	}
+}