Add our own DB exception abstraction

Right now our API exports the Doctrine/dbal exception. As we've seen
with the dbal 3 upgrade, the leakage of 3rdparty types is problematic as
a dependency update means lots of work in apps, due to the direct
dependency of what Nextcloud ships. This breaks this dependency so that
apps only need to depend on our public API. That API can then be vendor
(db lib) agnostic and we can work around future deprecations/removals in
dbal more easily.

Right now the type of exception thrown is transported as "reason". For
the more popular types of errors we can extend the new exception class
and allow apps to catch specific errors only. Right now they have to
catch-check-rethrow. This is not ideal, but better than the dependnecy
on dbal.

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

1 files changed, 136 insertions, 0 deletions

diff --git a/lib/private/DB/Exceptions/DbalException.php b/lib/private/DB/Exceptions/DbalException.php
new file mode 100644
index 00000000000..4e0e1517048
--- /dev/null
+++ b/lib/private/DB/Exceptions/DbalException.php
@@ -0,0 +1,136 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * @copyright 2021 Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * @author 2021 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 OC\DB\Exceptions;
+
+use Doctrine\DBAL\ConnectionException;
+use Doctrine\DBAL\Exception\ConstraintViolationException;
+use Doctrine\DBAL\Exception\DatabaseObjectExistsException;
+use Doctrine\DBAL\Exception\DatabaseObjectNotFoundException;
+use Doctrine\DBAL\Exception\DeadlockException;
+use Doctrine\DBAL\Exception\DriverException;
+use Doctrine\DBAL\Exception\ForeignKeyConstraintViolationException;
+use Doctrine\DBAL\Exception\InvalidArgumentException;
+use Doctrine\DBAL\Exception\InvalidFieldNameException;
+use Doctrine\DBAL\Exception\NonUniqueFieldNameException;
+use Doctrine\DBAL\Exception\NotNullConstraintViolationException;
+use Doctrine\DBAL\Exception\ServerException;
+use Doctrine\DBAL\Exception\SyntaxErrorException;
+use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
+use OCP\DB\Exception;
+
+/**
+ * Wrapper around the raw dbal exception, so we can pass it to apps that catch
+ * our OCP db exception
+ *
+ * @psalm-immutable
+ */
+class DbalException extends Exception {
+
+	/** @var \Doctrine\DBAL\Exception */
+	private $original;
+
+	/**
+	 * @param \Doctrine\DBAL\Exception $original
+	 * @param int $code
+	 * @param string $message
+	 */
+	private function __construct(\Doctrine\DBAL\Exception $original, int $code, string $message) {
+		parent::__construct(
+			$message,
+			$code,
+			$original
+		);
+		$this->original = $original;
+	}
+
+	public static function wrap(\Doctrine\DBAL\Exception $original, string $message = ''): self {
+		return new self(
+			$original,
+			is_int($original->getCode()) ? $original->getCode() : 0,
+			empty($message) ? $original->getMessage() : $message
+		);
+	}
+
+	public function getReason(): ?int {
+		/**
+		 * Generic errors
+		 */
+		if ($this->original instanceof ConnectionException) {
+			return parent::REASON_CONNECTION_LOST;
+		}
+		if ($this->original instanceof DriverException) {
+			return parent::REASON_DRIVER;
+		}
+		if ($this->original instanceof InvalidArgumentException) {
+			return parent::REASON_INVALID_ARGUMENT;
+		}
+
+		/**
+		 * Constraint errors
+		 */
+		if ($this->original instanceof ForeignKeyConstraintViolationException) {
+			return parent::REASON_FOREIGN_KEY_VIOLATION;
+		}
+		if ($this->original instanceof NotNullConstraintViolationException) {
+			return parent::REASON_NOT_NULL_CONSTRAINT_VIOLATION;
+		}
+		if ($this->original instanceof UniqueConstraintViolationException) {
+			return parent::REASON_UNIQUE_CONSTRAINT_VIOLATION;
+		}
+		// The base exception comes last
+		if ($this->original instanceof ConstraintViolationException) {
+			return parent::REASON_CONSTRAINT_VIOLATION;
+		}
+
+		/**
+		 * Other server errors
+		 */
+		if ($this->original instanceof DatabaseObjectExistsException) {
+			return parent::REASON_DATABASE_OBJECT_EXISTS;
+		}
+		if ($this->original instanceof DatabaseObjectNotFoundException) {
+			return parent::REASON_DATABASE_OBJECT_NOT_FOUND;
+		}
+		if ($this->original instanceof DeadlockException) {
+			return parent::REASON_DEADLOCK;
+		}
+		if ($this->original instanceof InvalidFieldNameException) {
+			return parent::REASON_INVALID_FIELD_NAME;
+		}
+		if ($this->original instanceof NonUniqueFieldNameException) {
+			return parent::REASON_NON_UNIQUE_FIELD_NAME;
+		}
+		if ($this->original instanceof SyntaxErrorException) {
+			return parent::REASON_SYNTAX_ERROR;
+		}
+		// The base server exception class comes last
+		if ($this->original instanceof ServerException) {
+			return parent::REASON_SERVER;
+		}
+
+		return null;
+	}
+}