feat(arg_aliases): Ability to alias arguments

There are some cases where you need to have an argument to have an
alias, an example could be when you depricate one option in favor of
another one.

Now you are going to be able to alias arguments as follows:
```
Arg::with_name("opt")
    .long("opt")
    .short("o")
    .takes_value(true)
    .alias("invisible")
    .visible_alias("visible")
```

Closes #669

clap-test.rs

@@ -50,6 +50,17 @@ mod test {
         assert_eq!(use_stderr, err.use_stderr());
     }
 
+    pub fn check_subcommand_help(mut a: App, cmd: &str, out: &str) {
+        // We call a get_matches method to cause --help and --version to be built
+        let _ = a.get_matches_from_safe_borrow(vec![""]);
+        let sc = a.p.subcommands.iter().filter(|s| s.p.meta.name == cmd).next().unwrap();
+
+        // Now we check the output of print_help()
+        let mut help = vec![];
+        sc.write_help(&mut help).ok().expect("failed to print help");
+        assert_eq!(str::from_utf8(&help).unwrap(), out);
+    }
+
     pub fn check_help(mut a: App, out: &str) {
         // We call a get_matches method to cause --help and --version to be built
         let _ = a.get_matches_from_safe_borrow(vec![""]);

src/app/parser.rs

@@ -604,7 +604,17 @@ impl<'a, 'b> Parser<'a, 'b>
                     // Check to see if parsing a value from an option
                     if let Some(nvo) = needs_val_of {
                         // get the OptBuilder so we can check the settings
-                        if let Some(opt) = self.opts.iter().find(|o| &o.name == &nvo) {
+                        if let Some(opt) = self.opts
+                            .iter()
+                            .find(|o| {
+                                &o.name == &nvo ||
+                                (o.aliases.is_some() &&
+                                 o.aliases
+                                    .as_ref()
+                                    .unwrap()
+                                    .iter()
+                                    .any(|&(a, _)| a == &*nvo))
+                            }) {
                             needs_val_of = try!(self.add_val_to_arg(opt, &arg_os, matcher));
                             // get the next value from the iterator
                             continue;
@@ -765,7 +775,17 @@ impl<'a, 'b> Parser<'a, 'b>
         if let Some(a) = needs_val_of {
             debugln!("needs_val_of={}", a);
             debug!("Is this an opt...");
-            if let Some(o) = self.opts.iter().find(|o| &o.name == &a) {
+            if let Some(o) = self.opts
+                .iter()
+                .find(|o| {
+                    &o.name == &a ||
+                    (o.aliases.is_some() &&
+                     o.aliases
+                        .as_ref()
+                        .unwrap()
+                        .iter()
+                        .any(|&(n, _)| n == &*a))
+                }) {
                 sdebugln!("Yes");
                 try!(self.validate_required(matcher));
                 reqs_validated = true;
@@ -1213,7 +1233,16 @@ impl<'a, 'b> Parser<'a, 'b>
 
         if let Some(opt) = self.opts
             .iter()
-            .find(|v| v.long.is_some() && &*v.long.unwrap() == arg) {
+            .find(|v|
+                (v.long.is_some() &&
+                 &*v.long.unwrap() == arg) ||
+                (v.aliases.is_some() &&
+                 v.aliases
+                    .as_ref()
+                    .unwrap()
+                    .iter()
+                    .any(|&(n, _)| n == &*arg))
+            ) {
             debugln!("Found valid opt '{}'", opt.to_string());
             let ret = try!(self.parse_opt(val, opt, matcher));
             arg_post_processing!(self, opt, matcher);

src/args/arg.rs

@@ -42,6 +42,8 @@ pub struct Arg<'a, 'b>
     #[doc(hidden)]
     pub long: Option<&'b str>,
     #[doc(hidden)]
+    pub aliases: Option<Vec<(&'b str, bool)>>, // (name, visible)
+    #[doc(hidden)]
     pub help: Option<&'b str>,
     #[doc(hidden)]
     pub index: Option<u64>,
@@ -83,6 +85,7 @@ impl<'a, 'b> Default for Arg<'a, 'b> {
             name: "".as_ref(),
             short: None,
             long: None,
+            aliases: None,
             help: None,
             index: None,
             blacklist: None,
@@ -149,6 +152,7 @@ impl<'a, 'b> Arg<'a, 'b> {
             a = match k.as_str().unwrap() {
                 "short" => yaml_to_str!(a, v, short),
                 "long" => yaml_to_str!(a, v, long),
+                "aliases" => yaml_vec_or_str!(v, a, alias),
                 "help" => yaml_to_str!(a, v, help),
                 "required" => yaml_to_bool!(a, v, required),
                 "takes_value" => yaml_to_bool!(a, v, takes_value),
@@ -409,6 +413,50 @@ impl<'a, 'b> Arg<'a, 'b> {
         self
     }
 
+    /// Add docs
+    pub fn alias<S: Into<&'b str>>(mut self, name: S) -> Self {
+        if let Some(ref mut als) = self.aliases {
+            als.push((name.into(), false));
+        } else {
+            self.aliases = Some(vec![(name.into(), false)]);
+        }
+        self
+    }
+
+    /// Add docs
+    pub fn aliases(mut self, names: &[&'b str]) -> Self {
+        if let Some(ref mut als) = self.aliases {
+            for n in names {
+                als.push((n, false));
+            }
+        } else {
+            self.aliases = Some(names.iter().map(|n| (*n, false)).collect::<Vec<_>>());
+        }
+        self
+    }
+
+    /// Add docs
+    pub fn visible_alias<S: Into<&'b str>>(mut self, name: S) -> Self {
+        if let Some(ref mut als) = self.aliases {
+            als.push((name.into(), true));
+        } else {
+            self.aliases = Some(vec![(name.into(), true)]);
+        }
+        self
+    }
+
+    /// Add docs
+    pub fn visible_aliases(mut self, names: &[&'b str]) -> Self {
+        if let Some(ref mut als) = self.aliases {
+            for n in names {
+                als.push((n, true));
+            }
+        } else {
+            self.aliases = Some(names.iter().map(|n| (*n, true)).collect::<Vec<_>>());
+        }
+        self
+    }
+
     /// Sets the help text of the argument that will be displayed to the user when they print the
     /// usage/help information.
     ///
@@ -2380,6 +2428,7 @@ impl<'a, 'b, 'z> From<&'z Arg<'a, 'b>> for Arg<'a, 'b> {
             name: a.name,
             short: a.short,
             long: a.long,
+            aliases: a.aliases.clone(),
             help: a.help,
             index: a.index,
             possible_vals: a.possible_vals.clone(),
@@ -2407,6 +2456,7 @@ impl<'a, 'b> Clone for Arg<'a, 'b> {
             name: self.name,
             short: self.short,
             long: self.long,
+            aliases: self.aliases.clone(),
             help: self.help,
             index: self.index,
             possible_vals: self.possible_vals.clone(),

src/args/arg_builder/option.rs

@@ -16,6 +16,7 @@ pub struct OptBuilder<'n, 'e> {
     pub name: &'n str,
     pub short: Option<char>,
     pub long: Option<&'e str>,
+    pub aliases: Option<Vec<(&'e str, bool)>>,
     pub help: Option<&'e str>,
     pub blacklist: Option<Vec<&'e str>>,
     pub possible_vals: Option<Vec<&'e str>>,
@@ -39,6 +40,7 @@ impl<'n, 'e> Default for OptBuilder<'n, 'e> {
             name: "",
             short: None,
             long: None,
+            aliases: None,
             help: None,
             blacklist: None,
             possible_vals: None,
@@ -74,6 +76,7 @@ impl<'n, 'e> OptBuilder<'n, 'e> {
             name: a.name,
             short: a.short,
             long: a.long,
+            aliases: a.aliases.clone(),
             help: a.help,
             num_vals: a.num_vals,
             min_vals: a.min_vals,
@@ -157,6 +160,21 @@ impl<'n, 'e> Display for OptBuilder<'n, 'e> {
                         }));
         }
 
+        // Write aliases such as [aliases: alias, new-alias]
+        if let Some(ref vec) = self.aliases {
+            try!(write!(f, " [aliases: "));
+            let mut it = vec.iter().peekable();
+            while let Some(&(val, b)) = it.next() {
+                if b {
+                    try!(write!(f, "{}", val));
+                    if it.peek().is_some() {
+                        try!(write!(f, ", "));
+                    }
+                }
+            }
+            try!(write!(f, "]"));
+        }
+
         Ok(())
     }
 }
@@ -167,6 +185,7 @@ impl<'n, 'e> Clone for OptBuilder<'n, 'e> {
             name: self.name,
             short: self.short,
             long: self.long,
+            aliases: self.aliases.clone(),
             help: self.help,
             blacklist: self.blacklist.clone(),
             overrides: self.overrides.clone(),
@@ -252,7 +271,19 @@ impl<'n, 'e> AnyArg<'n, 'e> for OptBuilder<'n, 'e> {
         true
     }
     fn aliases(&self) -> Option<Vec<&'e str>> {
-        None
+        if let Some(ref aliases) = self.aliases {
+            let vis_aliases: Vec<_> =
+                aliases.iter()
+                    .filter_map(|&(n, v)| if v { Some(n) } else { None })
+                    .collect();
+            if vis_aliases.is_empty() {
+                None
+            } else {
+                Some(vis_aliases)
+            }
+        } else {
+            None
+        }
     }
 }
 
@@ -303,4 +334,25 @@ mod test {
 
         assert_eq!(&*format!("{}", o2), "-o <file> <name>");
     }
+
+    #[test]
+    fn optbuilder_display_single_alias() {
+        let mut o = OptBuilder::new("opt");
+        o.long = Some("option");
+        o.aliases = Some(vec![("als", true)]);
+
+        assert_eq!(&*format!("{}", o), "--option <opt> [aliases: als]");
+    }
+
+    fn optbuilder_display_multiple_aliases() {
+        let mut o = OptBuilder::new("opt");
+        o.long = Some("option");
+        o.aliases = Some(vec![
+                         ("als_not_visible", false),
+                         ("als2", true),
+                         ("als3", true),
+                         ("als4", true)
+                    ]);
+        assert_eq!(&*format!("{}", o), "--option <opt> [aliases: als2, als3, als4]");
+    }
 }

tests/app.yml

@@ -64,6 +64,14 @@ args:
         help: Tests mutliple values with required delimiter
         multiple: true
         require_delimiter: true
+    - singlealias:
+        long: singlealias
+        help: Tests single alias
+        aliases: [alias]
+    - multaliases:
+        long: multaliases
+        help: Tests mutliple aliases
+        aliases: [als1, als2, als3]
     - minvals2:
         long: minvals2
         multiple: true