imp(src/args): Exposes argument display order by introducing a new Trait

This commit introduces a new trait (`DispOrder`) with a single function
(`fn disp_order(&self) -> usize`). It is use to expose the display order
of an argument in a read-only manner.

Author: hgrecco

src/args/any_arg.rs

@@ -26,3 +26,7 @@ pub trait AnyArg<'n, 'e> {
     fn help(&self) -> Option<&'e str>;
     fn default_val(&self) -> Option<&'n str>;
 }
+
+pub trait DispOrder {
+    fn disp_ord(&self) -> usize;
+}

src/args/arg_builder/flag.rs

@@ -8,7 +8,7 @@ use std::result::Result as StdResult;
 use vec_map::VecMap;
 
 use Arg;
-use args::{AnyArg, HelpWriter};
+use args::{AnyArg, HelpWriter, DispOrder};
 use args::settings::{ArgFlags, ArgSettings};
 
 #[derive(Debug)]
@@ -131,6 +131,10 @@ impl<'n, 'e> AnyArg<'n, 'e> for FlagBuilder<'n, 'e> {
     fn default_val(&self) -> Option<&'n str> { None }
 }
 
+impl<'n, 'e> DispOrder for FlagBuilder<'n, 'e> {
+    fn disp_ord(&self) -> usize { self.disp_ord }
+}
+
 #[cfg(test)]
 mod test {
     use super::FlagBuilder;

src/args/arg_builder/option.rs

@@ -5,7 +5,7 @@ use std::io;
 
 use vec_map::VecMap;
 
-use args::{AnyArg, Arg, HelpWriter};
+use args::{AnyArg, Arg, HelpWriter, DispOrder};
 use args::settings::{ArgFlags, ArgSettings};
 
 #[allow(missing_debug_implementations)]
@@ -195,6 +195,10 @@ impl<'n, 'e> AnyArg<'n, 'e> for OptBuilder<'n, 'e> {
     fn default_val(&self) -> Option<&'n str> { self.default_val }
 }
 
+impl<'n, 'e> DispOrder for OptBuilder<'n, 'e> {
+    fn disp_ord(&self) -> usize { self.disp_ord }
+}
+
 #[cfg(test)]
 mod test {
     use super::OptBuilder;

src/args/arg_builder/positional.rs

@@ -6,7 +6,7 @@ use std::io;
 use vec_map::VecMap;
 
 use Arg;
-use args::{AnyArg, HelpWriter};
+use args::{AnyArg, HelpWriter, DispOrder};
 use args::settings::{ArgFlags, ArgSettings};
 
 #[allow(missing_debug_implementations)]
@@ -182,6 +182,10 @@ impl<'n, 'e> AnyArg<'n, 'e> for PosBuilder<'n, 'e> {
     fn default_val(&self) -> Option<&'n str> { self.default_val }
 }
 
+impl<'n, 'e> DispOrder for PosBuilder<'n, 'e> {
+    fn disp_ord(&self) -> usize { self.disp_ord }
+}
+
 #[cfg(test)]
 mod test {
     use super::PosBuilder;

src/args/mod.rs

@@ -5,7 +5,7 @@ pub use self::subcommand::SubCommand;
 pub use self::arg_builder::{FlagBuilder, OptBuilder, PosBuilder};
 pub use self::matched_arg::MatchedArg;
 pub use self::group::ArgGroup;
-pub use self::any_arg::AnyArg;
+pub use self::any_arg::{AnyArg, DispOrder};
 pub use self::settings::ArgSettings;
 pub use self::help_writer::HelpWriter;