Allow adding fields to an enum variant in Command!

To be able to use the enums generated by Command! with structopt, we
have to be able to add fields to them.  This patch adds a new variant to
the Command! macro that supports fields.

src/arg_util.rs

@@ -25,6 +25,58 @@ macro_rules! count {
 }
 
 macro_rules! Command {
+ ( $name:ident, [ $( $var:ident($inner:ident) => ($str:expr, $exec:expr), ) *] ) => {
+ #[derive(Debug, PartialEq, structopt::StructOpt)]
+ pub enum $name {
+ $(
+ $var($inner),
+ )*
+ }
+
+ impl ::std::convert::AsRef<str> for $name {
+ fn as_ref(&self) -> &'static str {
+ match *self {
+ $(
+ $name::$var(_) => $str,
+ )*
+ }
+ }
+ }
+
+ impl ::std::fmt::Display for $name {
+ fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+ write!(f, "{}", self.as_ref())
+ }
+ }
+
+ impl ::std::str::FromStr for $name {
+ type Err = &'static str;
+
+ fn from_str(s: &str) -> ::std::result::Result<Self, Self::Err> {
+ match s {
+ $(
+ $str => Ok($name::$var(::std::default::Default::default())),
+ )*
+ _ => Err("[error]"),
+ }
+ }
+ }
+
+ #[allow(unused_qualifications)]
+ impl $name {
+ fn execute(
+ self,
+ ctx: &mut crate::args::ExecCtx<'_>,
+ args: ::std::vec::Vec<::std::string::String>,
+ ) -> crate::Result<()> {
+ match self {
+ $(
+ $name::$var(_) => $exec(ctx, args),
+ )*
+ }
+ }
+ }
+ };
  ( $name:ident, [ $( $var:ident => ($str:expr, $exec:expr), ) *] ) => {
  #[derive(Debug, PartialEq)]
  pub enum $name {