linux Desktop App 6.x selective sync not working for subfolders of already synchronized paths #12465

Pre-submission Checks

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Describe the bug

Using selective sync, folders and a files at a certain depth are
synchronized the first time the folder is choosen,
but adding a synchronization of a subfolder to an already synchronized
path does not work.
Nothing in logs in both client and server, and force sync does not trigger any action.

Expected behavior

Folders checked/unchecked in the client should be synchronized,
in particular subfolders of already synchronized folders that might
have been excluded earlier

Steps to reproduce the issue

1. Create a folder sync based on the root of the server, but then exclude all folders but one with at least depth 3.

Example:

owncloud -> folderA -> folderA.1

2. Let the app synchronize. Then :

3. In the OwnCloud desktop client navigate to a synchronization, click the three dots, select “choose what to sync” and tick a folder inside folderA to be syncronized, click on “Ok”

example

owncloud -> folderA -> folderA.2

4. Wait for the client to sync. Despite all being green, the folder folderA.2 is not synchronized.

5. Click on "force synchronization" - nothing happens

6. repeat step 1-6 with another folder B, never synchronized, first choose owncloud -> FolderB -> folderB.1 , let it synchronize and then later pick owncloud -> FolderB -> FolderB.2. FolderB.2 is not synchronized

In practice the first time a completely new path is chosen to be synchronized, synchronization occurs,
but adding a subfolder to an already synchronized path does not work.

Restarting the client doesn't help.

I did not try with other versions of the client but I am going to revert to
the latest 5.x and add findings to this issue.

I can reproduce all times.

Screenshots

No response

Logs

I do not attach the logs due to sensitive information, but nothing is logged
about the choice of a new subfolder folderA.2 or folderB.2 both in the client and on the server. The folders are checked properly in the graphical interface, so at least the GUI knows what to sync, but the synchronization layer does not do anything. I should look at the DB maybe.

I can create a test user with less sensitive information if more input in form of logs is required.

Client version number

Client version: 6.0.3.18040
OS language: English
Qt version 6.8.3
Openssl 3.4.3
Installation path of client: defaults

The about dialog says: using virtual files plugin: suffix
I did not enable virtual files support.

Desktop environment (Linux only)

Ubuntu 24.04 with Gnome3, 6.17.0-14-generic #14~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Jan 15 15:52:10 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Client package version and origin (Linux only)

Installed from https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/download/

Installation path (Windows only)

No response

Server information

Official Docker Image for community edition
ownCloud version: 10.16
Operating system: Alma Linux 9.x
Web server: Apache (official owncloud docker image)
Database: mariadb (official owncloud docker image)
PHP version: version in official owncloud docker image
Storage backend (external storage): none, using mounted local disk

Additional context

I experienced this behavior since version 6.x of the Desktop App. I did not try reverting to version 5.x yet.

All folders and subfolders added during the first installation/configuration continue to sync regularly so far. It's the code that handles changes what to synchronize ("Choose what to sync") that seems not to work.

The GUI remembers selected folders properly (i.e. database and configuration seems to be correct). The problem is in the app logic with selective syncronization somewhere else.