[Bug]: Removing a directory containing directory junction results in data loss

[Amunak]

Bug description

Removing a synced directory that contains a directory junction recursively deletes content within that directory junction, resulting in file removal (data loss) outside the Nextcloud-managed (synced) folder.

I feel like #4232 should be a much higher priority.

Steps to reproduce

1. Have a directory structure with valuable data somewhere on your PC and create an NTFS Directory Junction in your Nextcloud folder:

D:
|-data
| `-subfolder
|   `-valuable data.txt
`-Nextcloud
  `-whatever
    `-junction to D-data

2. Wait for it to sync and observe that the junction is (correctly) not synced, so on a synced system or web only an empty folder whatever/ exists. This to me indicates that Nextcloud knows it's a junction and doesn't want to touch it, which is intuitive and expected.
3. On a different synced system or from Nexctcloud FIles on Web remove folder whatever.
4. Observe that folder D:\\Nextcloud\\whatever correctly disappeared. More importantly observe that D:\\data\\subfolder disappeared as well, and that your valuable data are gone.

Expected behavior

The directory junction should be removed (unlinked), but the data inside must not be deleted.

Alternatively not deleting the junction or the parent folder and only emitting an error and not syncing the parent folder would be acceptable as well.

Which files are affected by this bug

whatever

Operating system

Windows

Which version of the operating system you are running.

Windows 10

Package

Official install

Nextcloud Server version

23.0.5

Nextcloud Desktop Client version

3.5.2

Is this bug present after an update or on a fresh install?

Updated to a major version (ex. 3.3.6 to 3.4.0)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend

[Rello]

Hello,

thank you for reporting this issue.

This issue was reported long time ago on old versions and we improved a lot since then.
If the error shows up again, please open an issue for the current versions.

[Amunak]

Sooo you created an automated test for this to make sure it'll never happen again, right?

...right??

[plauderer]

another issue with junction points have been posted at #7157
A confirmation that the issue in #4770 was resolved would be nice!

[gerroon]

NC didn't use to sync Windows junction folders, which I liked a lot. Did this behavior change? It looks like it is synching them now and this should be optional given it changed an existing behavior. I am using client 3.14.1

[CorneliousJD]

Yes, #7157 is indeed a junction issue again - specifically inside the "Documents" folder there's "My Pictures" and "My Videos" and "My Music" junctions that are causing data loss too -- I am a victim of this and family photos have been lost now, thankfully I do have some backups but this is a very disastrous issue right now

[tairabiteru]

Issue is also present in 3.15.0.