Add a helpful error message when there are no article categories

See https://www.woltlab.com/community/thread/313610/

Author: dtdesign

wcfsetup/install/files/lib/acp/form/ArticleAddForm.class.php

@@ -16,6 +16,7 @@
 use wcf\system\attachment\AttachmentHandler;
 use wcf\system\bbcode\BBCodeHandler;
 use wcf\system\cache\builder\ArticleCategoryLabelCacheBuilder;
+use wcf\system\exception\NamedUserException;
 use wcf\system\exception\UserInputException;
 use wcf\system\html\input\HtmlInputProcessor;
 use wcf\system\html\upcast\HtmlUpcastProcessor;
@@ -26,6 +27,7 @@
 use wcf\util\ArrayUtil;
 use wcf\util\DateUtil;
 use wcf\util\HeaderUtil;
+use wcf\util\HtmlString;
 use wcf\util\StringUtil;
 
 /**
@@ -226,13 +228,23 @@ class ArticleAddForm extends AbstractForm
      */
     public $attachmentObjectType = 'com.woltlab.wcf.article';
 
+    protected CategoryNodeTree $categoryNodeTree;
+
     /**
      * @inheritDoc
      */
     public function readParameters()
     {
         parent::readParameters();
 
+
+        $this->categoryNodeTree = new CategoryNodeTree('com.woltlab.wcf.article.category');
+        if (\iterator_count($this->categoryNodeTree->getIterator()) === 0) {
+            throw new NamedUserException(
+                HtmlString::fromSafeHtml(WCF::getLanguage()->getDynamicVariable('wcf.acp.article.category.error.noCategories'))
+            );
+        }
+
         if (isset($_REQUEST['categoryID'])) {
             $this->categoryID = \intval($_REQUEST['categoryID']);
         }
@@ -707,7 +719,7 @@ public function assignVariables()
             'teaser' => $this->teaser,
             'content' => $this->content,
             'availableLanguages' => $this->availableLanguages,
-            'categoryNodeList' => (new CategoryNodeTree('com.woltlab.wcf.article.category'))->getIterator(),
+            'categoryNodeList' => $this->categoryNodeTree->getIterator(),
             'accessibleCategoryIDs' => ArticleCategory::getAccessibleCategoryIDs(),
             'labelIDs' => $this->labelIDs,
             'labelGroups' => $this->labelGroups,

wcfsetup/install/lang/de.xml

@@ -84,6 +84,7 @@
 		<item name="wcf.acp.article.category.sortField"><![CDATA[Sortierung]]></item>
 		<item name="wcf.acp.article.category.sortField.publicationDate"><![CDATA[Veröffentlichungsdatum]]></item>
 		<item name="wcf.acp.article.category.sortField.title"><![CDATA[Titel]]></item>
+		<item name="wcf.acp.article.category.error.noCategories"><![CDATA[Bevor {if LANGUAGE_USE_INFORMAL_VARIANT}du{else}Sie{/if} einen Artikel erstellen {if LANGUAGE_USE_INFORMAL_VARIANT}kannst, musst du{else}könne, müssen Sie{/if} eine <a href="{link controller='ArticleCategoryAdd' isACP=true}{/link}">Kategorie anlegen</a>.]]></item>
 		<item name="wcf.acp.article.content"><![CDATA[Inhalt]]></item>
 		<item name="wcf.acp.article.enableComments"><![CDATA[Kommentare aktivieren]]></item>
 		<item name="wcf.acp.article.i18n"><![CDATA[Mehrsprachigkeit]]></item>

wcfsetup/install/lang/en.xml

@@ -84,6 +84,7 @@
 		<item name="wcf.acp.article.category.sortField"><![CDATA[Show Order]]></item>
 		<item name="wcf.acp.article.category.sortField.publicationDate"><![CDATA[Publication Date]]></item>
 		<item name="wcf.acp.article.category.sortField.title"><![CDATA[Title]]></item>
+		<item name="wcf.acp.article.category.error.noCategories"><![CDATA[Please <a href="{link controller='ArticleCategoryAdd' isACP=true}{/link}">add a category</a> before writing articles.]]></item>
 		<item name="wcf.acp.article.content"><![CDATA[Content]]></item>
 		<item name="wcf.acp.article.enableComments"><![CDATA[Enable comments]]></item>
 		<item name="wcf.acp.article.i18n"><![CDATA[Multilingualism]]></item>