Fix category tree in cart price rule #17493

Author: Krzysztof Wolowski

app/code/Magento/Catalog/view/adminhtml/web/js/category-checkbox-tree.js

@@ -230,6 +230,7 @@ define([
 
             categoryLoader.on('beforeload', function (treeLoader, node) {
                 treeLoader.baseParams.id = node.attributes.id;
+                treeLoader.baseParams.selected = options.jsFormObject.updateElement.value;
             });
 
             /* eslint-disable */

app/code/Magento/CatalogRule/Controller/Adminhtml/Promo/Widget/CategoriesJson.php

@@ -77,10 +77,11 @@ public function execute()
             if (!($category = $this->_initCategory())) {
                 return;
             }
+            $selected = $this->getRequest()->getPost('selected', '');
             $block = $this->_view->getLayout()->createBlock(
                 \Magento\Catalog\Block\Adminhtml\Category\Checkboxes\Tree::class
             )->setCategoryIds(
-                [$categoryId]
+                explode(',', $selected)
             );
             $this->getResponse()->representJson(
                 $block->getTreeJson($category)