[Bug]: Shared Collectives cause "Path not found" when scannig files with "occ files:scan --all"

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When a Collective is shared with one or more users and you start a manual file scan using occ files:scan --all, this leads to the following error message for each user who is member of a Collective circle:

Path not found: /username

Where username is the name of the affected user.

Steps to reproduce

1. Create a collective
2. Share it with at least one other user
3. Run occ files:scan --all in a terminal

Expected behavior

occ files:scan --all runs without "Path not found" error messages

Installation method

Community Manual installation with Archive

Nextcloud Server version

28

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.1

Web server

Apache (supported)

Database engine version

MariaDB

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

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

There is a workaround to fix this. In /server/lib/private/Files/Utils/Scanner.php the following code needs to be added, so Collectives mounts will be ignored during a file scan:

            // don't scan received local shares, these can be scanned when scanning the owner's storage
            if ($storage->instanceOfStorage(SharedStorage::class)
                || $storage->instanceOfStorage(CollectiveStorage::class)
            ) {
                continue;
            }

Also see https://help.nextcloud.com/t/occ-files-scan-outputs-path-not-found-for-some-users/177507/12 and https://github.com/nextcloud/server/blob/5125c34f011651821d3a1d6e3ce2d0337ab75fe9/lib/private/Files/Utils/Scanner.php#L237-L239

Start in lib/private/Files/Utils/Scanner.php and reproduce the issue with occ files:scan --all after sharing a Collective. Review the existing handling for SharedStorage and the reported CollectiveStorage workaround. Done means the scan completes without Path not found errors for users in Collective circles.