DAV based `SEARCH` in a subfolder of a groupfolder does not return results

⚠️ 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

Involved app: groupfolders:
https://apps.nextcloud.com/apps/groupfolders

Searching in a sub folder of a group folder (/files/user/a_groupfolder/a_subfolder) does not return any results, although files are available there,

         <d:from>
             <d:scope>
                 <d:href>/files/user/a_groupfolder/a_subfolder</d:href>
                 <d:depth>0</d:depth>
             </d:scope>
         </d:from>

but when searching directly in the group folder (/files/user/a_groupfolder), files from a_groupfolder/a_subfolder are found.

         <d:from>
             <d:scope>
                 <d:href>/files/user/a_groupfolder</d:href>
                 <d:depth>0</d:depth>
             </d:scope>
         </d:from>

This only happens in groupfolders, files in sub folders of shared folders or normal user folders are found.

Steps to reproduce

Curl-Session:

curl -u user:pw 'https://server.org/remote.php/dav/' -X SEARCH -H "content-Type: text/xml" --data '<?xml version="1.0" encoding="UTF-8"?>
 <d:searchrequest xmlns:d="DAV:" xmlns:oc="http://owncloud.org/ns">
     <d:basicsearch>
         <d:select>
             <d:prop>
                 <oc:fileid/>
                 <d:displayname/>
                 <d:getcontenttype/>
                 <d:getetag/>
                 <oc:size/>
             </d:prop>
         </d:select>
         <d:from>
             <d:scope>
                 <d:href>/files/user/a_groupfolder/a_subfolder</d:href>
                 <d:depth>0</d:depth>
             </d:scope>
         </d:from>
         <d:where>
            <d:like>
                <d:prop>
                    <d:displayname/>
                </d:prop>
                <d:literal>%filepartname%</d:literal>
            </d:like>
         </d:where>
         <d:orderby/>
    </d:basicsearch>
</d:searchrequest>'

Result (empty):

<?xml version="1.0"?>
<d:multistatus xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns" xmlns:oc="http://owncloud.org/ns" xmlns:nc="http://nextcloud.org/ns"/>

Expected behavior

An XML response with the existing files in the sub folder of the group folder.

Installation method

None

Nextcloud Server version

26

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

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

None

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

No response

Start by reproducing the DAV SEARCH request through remote.php/dav against a groupfolder root and its subfolder, comparing the returned paths. Trace the groupfolders handling of scoped searches and compare it with normal and shared folders; done means the subfolder request returns an XML response containing the existing matching files.