Fix root node siblings not reordered after prepend_child/add_sibling moves root to child position

lib/closure_tree/numeric_deterministic_ordering.rb

@@ -30,6 +30,15 @@ def _ct_reorder_children(minimum_sort_order_value = nil)
       _ct.reorder_with_parent_id(_ct_id, minimum_sort_order_value, scope_conditions)
     end
 
+    def _ct_reorder_prior_parent_or_roots(prior_parent, was_root)
+      if prior_parent
+        prior_parent._ct_reorder_children
+      elsif was_root && !_ct.dont_order_roots
+        scope_conditions = _ct.scope_values_from_instance(self)
+        _ct.reorder_with_parent_id(nil, nil, scope_conditions)
+      end
+    end
+
     def self_and_descendants_preordered
       # TODO: raise NotImplementedError if sort_order is not numeric and not null?
       hierarchy_table = self.class.hierarchy_class.arel_table
@@ -130,11 +139,14 @@ def append_child(child_node)
     end
 
     def prepend_child(child_node)
+      prior_parent = child_node.parent
+      was_root = prior_parent.nil? && child_node.persisted?
       child_node.order_value = -1
       child_node.parent = self
       child_node._ct_skip_sort_order_maintenance!
       if child_node.save
         _ct_reorder_children
+        _ct_reorder_prior_parent_or_roots(prior_parent, was_root)
         child_node.reload
       else
         child_node
@@ -161,6 +173,7 @@ def add_sibling(sibling, add_after = true)
 
       _ct.with_advisory_lock do
         prior_sibling_parent = sibling.parent
+        sibling_was_root = prior_sibling_parent.nil? && sibling.persisted?
         reorder_from_value = if prior_sibling_parent == parent
                                [order_value, sibling.order_value].compact.min
                              else
@@ -184,7 +197,7 @@ def add_sibling(sibling, add_after = true)
           sibling.update_order_value(self_ov)
         end
 
-        prior_sibling_parent.try(:_ct_reorder_children) if prior_sibling_parent != parent
+        sibling._ct_reorder_prior_parent_or_roots(prior_sibling_parent, sibling_was_root) if prior_sibling_parent != parent
         sibling
       end
     end

test/closure_tree/label_order_value_test.rb

@@ -53,4 +53,69 @@ def setup
     assert_equal 1, b.order_value
     assert_equal 2, c.order_value
   end
+
+  test 'should reorder remaining root nodes when a root node becomes a child via prepend_child' do
+    node_1 = Label.create(name: 'node_1')
+    node_2 = Label.create(name: 'node_2')
+    node_3 = Label.create(name: 'node_3')
+    node_4 = Label.create(name: 'node_4')
+
+    # Verify initial positions
+    assert_equal 0, node_1.order_value
+    assert_equal 1, node_2.order_value
+    assert_equal 2, node_3.order_value
+    assert_equal 3, node_4.order_value
+
+    # Move node_2 as a child of node_3 using prepend_child
+    node_3.prepend_child(node_2)
+
+    # Reload all nodes to get updated positions
+    node_1.reload
+    node_2.reload
+    node_3.reload
+    node_4.reload
+
+    # Verify node_2 is now a child of node_3 with position 0
+    assert_equal node_3.id, node_2._ct_parent_id
+    assert_equal 0, node_2.order_value
+
+    # Verify remaining root nodes have sequential positions without gaps
+    assert_equal 0, node_1.order_value
+    assert_equal 1, node_3.order_value
+    assert_equal 2, node_4.order_value
+  end
+
+  test 'should reorder remaining root nodes when a root node becomes a child via add_sibling' do
+    node_1 = Label.create(name: 'node_1')
+    node_2 = Label.create(name: 'node_2')
+    node_3 = Label.create(name: 'node_3')
+    node_4 = Label.create(name: 'node_4')
+
+    # Create a child under node_3
+    child = Label.create(name: 'child', parent: node_3)
+
+    # Verify initial positions
+    assert_equal 0, node_1.order_value
+    assert_equal 1, node_2.order_value
+    assert_equal 2, node_3.order_value
+    assert_equal 3, node_4.order_value
+    assert_equal 0, child.order_value
+
+    # Move node_2 as a sibling of child (making it a child of node_3)
+    child.add_sibling(node_2)
+
+    # Reload all nodes to get updated positions
+    node_1.reload
+    node_2.reload
+    node_3.reload
+    node_4.reload
+
+    # Verify node_2 is now a child of node_3
+    assert_equal node_3.id, node_2._ct_parent_id
+
+    # Verify remaining root nodes have sequential positions without gaps
+    assert_equal 0, node_1.order_value
+    assert_equal 1, node_3.order_value
+    assert_equal 2, node_4.order_value
+  end
 end