Server: Error: undefined variable $response in DAV storage

[ChristophWurst]

Steps to reproduce

1. Call https://github.com/nextcloud/server/blob/8601bbc35d915d6dc1c847560d148981c518c27f/lib/private/Files/Storage/DAV.php#L829
2. Hit https://github.com/nextcloud/server/blob/master/lib/private/Files/Storage/DAV.php#L855
3. Hit https://github.com/nextcloud/server/blob/8601bbc35d915d6dc1c847560d148981c518c27f/lib/private/Files/Storage/DAV.php#L283

Expected behaviour

Condition is detected and handled (logged, ignored).

Actual behaviour

An unexpected condition is met and a non-existent variable is accessed.

Ref https://sentry.rullzer.com/sentry/nextcloud/issues/150 (for people with access).

[nextcloud-bot]

GitMate.io thinks possibly related issues are https://github.com/nextcloud/server/issues/4730 (Storage), https://github.com/nextcloud/server/issues/10665 (DAV Error in Nextcloud 14), https://github.com/nextcloud/server/pull/10417 (Fix undefined constant error for STATUS_SERVICE_UNAVAILABLE), https://github.com/nextcloud/server/issues/5684 (Error Message "undefined offset" with comments), and https://github.com/nextcloud/server/issues/9784 (Undefined index: {DAV:}getlastmodified at /var/www/html/lib/private/Files/Storage/DAV.php#582).

[ChristophWurst]

@nextcloud-bot nope, not even close …

[skjnldsv]

Still relevant @ChristophWurst ?

[kesselb]

Yes. See https://github.com/nextcloud/server/issues/16471 for example. We should not reach return $response if undefined.

[skjnldsv]

Nice!
So duplicate or relevant of #16471 @kesselb ?

[kesselb]

Relevant but not a duplicate. #16471 is running into the undefined return but the problem is with sabre/dav or alfresco. This issue is about the incomplete error handling.