Function dev_formatter 

pub fn dev_formatter(
    conn: &Conn,
    color: bool,
) -> impl Display + Send + 'static + use<>

Available on crate feature client only.

The default development-mode formatter.

Composed of:

"version method url() status response_time"

The error() component is empty on success. When the transport failed, it renders as <error message> — the leading space is part of the formatter, so the format string is concatenation, not separator-joined.