core-bundle/src/Routing/UrlGenerator.php
private function prepareAlias(string $alias, array &$parameters): void
    {
        if ('index' === $alias) {
            return;
        }

        $hasAutoItem = false;
        $autoItems = $this->getAutoItems($parameters);

        /** @var Config $config */
        $config = $this->framework->getAdapter(Config::class);

        $parameters['alias'] = preg_replace_callback(
            '/\{([^\}]+)\}/',
            static function (array $matches) use ($alias, &$parameters, $autoItems, &$hasAutoItem, $config): string {
                $param = $matches[1];

                if (!isset($parameters[$param])) {
                    throw new MissingMandatoryParametersException(
                        sprintf('Parameters "%s" is missing to generate a URL for "%s"', $param, $alias)
                    );
                }

                $value = $parameters[$param];
                unset($parameters[$param]);

                if ($hasAutoItem || !$config->get('useAutoItem') || !\in_array($param, $autoItems, true)) {
                    return $param.'/'.$value;
                }

                $hasAutoItem = true;

                return $value;
            },
            $alias
        );
    }
private function prepareAlias(string $alias, array &$parameters): void
    {
        if ('index' === $alias) {
            return;
        }

        $hasAutoItem = false;
        $autoItems = $this->getAutoItems($parameters);

        /** @var Config $config */
        $config = $this->framework->getAdapter(Config::class);

        $parameters['alias'] = preg_replace_callback(
            '/\{([^\}]+)\}/',
            static function (array $matches) use ($alias, &$parameters, $autoItems, &$hasAutoItem, $config): string {
                $param = $matches[1];

                if (!isset($parameters[$param])) {
                    throw new MissingMandatoryParametersException(
                        sprintf('Parameters "%s" is missing to generate a URL for "%s"', $param, $alias)
                    );
                }

                $value = $parameters[$param];
                unset($parameters[$param]);

                if ($hasAutoItem || !$config->get('useAutoItem') || !\in_array($param, $autoItems, true)) {
                    return $param.'/'.$value;
                }

                $hasAutoItem = true;

                return $value;
            },
            $alias
        );
    }
Adds the parameters to the alias.

@throws MissingMandatoryParametersException