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    <h3>Editing: HostTrait.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Routing\Loader\Configurator\Traits;

use Symfony\Component\Routing\RouteCollection;

/**
 * @internal
 */
trait HostTrait
{
    final protected function addHost(RouteCollection $routes, $hosts)
    {
        if (!$hosts || !\is_array($hosts)) {
            $routes-&gt;setHost($hosts ?: '');

            return;
        }

        foreach ($routes-&gt;all() as $name =&gt; $route) {
            if (null === $locale = $route-&gt;getDefault('_locale')) {
                $routes-&gt;remove($name);
                foreach ($hosts as $locale =&gt; $host) {
                    $localizedRoute = clone $route;
                    $localizedRoute-&gt;setDefault('_locale', $locale);
                    $localizedRoute-&gt;setRequirement('_locale', preg_quote($locale));
                    $localizedRoute-&gt;setDefault('_canonical_route', $name);
                    $localizedRoute-&gt;setHost($host);
                    $routes-&gt;add($name.'.'.$locale, $localizedRoute);
                }
            } elseif (!isset($hosts[$locale])) {
                throw new \InvalidArgumentException(sprintf('Route &quot;%s&quot; with locale &quot;%s&quot; is missing a corresponding host in its parent collection.', $name, $locale));
            } else {
                $route-&gt;setHost($hosts[$locale]);
                $route-&gt;setRequirement('_locale', preg_quote($locale));
                $routes-&gt;add($name, $route);
            }
        }
    }
}
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