Set default tree group for core trees (#11801)

Co-authored-by: Elitsa Marinovska <[email protected]>

Author: bjarnef

src/Umbraco.Core/Extensions/TypeExtensions.cs

@@ -430,10 +430,16 @@ public static IEnumerable<T> GetCustomAttributes<T>(this Type type, bool inherit
             where T : Attribute
         {
             if (type == null) return Enumerable.Empty<T>();
-            return type.GetCustomAttributes(typeof (T), inherited).OfType<T>();
+            return type.GetCustomAttributes(typeof(T), inherited).OfType<T>();
         }
 
-          /// <summary>
+        public static bool HasCustomAttribute<T>(this Type type, bool inherit)
+            where T : Attribute
+        {
+            return type.GetCustomAttribute<T>(inherit) != null;
+        }
+
+        /// <summary>
         /// Tries to return a value based on a property name for an object but ignores case sensitivity
         /// </summary>
         /// <param name="type"></param>

src/Umbraco.Web.BackOffice/Trees/TreeCollectionBuilder.cs

@@ -48,6 +48,12 @@ public void AddTreeController(Type controllerType)
 
             var attribute = controllerType.GetCustomAttribute<TreeAttribute>(false);
             if (attribute == null) return;
+
+            bool isCoreTree = controllerType.HasCustomAttribute<CoreTreeAttribute>(false);
+
+            // Use section as tree group if core tree, so it isn't grouped by empty key and thus end up in "Third Party" tree group if adding custom tree nodes in other groups, e.g. "Settings" tree group.
+            attribute.TreeGroup = attribute.TreeGroup ?? (isCoreTree ? attribute.SectionAlias : attribute.TreeGroup);
+
             var tree = new Tree(attribute.SortOrder, attribute.SectionAlias, attribute.TreeGroup, attribute.TreeAlias, attribute.TreeTitle, attribute.TreeUse, controllerType, attribute.IsSingleNodeTree);
             _trees.Add(tree);
         }