Here's an idea: Instead of an HTML string, we produce a Vec<TextOrTag>, which we can optimize more easily, and convert it to HTML in a second step. The enum would be

enum TextOrTag<'s> {
    Text(&'s str),
    OpenTag(Style),
    CloseTag,
    Removed,
}

And the optimization pass could look something like

let mut idx = 0;
while let Some(elem) = list.get(idx) {
    match elem {
        TextOrTag::OpenTag(_) => {
            if let Some(end_idx) = find_end_empty(&list, idx) {
                list[idx] = TextOrTag::Removed;
                list[end_idx] = TextOrTag::Removed;
                idx = end_idx;
            }
        }
        TextOrTag::CloseTag => {
            if let Some(start_idx) = find_start_empty(&list, idx) {
                list[start_idx] = TextOrTag::Removed;
                list[idx] = TextOrTag::Removed;
            }
        }
        _ => {},
    }
    idx += 1;
}

This would even work recursively (e.g. <u><b></b></u>), which we currently don't remove completely.

100% agree! After more of the pending minifier changes shake out I was planning on moving all of the optimizations to operate on the abstract HTML before we emit it since it's way easier to handle optimizations there (as opposed to trying to massage the parsed ansi values)

Gonna go ahead and handle moving the current minifier to work on an abstract HTML representation and then I'll revise this PR and #42