Files in a symlinked folder get deleted

[dadosch]

Expected behaviour

The files should not be deleted, as they are outside the synced folder.

Actual behaviour

They get deleted.

Steps to reproduce

1. create a folder in Nextcloud, say "folder", and "folder/example"
2. create a sync for that folder to a local folder, say "Nextcloud/folder"
3. (you might want to add some files to test it)
4. create a symlink from a local folder to "Nextcloud/folder/example".
5. (add some files again)
6. Delete "folder/example" in Nextcloud
7. Symlinked folder content gets deleted as well.

Client configuration

Client version: git 56c905, 2.5.2git

Operating system: Arch linux

OS language: German

Qt version used by client package (Linux only, see also Settings dialog): 5.12.3

Client package (From Nextcloud or distro) (Linux only): Distro

[Gigadoc2]

I can confirm this with 2.6.2.

With the risk of sounding entitled, I think this issue should be higher priority, as it can cause data loss: As the sync client does not follow symlinks when adding files, but does so when deleting them, there is plenty of opportunity to accidentially delete data.
One scenario could be that the user does not realize the synchronized folder contains symlinks, and as none of the linked files/folders are uploaded, they also don't show up in the web interface. If the user later deletes the synchronized folder in the web interface, they probably expect only those files listed in the webinterface to also be deleted from synchronized clients. They probably don't expect that the deletion will extend to files which are not listed in the web interface.
Another scenario (which would be me 😇) is that the user uses symlinks to deliberately exclude subfolders from synchronization, for example to link from a synchronized folder with report documents to a related git repository (the git repo is already "synchronized" in a different way, and synchronizing a git folder via nextcloud takes a long time). Now when the synchronized folder is removed for some reason, the linked to git project gets deleted as well, which is not the intended outcome.

To make things worse, if you periodically "backup" synchronized folders to limit the damage caused by a sync gone wrong, the usual tools (e.g cp) do not follow symlinks themselves, but copy them as is, so the folders affected by this behavior are not even included in your backup. In general, it is not the expected behavior of any application to follow symlinks when deleting.

Right now it seems that users should avoid using any symlinks at all inside the synchronized folders.

[vtronko]

I see a confirmation dialog, asking whether or not do I agree with deletion of local files, so nothing happens subtly.

[dadosch]

I see a confirmation dialog, asking whether or not do I agree with deletion of local files, so nothing happens subtly.

Well, the default behaviour of rm is not to follow symlinks, so one can assume that the sync client behaves similar. Also you expect nextcloud only to delete files which are indeed in the cloud not outside of the sync folder (and syncing a simlink currenly doesn't sync the contents, as @Gigadoc2 wrote).

[vtronko]

create a sync for that folder to a local folder, say "Nextcloud/folder"
create a symlink from a local folder to "Nextcloud/folder/example".

So you have a following structure:

.
└── Nextcloud
   └── folder (this folder right here is supposed to be synced with remote folder on server)
      ├── example
      └── symlink_to_example -> example

Delete "folder/example"

I don't see what is a problem here, both symlink and the content it is linking to are supposed to be deleted. Even without all the synchronization thing, if I remove the same folder locally, the same behavior happens, I have an empty Nextcloud folder in the end.

It looks confusing to me, can you please elaborate what exactly is wrong in my understanding?

[Gigadoc2]

@vtronko: It becomes a problem once symlinks point outside of the synchronized folder. Think of a structure like this:

.
├── External
│   └── example
│       └── data
└── Nextcloud
    └── folder (still the folder to be synced)
        └── example -> ../../External/example

If you now remove "folder" via Nextcloud, "data" gets deleted as well.

[github-actions]

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[github-actions]

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[Gigadoc2]

The behaviour has indeed changed now, but maybe not for the better: The Nextcloud client now gets stuck in this situation. After restarting it manually, it seems to delete everyting as appropriate, except for the symlink itself (which is perfectly acceptable considering that Nextcloud also does not sync symlinks). Just the getting stuck part is probably not intended.

[FlexW]

@Gigadoc2 thank you for your reply. Could you open up a ticket for that? So that we can better track the remaining issue?