fix: move block

collab-document/src/document.rs

@@ -296,10 +296,12 @@ impl Document {
  let new_parent_children_id = new_parent.children;
  let old_parent_children_id = old_parent.children;
 
- // If the new parent is the same as the old parent, just return.
- if new_parent_children_id == old_parent_children_id {
- return Ok(());
- }
+ // It must delete the block from the old parent.
+ // And this operation must be done before insert the block to the new parent,
+ // because the block may be moved to the same parent.
+ self
+ .children_operation
+ .delete_child_with_txn(txn, &old_parent_children_id, block_id);
 
  // If the prev_id is not found, insert the block to the first position.
  // so the default index is 0.
@@ -312,11 +314,6 @@ impl Document {
  .map(|prev_index| prev_index + 1)
  .unwrap_or(0);
 
- // Delete the block from the old parent.
- self
- .children_operation
- .delete_child_with_txn(txn, &old_parent_children_id, block_id);
-
  // Insert the block to the new parent.
  self
  .children_operation