[BugFix] Graph Ql category tree structure is lost (children all grouped with last item)

[raivisdejus]

Preconditions

Magento 2.3-develop

Steps to reproduce

Run the following Graph Ql query

{
    category(id: 2) {
        children {
            name
            children {
                name
                children {
                    name
                    children {
                        name
                    }
                }
            }
        }
    }
}

Expected result

Category tree with categories and their children. Tree matches site category structure

Actual result

Categories are sorted according to their levels where last items get all the children.

[raivisdejus]

Fix with tests for this issue has been prepared and will be uploaded for code review and pull request soon.

[danslo]

Ran into this as well. We're currently using the following diff to work around it for now:

diff --git a/Model/Resolver/Products/DataProvider/CategoryTree.php b/Model/Resolver/Products/DataProvider/CategoryTree.php
index bae9def4ee6..8201c6d7819 100644
--- a/Model/Resolver/Products/DataProvider/CategoryTree.php
+++ b/Model/Resolver/Products/DataProvider/CategoryTree.php
@@ -98,29 +98,33 @@ class CategoryTree
         $collection->addPathFilter(sprintf('.*/%s/[/0-9]*$', $rootCategoryId));
         $collection->addFieldToFilter('level', ['gt' => $level]);
         $collection->addFieldToFilter('level', ['lteq' => $level + $depth - self::DEPTH_OFFSET]);
-        $collection->setOrder('level');
+        $collection->setOrder('path');
         $collection->getSelect()->orWhere(
             $this->metadata->getMetadata(CategoryInterface::class)->getIdentifierField() . ' = ?',
             $rootCategoryId
         );
-        return $this->processTree($collection->getIterator());
+        return $this->processTree($collection->getIterator(), $level);
     }
 
     /**
      * @param \Iterator $iterator
      * @return array
      */
-    private function processTree(\Iterator $iterator) : array
+    private function processTree(\Iterator $iterator, $currentLevel) : array
     {
         $tree = [];
         while ($iterator->valid()) {
             /** @var CategoryInterface $category */
             $category = $iterator->current();
+            if ($currentLevel > $category->getLevel()) {
+                break;
+            }
             $iterator->next();
             $nextCategory = $iterator->current();
             $tree[$category->getId()] = $this->hydrator->hydrateCategory($category);
-            if ($nextCategory && (int) $nextCategory->getLevel() !== (int) $category->getLevel()) {
-                $tree[$category->getId()]['children'] = $this->processTree($iterator);
+            if ($nextCategory && $nextCategory->getLevel() > $category->getLevel()) {
+                $tree[$nextCategory->getParentId()]['children'] =
+                    $this->processTree($iterator, $nextCategory->getLevel());
             }
         }

Probably not the most elegant way, and also 2.3-develop has refactored many parts and this diff applies on 2.3.0 only.

Looking forward to a "proper" patch :)

[nuzil]

It was fixed within this PR and merged
#164

[raivisdejus]

Glad to hear this was fixed

[naydav]

#343