Function render 

pub fn render(url: &Url, absolute_path: bool) -> String

The single place the synthetic root is stripped. A URL that is not under it is its own text. A synthetic URL with an authority (//host/x) keeps its //host/x form. Otherwise the path is returned as a reference: relative (the leading / of the synthetic root removed, so nothing can climb out of it) unless absolute_path says the MPD wrote an absolute-path reference.