default_value from lazy Default #150
Description
(Hello, I'm still not sure if this should be on structopt or clap-rs..),
This is a feature request so default_value may be used without any value (like short/long), and be lazily derived from Default itself.
Quick example:
from this:
#[derive(Clone, Debug, StructOpt)]
pub struct Config {
#[structopt(raw(default_value = "&DEFAULT_CONFIG_BIND_ADDR_STR"))]
pub bind_addr: SocketAddr,
}
impl Default for Config {
fn default() -> Self {
Self {
bind_addr: FromStr::from_str("127.0.0.1:8080").unwrap()
}
}
}
// interface between `Default::default()` and (structopt) `default_value`
lazy_static! {
static ref DEFAULT_CONFIG: Config = Config::default();
static ref DEFAULT_CONFIG_BIND_ADDR_STR: String = DEFAULT_CONFIG.bind_addr.to_string();
// (for fields that has no to_string(), I'm "manually" implementing (interfacing) it with some serde serialization by implementing Display)
}
// lazy_static is needed so &'static str may be used. I don't know how different parsing choices would be dealt with..into this:
#[derive(Clone, Debug, StructOpt)]
#[structopt(default_value)]
pub struct Config {
pub bind_addr: SocketAddr,
}
impl Default for Config {
fn default() -> Self {
Self {
bind_addr: FromStr::from_str("127.0.0.1:8080").unwrap()
}
}
}Sorry in advance if this is actually a bad design choice (then I should have no intention of asking for such feature), and that I can't really point into any macro derivation specifics. It's magic !!