Overridden `config.php` variables via `NC_*` cannot be arrays (or anything else than strings)

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

PR #3966 introduced the possibility to override values in config.php via environment variables (a feature frequently used in container setups).

However, they are always interpreted as raw strings so it doesn't work when e.g. arrays are expected for a given config key.

Steps to reproduce

1. Setup a NextCloud instance and define the environment variable NC_app_install_overwrite to htmlviewer epubviewer ncdownloader instead of config.php
2. Run occ config:system:get app_install_overwrite
3. The string htmlviewer epubviewer ncdownloader is returned and it's effectless because Nextcloud expects an array there when checking the app overrides.

Expected behavior

An array containing the values htmlviewer, epubviewer, and ncdownloader is returned.

Installation method

Community Docker image

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?

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

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

Configuration report

{
"system": {
+-- 97 lines: "version": "30.0.0.2",······························································································································································································································································································································································································································································································
}
}

List of activated Apps

Enabled:

• activity: 2.17.0
• admin_audit: 1.15.0
• audioplayer: 3.3.1
• bookmarks: 12.0.0
• bruteforcesettings: 2.5.0
• calendar: 4.2.1
• camerarawpreviews: 0.8.0
• circles: 25.0.0
• cloud_federation_api: 1.8.0
• cloud_py_api: 0.1.1
• comments: 1.15.0
• contacts: 5.0.2
• contactsinteraction: 1.6.0
• cookbook: 0.10.1
• cospend: 1.5.5
• dashboard: 7.5.0
• dav: 1.24.0
• deck: 1.8.3
• epubivewer: 1.6.7
• external: 5.0.0
• facerecognition: 0.9.11
• federatedfilesharing: 1.15.0
• federation: 1.15.0
• files: 1.20.1
• files_automatedtagging: 1.15.0
• files_downloadactivity: 1.15.0
• files_external: 1.17.0
• files_fulltextsearch: 25.0.0
• files_fulltextsearch_tesseract: 25.0.0
• files_linkeditor: 1.1.13
• files_mindmap: 0.0.27
• files_pdfviewer: 2.6.0
• files_rightclick: 1.4.0
• files_sharing: 1.17.0
• files_trashbin: 1.15.0
• files_versions: 1.18.0
• firstrunwizard: 2.14.0
• forms: 3.0.3
• fulltextsearch: 25.0.0
• fulltextsearch_elasticsearch: 25.0.0
• gpxpod: 5.0.4
• groupfolders: 13.1.0
• guests: 2.3.0
• health: 1.6.1
• htmlviewer: 29.2.0
• impersonate: 1.11.0
• logreader: 2.10.0
• lookup_server_connector: 1.13.0
• mail: 2.2.2
• maps: 0.2.4
• mediadc: 0.3.2
• metadata: 0.17.0
• music: 1.8.1
• ncdownloader: 1.0.21
• news: 20.0.0
• nextcloud_announcements: 1.14.0
• notes: 4.6.0
• notifications: 2.13.1
• notify_push: 0.5.0
• oauth2: 1.13.0
• onlyoffice: 7.6.8
• password_policy: 1.15.0
• phonetrack: 0.7.2
• photos: 2.0.1
• polls: 4.0.0
• previewgenerator: 5.1.1
• privacy: 1.9.0
• provisioning_api: 1.15.0
• quota_warning: 1.15.0
• recognize: 3.3.4
• recommendations: 1.4.0
• related_resources: 1.0.3
• serverinfo: 1.15.0
• settings: 1.7.0
• sharebymail: 1.15.0
• side_menu: 3.5.1
• socialsharing_email: 2.5.0
• spreed: 15.0.2
• support: 1.8.0
• survey_client: 1.13.0
• suspicious_login: 4.3.0
• systemtags: 1.15.0
• tasks: 0.14.5
• text: 3.6.0
• theming: 2.0.1
• twofactor_backupcodes: 1.14.0
• twofactor_email: 2.7.1
• twofactor_gateway: 0.20.0
• twofactor_totp: 7.0.0
• twofactor_webauthn: 1.0.0
• unsplash: 2.1.1
• updatenotification: 1.15.0
• user_status: 1.5.0
• viewer: 1.9.0
• weather_status: 1.5.0
• workflowengine: 2.7.0
  Disabled:
• encryption: 2.2.0
• files_accesscontrol: 1.15.1
• files_markdown: 2.3.6
• user_ldap: 1.14.1
• user_saml: 5.1.2

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start by tracing the environment-variable override introduced in PR #3966 and the occ config:system:get entry point. Reproduce the NC_app_install_overwrite case and verify that the command returns htmlviewer, epubviewer, and ncdownloader as an array while string-valued overrides continue to work.