[5.9] _subfolder() and _cfPrefix() pass null to rtrim() when env var resolves to empty string

[mtwalsh]

Description

Fs::_subfolder() and Fs::_cfPrefix() call Craft::parseEnv() and pass the result directly to rtrim(). When the referenced environment variable resolves to an empty string, App::parseEnv() returns null (by design — see App::parseEnv() lines 240–241), causing a PHP TypeError:

TypeError: rtrim(): Argument #1 ($string) must be of type string, null given

The issue is on line 509 of src/Fs.php:

private function _subfolder(): string
{
    if ($this->subfolder && ($subfolder = rtrim(Craft::parseEnv($this->subfolder), '/')) !== '') {
        return $subfolder . '/';
    }
    return '';
}

When subfolder is set to an env var reference (e.g. $MY_SUBFOLDER) in project config, $this->subfolder is the raw string $MY_SUBFOLDER (truthy), so it enters the if branch. Craft::parseEnv('$MY_SUBFOLDER') resolves the env var to "", which parseEnv() converts to null. Then rtrim(null, '/') throws.

The same pattern exists in _cfPrefix() on line 536.

A null-safe fix would be:

if ($this->subfolder && ($subfolder = rtrim(Craft::parseEnv($this->subfolder) ?? '', '/')) !== '') {

Steps to reproduce

1. Configure an S3 filesystem with subfolder: $MY_SUBFOLDER in project config
2. Set MY_SUBFOLDER="" in .env
3. Load any page that generates an asset URL from that filesystem

Additional info

• Craft version: 5.9.8
• PHP version: 8.2.30
• Database driver & version: N/A
• Plugins & versions: craftcms/aws-s3 2.2.4

[linear]

PT-3037

[brandonkelly]

Thanks for reporting that! v2.2.6 is out with a fix.