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    <h3>Editing: MergeOperation.php</h3>
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/*
 * 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\Translation\Catalogue;

use Symfony\Component\Translation\MessageCatalogueInterface;

/**
 * Merge operation between two catalogues as follows:
 * all = source ∪ target = {x: x ∈ source ∨ x ∈ target}
 * new = all ∖ source = {x: x ∈ target ∧ x ∉ source}
 * obsolete = source ∖ all = {x: x ∈ source ∧ x ∉ source ∧ x ∉ target} = ∅
 * Basically, the result contains messages from both catalogues.
 *
 * @author Jean-François Simon &lt;contact@jfsimon.fr&gt;
 */
class MergeOperation extends AbstractOperation
{
    /**
     * {@inheritdoc}
     */
    protected function processDomain(string $domain)
    {
        $this-&gt;messages[$domain] = [
            'all' =&gt; [],
            'new' =&gt; [],
            'obsolete' =&gt; [],
        ];
        $intlDomain = $domain.MessageCatalogueInterface::INTL_DOMAIN_SUFFIX;

        foreach ($this-&gt;source-&gt;all($domain) as $id =&gt; $message) {
            $this-&gt;messages[$domain]['all'][$id] = $message;
            $d = $this-&gt;source-&gt;defines($id, $intlDomain) ? $intlDomain : $domain;
            $this-&gt;result-&gt;add([$id =&gt; $message], $d);
            if (null !== $keyMetadata = $this-&gt;source-&gt;getMetadata($id, $d)) {
                $this-&gt;result-&gt;setMetadata($id, $keyMetadata, $d);
            }
        }

        foreach ($this-&gt;target-&gt;all($domain) as $id =&gt; $message) {
            if (!$this-&gt;source-&gt;has($id, $domain)) {
                $this-&gt;messages[$domain]['all'][$id] = $message;
                $this-&gt;messages[$domain]['new'][$id] = $message;
                $d = $this-&gt;target-&gt;defines($id, $intlDomain) ? $intlDomain : $domain;
                $this-&gt;result-&gt;add([$id =&gt; $message], $d);
                if (null !== $keyMetadata = $this-&gt;target-&gt;getMetadata($id, $d)) {
                    $this-&gt;result-&gt;setMetadata($id, $keyMetadata, $d);
                }
            }
        }
    }
}
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