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    <h3>Editing: TargetOperation.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\Translation\Catalogue;

use Symfony\Component\Translation\MessageCatalogueInterface;

/**
 * Target operation between two catalogues:
 * intersection = source ∩ target = {x: x ∈ source ∧ x ∈ target}
 * all = intersection ∪ (target ∖ intersection) = target
 * new = all ∖ source = {x: x ∈ target ∧ x ∉ source}
 * obsolete = source ∖ all = source ∖ target = {x: x ∈ source ∧ x ∉ target}
 * Basically, the result contains messages from the target catalogue.
 *
 * @author Michael Lee &lt;michael.lee@zerustech.com&gt;
 */
class TargetOperation extends AbstractOperation
{
    /**
     * {@inheritdoc}
     */
    protected function processDomain(string $domain)
    {
        $this-&gt;messages[$domain] = [
            'all' =&gt; [],
            'new' =&gt; [],
            'obsolete' =&gt; [],
        ];
        $intlDomain = $domain.MessageCatalogueInterface::INTL_DOMAIN_SUFFIX;

        // For 'all' messages, the code can't be simplified as ``$this-&gt;messages[$domain]['all'] = $target-&gt;all($domain);``,
        // because doing so will drop messages like {x: x ∈ source ∧ x ∉ target.all ∧ x ∈ target.fallback}
        //
        // For 'new' messages, the code can't be simplified as ``array_diff_assoc($this-&gt;target-&gt;all($domain), $this-&gt;source-&gt;all($domain));``
        // because doing so will not exclude messages like {x: x ∈ target ∧ x ∉ source.all ∧ x ∈ source.fallback}
        //
        // For 'obsolete' messages, the code can't be simplified as ``array_diff_assoc($this-&gt;source-&gt;all($domain), $this-&gt;target-&gt;all($domain))``
        // because doing so will not exclude messages like {x: x ∈ source ∧ x ∉ target.all ∧ x ∈ target.fallback}

        foreach ($this-&gt;source-&gt;all($domain) as $id =&gt; $message) {
            if ($this-&gt;target-&gt;has($id, $domain)) {
                $this-&gt;messages[$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);
                }
            } else {
                $this-&gt;messages[$domain]['obsolete'][$id] = $message;
            }
        }

        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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