symfony/translation · error · InvalidArgumentException

The translation provider DSN must contain a host (use…

Error message

The translation provider DSN must contain a host (use "default" by default).

What it means

Dsn requires a host component after scheme validation. Without a host the factory cannot target the provider API, so InvalidArgumentException is thrown; the message hints that "default" may be used where a provider accepts it.

Solutions

1. Add the provider's host to the DSN: 'scheme://key@host'.
2. Use 'default' as the host when the provider factory supports it (e.g. 'loco://KEY@default').
3. Check the env var/config for a truncated value (commonly missing after '@').
4. Look up the correct host in the provider factory's docs or tests for the scheme you use.

Example fix

// before
new Dsn('loco://API_KEY@');

// after
new Dsn('loco://API_KEY@default');

$params = parse_url($dsn);
if (!isset($params['host']) || '' === $params['host']) {
    throw new \InvalidArgumentException('DSN must include a host (use "default" if supported)');
}

try {
    $dsn = new Dsn($rawDsn);
} catch (\InvalidArgumentException $e) {
    // append the provider host or 'default' before retrying
}

When it happens

Trigger: new Dsn('loco://key@') or DSNs ending right after credentials with no host, e.g. 'scheme://user:pass@' or a truncated DSN in an env var.

Common situations: Templated DSN where the host variable was empty, cutting the string at '@' when copying credentials, or writing 'loco://key' assuming a default host exists for every provider.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

• The translation provider DSN is invalid.
• The translation provider DSN must contain a scheme.
• User is not set.
• Password is not set.
• Missing required option

AI-assisted analysis of symfony/translation@ae9e8a51bc (2026-09-15). Data as JSON: /api/errors/89736976fdb23321. Report an issue: GitHub.

Appendix: source

Thrown at Provider/Dsn.php:46

    private ?string $path;
    private array $options = [];
    private string $originalDsn;

    public function __construct(#[\SensitiveParameter] string $dsn)
    {
        $this->originalDsn = $dsn;

        if (false === $params = parse_url($dsn)) {
            throw new InvalidArgumentException('The translation provider DSN is invalid.');
        }

        if (!isset($params['scheme'])) {
            throw new InvalidArgumentException('The translation provider DSN must contain a scheme.');
        }
        $this->scheme = $params['scheme'];

        if (!isset($params['host'])) {
            throw new InvalidArgumentException('The translation provider DSN must contain a host (use "default" by default).');
        }
        $this->host = $params['host'];

        $this->user = '' !== ($params['user'] ?? '') ? rawurldecode($params['user']) : null;
        $this->password = '' !== ($params['pass'] ?? '') ? rawurldecode($params['pass']) : null;
        $this->port = $params['port'] ?? null;
        $this->path = $params['path'] ?? null;
        parse_str($params['query'] ?? '', $this->options);
    }

    public function getScheme(): string
    {
        return $this->scheme;
    }

    public function getHost(): string
    {
        return $this->host;

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