Moving item to bin doesn't update its siblings sort order

[elit0451]

Which Umbraco version are you using? (Please write the exact version, example: 10.1.0)

13.5.1, 14.3.0, 15 RC

Bug summary

When new document nodes are created, they are always added as the last child. But in the case when you delete an item with sortOrder 0, and add a new one, it will be added as the first item. It seems like this is caused by not recalculating the sortOrder of the siblings when the first item is deleted. This means that the new node comes with sortOrder = 0, which results in taking the position as the first item.

Specifics

No response

Steps to reproduce

• Use a simple content type and create the following tree structure in the Content section:

• Home

  • Child 1
  • Child 2
  • Child 3

• Delete "Child 1"

• Add "Child 4"

---

You can also use the content service and verify that the sortOrder property of each child doesn't reflect the correct value:

var parentId = Home.Id;
IEnumerable<IContent> children = ContentService.GetPagedChildren(parentId, 0, int.MaxValue, out _);

Expected result / actual result

Extected:

• "Child 4" to be added as the last item, so the tree looks like this:

• Home
  • Child 2
  • Child 3
  • Child 4

    
    and the child nodes to have an updated `sortOrder` after deleting "Child 1".

Actual

• "Child 4" is added as the first item, so the tree looks like:

• Home
  • Child 4
  • Child 2
  • Child 3

[elit0451]

The same issue occurs when Moving the first item and adding a new one

[manutdkid77]

Can I pick this one up ? I have been able to figure out why this is happening:

Initially we are removing the first item, which has a sortOrder of 0, and then adding a new item, here it looks like the SortOrderExists method returns false because it cant find any item with sortOrder as 0