(WIP) Attempt to fix hard upload failures during quota events

[joshtrichards]

This is an attempt to fix a backend fail triggered by quota issues while uploading.

• Related to: [Bug]: When uploading a file from browser or windows desktop app, it give following error getUploadStorage(): Argument #1 ($targetPath) must be of type string, null given nextcloud/server#37578

Summary

I discovered this while trying to reproduce nextcloud#37578. Technically this may fix that issue as well (it's the same call/code path with a null parameter), but I was only able to reproduce the issue reported there under one condition: if upload would cause the user quota to be exceeded.

In the course of looking into the issue I could reproduce, I came up with this "fix". This area of code is not one I was at all
familiar with previously so I can't say I'd even give a "LGTM" even though I'm the one submitting it. There is an issue, but the best fix may me a variation.

In prepareUpload() the $request->getPath() will contain something like:

• w/o dirname: uploads/ncadmin/web-file-upload-464f2b6a78f780318dc46e3424dbc0fc-1680893450217 (note it doesn't have the chunk # unlike beforePut())
• w/ dirname: uploads/ncadmin

Currently we pass the whole thing (1st one) here to prepareUpload() which fails under at least one confirmed scenario (quota exceeded situations).

Without this patch, uploads fail in an ugly way on the backend when the quota is exceeded:

TypeError: OCA\DAV\Upload\ChunkingV2Plugin::getUploadStorage(): Argument #1 ($targetPath) must be of type string, null given, called in /var/www/html/apps/dav/lib/Upload/ChunkingV2Plugin.php on line 285

This is not an issue if the quota isn't triggered. Though, interestingly, $uploadMetadata is always blank

As far as I can tell $uploadMetadata is always null.

---

uploadPath gets set in prepareUpload()
It gets set to either:
$uploadMetadata[self::UPLOAD_TARGET_PATH] or null

checkPrerequisuites() is called by beforePut() + beforeMove
But not by beforeDelete()
Among other things it checks if uploadPath is null
and throws a PreconditionFailed exception if so:
"Missing metadata for chunked upload"

Since checkPrerequisites() is never called in beforeDelete()...
beforeDelete() happily calls getUploadStorage() with a null...
uploadPath

Observations:

The main way uploadPath ends up null is...
...if $uploadMetadata[self::UPLOAD_TARGET_PATH] isn't set...
...in prepareUpload()...
...which gets $uploadMetadata via...
$this->cache->get($this->uploadFolder->getName());

---

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)