Is there a way to prevent the space in autocomplete?

I want to have a multi-step autocomplete (think autocompleting a deep js property).

```
parent
child
prop
```

I want to be able to type `par` and autocomplete to `parent.` (without a space) and on next tab, my custom autocomplete will offer "child" and autocomplete to `parent.child.`. I've looked at the code and it seems like the space is added in all cases but a slash. I think it would be useful for the custom autocomplete function to be able to control that somehow.

Thanks