Migrate discussions when transitioning article to i18n

wcfsetup/install/files/lib/command/article/EnableI18n.class.php

@@ -4,9 +4,14 @@
 
 use wcf\data\article\Article;
 use wcf\data\article\ArticleAction;
+use wcf\data\article\content\ArticleContent;
 use wcf\data\article\content\ArticleContentAction;
+use wcf\data\article\content\ArticleContentEditor;
+use wcf\data\object\type\ObjectTypeCache;
+use wcf\system\article\discussion\IArticleDiscussionProvider;
 use wcf\system\language\LanguageFactory;
 use wcf\system\version\VersionTracker;
+use wcf\system\WCF;
 
 /**
  * Converts a monolingual article to a multilingual.
@@ -36,14 +41,19 @@ public function __invoke(): void
             ];
         }
 
+        $discussionProvider = $this->article->getDiscussionProvider();
+
         $action = new ArticleAction([$this->article], 'update', [
             'content' => $data,
             'data' => [
                 'isMultilingual' => 1,
             ],
+            'migrateDiscussions' => true,
         ]);
         $action->executeAction();
 
+        $this->migrateDiscussions($discussionProvider, $this->article, $articleContent);
+
         $action = new ArticleContentAction([$articleContent], 'delete');
         $action->executeAction();
 
@@ -52,4 +62,22 @@ public function __invoke(): void
             $this->article->articleID
         );
     }
+
+    /**
+     * Preserves the comments by associating the existing comments with the
+     * content matching the site’s default language id.
+     */
+    private function migrateDiscussions(IArticleDiscussionProvider $discussionProvider, Article $article, ArticleContent $oldContent): void
+    {
+        $article = new Article($article->articleID);
+        $newContent = $article->getArticleContents()[LanguageFactory::getInstance()->getDefaultLanguageID()] ?? null;
+        if ($newContent === null) {
+            // This shouldn’t be possible but throwing an exception here would
+            // yield a malformed article that cannot be fixed except through
+            // manual editing of the database.
+            return;
+        }
+
+        $discussionProvider->migrateDiscussions($oldContent, $newContent);
+    }
 }

wcfsetup/install/files/lib/system/article/discussion/AbstractArticleDiscussionProvider.class.php

@@ -26,21 +26,17 @@ abstract class AbstractArticleDiscussionProvider implements IArticleDiscussionPr
      */
     protected $articleContent;
 
-    /**
-     * AbstractArticleDiscussionProvider constructor.
-     *
-     * @param Article $article
-     */
     public function __construct(Article $article)
     {
         $this->article = $article;
     }
 
-    /**
-     * @inheritDoc
-     */
+    #[\Override]
     public function setArticleContent(ArticleContent $articleContent)
     {
         $this->articleContent = $articleContent;
     }
+
+    #[\Override]
+    public function migrateDiscussions(ArticleContent $oldContent, ArticleContent $newContent): void {}
 }

wcfsetup/install/files/lib/system/article/discussion/CommentArticleDiscussionProvider.class.php

@@ -3,6 +3,9 @@
 namespace wcf\system\article\discussion;
 
 use wcf\data\article\Article;
+use wcf\data\article\content\ArticleContent;
+use wcf\data\article\content\ArticleContentEditor;
+use wcf\data\object\type\ObjectTypeCache;
 use wcf\system\comment\CommentHandler;
 use wcf\system\WCF;
 
@@ -12,21 +15,16 @@
  * @author      Alexander Ebert
  * @copyright   2001-2019 WoltLab GmbH
  * @license     GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @since       5.2
  */
 class CommentArticleDiscussionProvider extends AbstractArticleDiscussionProvider
 {
-    /**
-     * @inheritDoc
-     */
+    #[\Override]
     public function getDiscussionCount()
     {
         return $this->articleContent ? $this->articleContent->comments : $this->article->getArticleContent()->comments;
     }
 
-    /**
-     * @inheritDoc
-     */
+    #[\Override]
     public function getDiscussionCountPhrase()
     {
         return WCF::getLanguage()->getDynamicVariable('wcf.article.articleComments', [
@@ -35,17 +33,13 @@ public function getDiscussionCountPhrase()
         ]);
     }
 
-    /**
-     * @inheritDoc
-     */
+    #[\Override]
     public function getDiscussionLink()
     {
         return $this->articleContent->getLink() . '#comments';
     }
 
-    /**
-     * @inheritDoc
-     */
+    #[\Override]
     public function renderDiscussions()
     {
         $commentCanAdd = WCF::getSession()->getPermission('user.article.canAddComment');
@@ -66,6 +60,31 @@ public function renderDiscussions()
         ]);
     }
 
+    #[\Override]
+    public function migrateDiscussions(ArticleContent $oldContent, ArticleContent $newContent): void
+    {
+        $objectTypeID = ObjectTypeCache::getInstance()->getObjectTypeIDByName(
+            'com.woltlab.wcf.comment.commentableContent',
+            'com.woltlab.wcf.articleComment',
+        );
+        \assert($objectTypeID !== null);
+
+        $sql = "UPDATE  wcf1_comment
+                SET     objectID = ?
+                WHERE   objectTypeID = ?
+                    AND objectID = ?";
+        $statement = WCF::getDB()->prepare($sql);
+        $statement->execute([
+            $newContent->articleContentID,
+            $objectTypeID,
+            $oldContent->articleContentID,
+        ]);
+
+        (new ArticleContentEditor($newContent))->update([
+            'comments' => $oldContent->comments,
+        ]);
+    }
+
     /**
      * @inheritDoc
      */

wcfsetup/install/files/lib/system/article/discussion/IArticleDiscussionProvider.class.php

@@ -58,4 +58,12 @@ public function setArticleContent(ArticleContent $articleContent);
      * @return bool
      */
     public static function isResponsible(Article $article);
+
+    /**
+     * Migrates discussions from one content to another. This is intended to be
+     * used when converting a monolingual article into a multilingual one.
+     *
+     * @since 6.2
+     */
+    public function migrateDiscussions(ArticleContent $oldContent, ArticleContent $newContent): void;
 }