How to copy ListItems from one Google Document to another while preserving numbering? - google-apps-script

Question

The accepted answer to How to copy content and formatting between Google Docs? indicates that we have to add conditional code just to copy elements. But I cannot get it to work for ListItem types, because the target document shows the list items without the original numbering.
var source_doc = DocumentApp.getActiveDocument();
var selection = source_doc.getSelection();
if (!selection) {
var ui = DocumentApp.getUi();
ui.alert('Please make a selection first.');
return;
}
var target_doc = DocumentApp.create('CopyOf'+DocumentApp.getActiveDocument().getName());
var target_body = target_doc.getBody();
var elements = selection.getRangeElements();
for (var i = 1; i < elements.length; i++) {
var source_element = elements[i].getElement();
var copy_element = source_element.copy();
if (copy_element.getType() == DocumentApp.ElementType.PARAGRAPH) {
target_body.appendParagraph(copy_element);
} else if (copy_element.getType() == DocumentApp.ElementType.LIST_ITEM) {
// This does not keep the numbering on the list item. Why?
target_body.appendListItem(copy_element);
// And playing games with setListId doesn't work either:
// copy_element.setListId(source_element);
// target_body.appendListItem(copy_element);
}
// TODO: Handle the other elements here.
}
The source document displays like this:
Target document renders like this:
How do I preserve ListItem formatting?
This seems much much harder than it should be: What I really want is to copy the users selection verbatim into a new document preserving all formatting, and from a google script.
It would seem that this could be done at a higher level. I can manually copy and paste and preserve the formatting, just not from the script.

Answer 1

I'm guessing that the cause of this is that there's a problem with using a Selection. Reading from a document directly seems to work fine.
Try appending the ListItem as text as a workaround.
target_body.appendListItem(copy_element.getText());
This will only copy the text though, not the formatting. You can also try to implement it by making a new list instead of copying the element directly. Here's a sample SO that might help.

Answer 2

I was having a similar problem (but not using a selection). It was being copied as a list but without any actual bullets. I just re-set the bullets manually like this:
target_body.appendListItem(copy_element).setGlyphType(DocumentApp.GlyphType.NUMBER)