[Bug]: 'Invalid storage backend "smb"' when only smbclient is installed

[jplitza]

⚠️ 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 having only the smbclient binary installed (not php-smbclient, which should be enough according to the docs), adding an external storage of type smb will fail.

Steps to reproduce

1. Install Nextcloud
2. Install files_external app
3. Install smbclient binary
4. Configure external storage of type smb (details don't matter)

Expected behavior

The storage is created and a connection is attempted.

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MySQL

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

Fresh Nextcloud Server install

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

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

#52681 introduced "optional" dependencies, but didn't add support for them here:

server/apps/files_external/lib/Controller/StoragesController.php

Lines 143 to 153 in 51a0943

	if ($backend->checkDependencies()) {
	// invalid backend
	return new DataResponse(
	[
	'message' => $this->l10n->t('Invalid storage backend "%s"', [
	$backend->getIdentifier(),
	]),
	],
	Http::STATUS_UNPROCESSABLE_ENTITY
	);
	}