twigphp/Twig · error · Twig\Error\RuntimeError

Unknown attribute type

Error message

Unknown attribute type "%s" The only supported types are "sst", "cst" and "style".

What it means

The html_attr() helper supports special attribute-value types via the htmlAttrType() converter: 'sst' (space-separated token list), 'cst' (comma-separated token list) and 'style' (inline CSS). Any other type string hits the match() default arm and throws this RuntimeError.

Solutions

1. Use only 'sst', 'cst' or 'style' as the type argument.
2. Fix typos ('styles' -> 'style', 'csv' -> 'cst').
3. Validate/config-whitelist the type value before passing it through.
4. If you need a new type, extend with your own AttributeValueInterface implementation instead of a new string.

Example fix

// before
htmlAttrType($value, 'csv')
// after
htmlAttrType($value, 'cst')

if (!in_array($type, ['sst','cst','style'], true)) { throw new \InvalidArgumentException("Unsupported attr type $type"); }

function isSupportedAttrType(string $t): bool { return in_array($t, ['sst','cst','style'], true); }

try { $v = HtmlExtension::htmlAttrType($value, $type); } catch (Twig\Error\RuntimeError $e) { $v = new SeparatedTokenList($value, ' '); }

When it happens

Trigger: Calling HtmlExtension::htmlAttrType($value, $type) with $type not in ['sst','cst','style'], e.g. htmlAttrType($value, 'class') or a typo like 'styles'.

Common situations: Typo in the type string in a Twig template; copying an option name from another helper; passing user-controlled type config that was never validated.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Only empty strings may be passed as string arguments to…
• Cannot merge incompatible values for key
• The " " attribute value cannot be JSON encoded.
• The " " attribute value should be a scalar, an iterable, or…
• Enum " " does not exist.

AI-assisted analysis of twigphp/Twig@a414c3a491 (2026-09-13). Data as JSON: /api/errors/76b9c52f5d644c65. Report an issue: GitHub.

Appendix: source

Thrown at extra/html-extra/HtmlExtension.php:145

     * @param array<string, array<string, string|array<string>>> $variants
     * @param array<array<string, string|array<string>>>         $compoundVariants
     * @param array<string, string>                              $defaultVariant
     *
     * @internal
     */
    public static function htmlCva(array|string $base = [], array $variants = [], array $compoundVariants = [], array $defaultVariant = []): Cva
    {
        return new Cva($base, $variants, $compoundVariants, $defaultVariant);
    }

    /** @internal */
    public static function htmlAttrType(mixed $value, string $type = 'sst'): AttributeValueInterface
    {
        return match ($type) {
            'sst' => new SeparatedTokenList($value, ' '),
            'cst' => new SeparatedTokenList($value, ', '),
            'style' => new InlineStyle($value),
            default => throw new RuntimeError(\sprintf('Unknown attribute type "%s" The only supported types are "sst", "cst" and "style".', $type)),
        };
    }

    /** @internal */
    public static function htmlAttrMerge(iterable|string|false|null ...$arrays): array
    {
        $result = [];

        foreach ($arrays as $array) {
            if (!$array) {
                continue;
            }

            if (\is_string($array)) {
                throw new RuntimeError('Only empty strings may be passed as string arguments to html_attr_merge. This is to support the implicit else clause for ternary operators.');
            }

            foreach ($array as $key => $value) {

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