What causes "Unable to load file "%s"." in symfony/translation?

Open the YAML file and make its top level a mapping (key: value lines) instead of a scalar.

symfony/translation · error · InvalidResourceException

Unable to load file " ".

Error message

Unable to load file "%s".

What it means

Thrown by the YamlFileLoader (translation resource loader) as an InvalidResourceException when a YAML translation file parses to valid YAML but the top-level value is not an array (it is a non-null scalar, e.g. a string or number). Translation catalogues must be mappings of message keys to translations, so any other top-level shape cannot be loaded.

Solutions

Open the YAML file and make its top level a mapping (key: value lines) instead of a scalar.
Check for accidental edits/merges that flattened the file structure.
Verify the file registered as a translation resource is actually a translation catalogue file.
Run `php -r "var_dump((new Symfony\Component\Yaml\Parser())->parseFile('messages.yaml', Yaml::PARSE_CONSTANT));"` to confirm the parsed root is an array.

Example fix

// before (messages.yaml)
translations

// after (messages.yaml)
hello: Hello
bye: Goodbye

Defensive patterns

Strategy: validation

Validate before calling

$parsed = (new \Symfony\Component\Yaml\Parser())->parseFile($file, Yaml::PARSE_CONSTANT);
if (null !== $parsed && !is_array($parsed)) {
    throw new \InvalidArgumentException("$file must be a YAML mapping of translations");
}

Type guard

if (!is_array($parsed)) { /* reject or coerce */ }

Try / catch

try {
    $translator->addResource('yaml', $file, 'en');
} catch (InvalidResourceException $e) {
    // inspect $e->getMessage(); fix the YAML root node
}

Prevention

Keep translation YAML files as top-level key: value mappings.
Lint translation files in CI with the YAML parser before deployment.
Never register non-translation YAML files as translator resources.

When it happens

Trigger: Loading a translation resource (e.g. via Translatable / Translator->addResource or loadResource) where the YAML file parses successfully with Yaml::PARSE_CONSTANT but yields a non-null, non-array root node such as `foo` or `123` instead of a mapping.

Common situations: A translator edited a messages.yaml file and accidentally replaced the mapping with a single scalar line; an empty-ish file containing just a quoted string; a file that lost its structure after a bad merge; wrong file (e.g. a README or config YAML) registered as a translation resource.

Related errors

AI-assisted analysis of symfony/translation@ae9e8a51bc (2026-09-15). Data as JSON: /api/errors/275596fac95e9b88. Report an issue: GitHub.

Appendix: source

Thrown at Loader/YamlFileLoader.php:46

    protected function loadResource(string $resource): array
    {
        if (!isset($this->yamlParser)) {
            if (!class_exists(YamlParser::class)) {
                throw new LogicException('Loading translations from the YAML format requires the Symfony Yaml component.');
            }

            $this->yamlParser = new YamlParser();
        }

        try {
            $messages = $this->yamlParser->parseFile($resource, Yaml::PARSE_CONSTANT);
        } catch (ParseException $e) {
            throw new InvalidResourceException(\sprintf('The file "%s" does not contain valid YAML: ', $resource).$e->getMessage(), 0, $e);
        }

        if (null !== $messages && !\is_array($messages)) {
            throw new InvalidResourceException(\sprintf('Unable to load file "%s".', $resource));
        }

        return $messages ?: [];
    }
}

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