Add structopt dependency in version 0.3.7

This patch series replaces argparse with structopt in the argument
handling code. As a first step, we need structopt as a dependency.

Import subrepo structopt/:structopt at efbdda4753592e27bc430fb01f7b9650b2f3174d
Import subrepo bitflags/:bitflags at 30668016aca6bd3b02c766e8347e0b4080d4c296
Import subrepo clap/:clap at 784524f7eb193e35f81082cc69454c8c21b948f7
Import subrepo heck/:heck at 093d56fbf001e1506e56dbfa38631d99b1066df1
Import subrepo proc-macro-error/:proc-macro-error at 6c4cfe79a622c5de8ae68557993542be46eacae2
Import subrepo proc-macro2/:proc-macro2 at d5d48eddca4566e5438e8a2cbed4a74e049544de
Import subrepo quote/:quote at 727436c6c137b20f0f34dde5d8fda2679b9747ad
Import subrepo rustversion/:rustversion at 0c5663313516263059ce9059ef81fc7a1cf655ca
Import subrepo syn-mid/:syn-mid at 5d3d85414a9e6674e1857ec22a87b96e04a6851a
Import subrepo syn/:syn at e87c27e87f6f4ef8919d0372bdb056d53ef0d8f3
Import subrepo textwrap/:textwrap at abcd618beae3f74841032aa5b53c1086b0a57ca2
Import subrepo unicode-segmentation/:unicode-segmentation at 637c9874c4fe0c205ff27787faf150a40295c6c3
Import subrepo unicode-width/:unicode-width at 3033826f8bf05e82724140a981d5941e48fce393
Import subrepo unicode-xid/:unicode-xid at 4baae9fffb156ba229665b972a9cd5991787ceb7

8 files changed, 1314 insertions, 0 deletions

diff --git a/clap/src/completions/bash.rs b/clap/src/completions/bash.rs
new file mode 100644
index 0000000..37dfa66
--- /dev/null
+++ b/clap/src/completions/bash.rs
@@ -0,0 +1,219 @@
+// Std
+use std::io::Write;
+
+// Internal
+use app::parser::Parser;
+use args::OptBuilder;
+use completions;
+
+pub struct BashGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> BashGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self { BashGen { p: p } }
+
+    pub fn generate_to<W: Write>(&self, buf: &mut W) {
+        w!(
+            buf,
+            format!(
+                r#"_{name}() {{
+    local i cur prev opts cmds
+    COMPREPLY=()
+    cur="${{COMP_WORDS[COMP_CWORD]}}"
+    prev="${{COMP_WORDS[COMP_CWORD-1]}}"
+    cmd=""
+    opts=""
+
+    for i in ${{COMP_WORDS[@]}}
+    do
+        case "${{i}}" in
+            {name})
+                cmd="{name}"
+                ;;
+            {subcmds}
+            *)
+                ;;
+        esac
+    done
+
+    case "${{cmd}}" in
+        {name})
+            opts="{name_opts}"
+            if [[ ${{cur}} == -* || ${{COMP_CWORD}} -eq 1 ]] ; then
+                COMPREPLY=( $(compgen -W "${{opts}}" -- "${{cur}}") )
+                return 0
+            fi
+            case "${{prev}}" in
+                {name_opts_details}
+                *)
+                    COMPREPLY=()
+                    ;;
+            esac
+            COMPREPLY=( $(compgen -W "${{opts}}" -- "${{cur}}") )
+            return 0
+            ;;
+        {subcmd_details}
+    esac
+}}
+
+complete -F _{name} -o bashdefault -o default {name}
+"#,
+                name = self.p.meta.bin_name.as_ref().unwrap(),
+                name_opts = self.all_options_for_path(self.p.meta.bin_name.as_ref().unwrap()),
+                name_opts_details =
+                    self.option_details_for_path(self.p.meta.bin_name.as_ref().unwrap()),
+                subcmds = self.all_subcommands(),
+                subcmd_details = self.subcommand_details()
+            ).as_bytes()
+        );
+    }
+
+    fn all_subcommands(&self) -> String {
+        debugln!("BashGen::all_subcommands;");
+        let mut subcmds = String::new();
+        let scs = completions::all_subcommand_names(self.p);
+
+        for sc in &scs {
+            subcmds = format!(
+                r#"{}
+            {name})
+                cmd+="__{fn_name}"
+                ;;"#,
+                subcmds,
+                name = sc,
+                fn_name = sc.replace("-", "__")
+            );
+        }
+
+        subcmds
+    }
+
+    fn subcommand_details(&self) -> String {
+        debugln!("BashGen::subcommand_details;");
+        let mut subcmd_dets = String::new();
+        let mut scs = completions::get_all_subcommand_paths(self.p, true);
+        scs.sort();
+        scs.dedup();
+
+        for sc in &scs {
+            subcmd_dets = format!(
+                r#"{}
+        {subcmd})
+            opts="{sc_opts}"
+            if [[ ${{cur}} == -* || ${{COMP_CWORD}} -eq {level} ]] ; then
+                COMPREPLY=( $(compgen -W "${{opts}}" -- "${{cur}}") )
+                return 0
+            fi
+            case "${{prev}}" in
+                {opts_details}
+                *)
+                    COMPREPLY=()
+                    ;;
+            esac
+            COMPREPLY=( $(compgen -W "${{opts}}" -- "${{cur}}") )
+            return 0
+            ;;"#,
+                subcmd_dets,
+                subcmd = sc.replace("-", "__"),
+                sc_opts = self.all_options_for_path(&*sc),
+                level = sc.split("__").map(|_| 1).fold(0, |acc, n| acc + n),
+                opts_details = self.option_details_for_path(&*sc)
+            );
+        }
+
+        subcmd_dets
+    }
+
+    fn option_details_for_path(&self, path: &str) -> String {
+        debugln!("BashGen::option_details_for_path: path={}", path);
+        let mut p = self.p;
+        for sc in path.split("__").skip(1) {
+            debugln!("BashGen::option_details_for_path:iter: sc={}", sc);
+            p = &find_subcmd!(p, sc).unwrap().p;
+        }
+        let mut opts = String::new();
+        for o in p.opts() {
+            if let Some(l) = o.s.long {
+                opts = format!(
+                    "{}
+                --{})
+                    COMPREPLY=({})
+                    return 0
+                    ;;",
+                    opts,
+                    l,
+                    self.vals_for(o)
+                );
+            }
+            if let Some(s) = o.s.short {
+                opts = format!(
+                    "{}
+                    -{})
+                    COMPREPLY=({})
+                    return 0
+                    ;;",
+                    opts,
+                    s,
+                    self.vals_for(o)
+                );
+            }
+        }
+        opts
+    }
+
+    fn vals_for(&self, o: &OptBuilder) -> String {
+        debugln!("BashGen::vals_for: o={}", o.b.name);
+        use args::AnyArg;
+        if let Some(vals) = o.possible_vals() {
+            format!(r#"$(compgen -W "{}" -- "${{cur}}")"#, vals.join(" "))
+        } else {
+            String::from(r#"$(compgen -f "${cur}")"#)
+        }
+    }
+
+    fn all_options_for_path(&self, path: &str) -> String {
+        debugln!("BashGen::all_options_for_path: path={}", path);
+        let mut p = self.p;
+        for sc in path.split("__").skip(1) {
+            debugln!("BashGen::all_options_for_path:iter: sc={}", sc);
+            p = &find_subcmd!(p, sc).unwrap().p;
+        }
+        let mut opts = shorts!(p).fold(String::new(), |acc, s| format!("{} -{}", acc, s));
+        opts = format!(
+            "{} {}",
+            opts,
+            longs!(p).fold(String::new(), |acc, l| format!("{} --{}", acc, l))
+        );
+        opts = format!(
+            "{} {}",
+            opts,
+            p.positionals
+                .values()
+                .fold(String::new(), |acc, p| format!("{} {}", acc, p))
+        );
+        opts = format!(
+            "{} {}",
+            opts,
+            p.subcommands
+                .iter()
+                .fold(String::new(), |acc, s| format!("{} {}", acc, s.p.meta.name))
+        );
+        for sc in &p.subcommands {
+            if let Some(ref aliases) = sc.p.meta.aliases {
+                opts = format!(
+                    "{} {}",
+                    opts,
+                    aliases
+                        .iter()
+                        .map(|&(n, _)| n)
+                        .fold(String::new(), |acc, a| format!("{} {}", acc, a))
+                );
+            }
+        }
+        opts
+    }
+}
diff --git a/clap/src/completions/elvish.rs b/clap/src/completions/elvish.rs
new file mode 100644
index 0000000..9a5f21a
--- /dev/null
+++ b/clap/src/completions/elvish.rs
@@ -0,0 +1,126 @@
+// Std
+use std::io::Write;
+
+// Internal
+use app::parser::Parser;
+use INTERNAL_ERROR_MSG;
+
+pub struct ElvishGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> ElvishGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self { ElvishGen { p: p } }
+
+    pub fn generate_to<W: Write>(&self, buf: &mut W) {
+        let bin_name = self.p.meta.bin_name.as_ref().unwrap();
+
+        let mut names = vec![];
+        let subcommands_cases =
+            generate_inner(self.p, "", &mut names);
+
+        let result = format!(r#"
+edit:completion:arg-completer[{bin_name}] = [@words]{{
+    fn spaces [n]{{
+        repeat $n ' ' | joins ''
+    }}
+    fn cand [text desc]{{
+        edit:complex-candidate $text &display-suffix=' '(spaces (- 14 (wcswidth $text)))$desc
+    }}
+    command = '{bin_name}'
+    for word $words[1:-1] {{
+        if (has-prefix $word '-') {{
+            break
+        }}
+        command = $command';'$word
+    }}
+    completions = [{subcommands_cases}
+    ]
+    $completions[$command]
+}}
+"#,
+            bin_name = bin_name,
+            subcommands_cases = subcommands_cases
+        );
+
+        w!(buf, result.as_bytes());
+    }
+}
+
+// Escape string inside single quotes
+fn escape_string(string: &str) -> String { string.replace("'", "''") }
+
+fn get_tooltip<T : ToString>(help: Option<&str>, data: T) -> String {
+    match help {
+        Some(help) => escape_string(help),
+        _ => data.to_string()
+    }
+}
+
+fn generate_inner<'a, 'b, 'p>(
+    p: &'p Parser<'a, 'b>,
+    previous_command_name: &str,
+    names: &mut Vec<&'p str>,
+) -> String {
+    debugln!("ElvishGen::generate_inner;");
+    let command_name = if previous_command_name.is_empty() {
+        p.meta.bin_name.as_ref().expect(INTERNAL_ERROR_MSG).clone()
+    } else {
+        format!("{};{}", previous_command_name, &p.meta.name)
+    };
+
+    let mut completions = String::new();
+    let preamble = String::from("\n            cand ");
+
+    for option in p.opts() {
+        if let Some(data) = option.s.short {
+            let tooltip = get_tooltip(option.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("-{} '{}'", data, tooltip).as_str());
+        }
+        if let Some(data) = option.s.long {
+            let tooltip = get_tooltip(option.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("--{} '{}'", data, tooltip).as_str());
+        }
+    }
+
+    for flag in p.flags() {
+        if let Some(data) = flag.s.short {
+            let tooltip = get_tooltip(flag.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("-{} '{}'", data, tooltip).as_str());
+        }
+        if let Some(data) = flag.s.long {
+            let tooltip = get_tooltip(flag.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("--{} '{}'", data, tooltip).as_str());
+        }
+    }
+
+    for subcommand in &p.subcommands {
+        let data = &subcommand.p.meta.name;
+        let tooltip = get_tooltip(subcommand.p.meta.about, data);
+        completions.push_str(&preamble);
+        completions.push_str(format!("{} '{}'", data, tooltip).as_str());
+    }
+
+    let mut subcommands_cases = format!(
+        r"
+        &'{}'= {{{}
+        }}",
+        &command_name,
+        completions
+    );
+
+    for subcommand in &p.subcommands {
+        let subcommand_subcommands_cases =
+            generate_inner(&subcommand.p, &command_name, names);
+        subcommands_cases.push_str(&subcommand_subcommands_cases);
+    }
+
+    subcommands_cases
+}
diff --git a/clap/src/completions/fish.rs b/clap/src/completions/fish.rs
new file mode 100644
index 0000000..c2c5a5e
--- /dev/null
+++ b/clap/src/completions/fish.rs
@@ -0,0 +1,99 @@
+// Std
+use std::io::Write;
+
+// Internal
+use app::parser::Parser;
+
+pub struct FishGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> FishGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self { FishGen { p: p } }
+
+    pub fn generate_to<W: Write>(&self, buf: &mut W) {
+        let command = self.p.meta.bin_name.as_ref().unwrap();
+        let mut buffer = String::new();
+        gen_fish_inner(command, self, command, &mut buffer);
+        w!(buf, buffer.as_bytes());
+    }
+}
+
+// Escape string inside single quotes
+fn escape_string(string: &str) -> String { string.replace("\\", "\\\\").replace("'", "\\'") }
+
+fn gen_fish_inner(root_command: &str, comp_gen: &FishGen, subcommand: &str, buffer: &mut String) {
+    debugln!("FishGen::gen_fish_inner;");
+    // example :
+    //
+    // complete
+    //      -c {command}
+    //      -d "{description}"
+    //      -s {short}
+    //      -l {long}
+    //      -a "{possible_arguments}"
+    //      -r # if require parameter
+    //      -f # don't use file completion
+    //      -n "__fish_use_subcommand"               # complete for command "myprog"
+    //      -n "__fish_seen_subcommand_from subcmd1" # complete for command "myprog subcmd1"
+
+    let mut basic_template = format!("complete -c {} -n ", root_command);
+    if root_command == subcommand {
+        basic_template.push_str("\"__fish_use_subcommand\"");
+    } else {
+        basic_template.push_str(format!("\"__fish_seen_subcommand_from {}\"", subcommand).as_str());
+    }
+
+    for option in comp_gen.p.opts() {
+        let mut template = basic_template.clone();
+        if let Some(data) = option.s.short {
+            template.push_str(format!(" -s {}", data).as_str());
+        }
+        if let Some(data) = option.s.long {
+            template.push_str(format!(" -l {}", data).as_str());
+        }
+        if let Some(data) = option.b.help {
+            template.push_str(format!(" -d '{}'", escape_string(data)).as_str());
+        }
+        if let Some(ref data) = option.v.possible_vals {
+            template.push_str(format!(" -r -f -a \"{}\"", data.join(" ")).as_str());
+        }
+        buffer.push_str(template.as_str());
+        buffer.push_str("\n");
+    }
+
+    for flag in comp_gen.p.flags() {
+        let mut template = basic_template.clone();
+        if let Some(data) = flag.s.short {
+            template.push_str(format!(" -s {}", data).as_str());
+        }
+        if let Some(data) = flag.s.long {
+            template.push_str(format!(" -l {}", data).as_str());
+        }
+        if let Some(data) = flag.b.help {
+            template.push_str(format!(" -d '{}'", escape_string(data)).as_str());
+        }
+        buffer.push_str(template.as_str());
+        buffer.push_str("\n");
+    }
+
+    for subcommand in &comp_gen.p.subcommands {
+        let mut template = basic_template.clone();
+        template.push_str(" -f");
+        template.push_str(format!(" -a \"{}\"", &subcommand.p.meta.name).as_str());
+        if let Some(data) = subcommand.p.meta.about {
+            template.push_str(format!(" -d '{}'", escape_string(data)).as_str())
+        }
+        buffer.push_str(template.as_str());
+        buffer.push_str("\n");
+    }
+
+    // generate options of subcommands
+    for subcommand in &comp_gen.p.subcommands {
+        let sub_comp_gen = FishGen::new(&subcommand.p);
+        gen_fish_inner(root_command, &sub_comp_gen, &subcommand.to_string(), buffer);
+    }
+}
diff --git a/clap/src/completions/macros.rs b/clap/src/completions/macros.rs
new file mode 100644
index 0000000..653c72c
--- /dev/null
+++ b/clap/src/completions/macros.rs
@@ -0,0 +1,28 @@
+macro_rules! w {
+    ($buf:expr, $to_w:expr) => {
+        match $buf.write_all($to_w) {
+            Ok(..) => (),
+            Err(..) => panic!("Failed to write to completions file"),
+        }
+    };
+}
+
+macro_rules! get_zsh_arg_conflicts {
+    ($p:ident, $arg:ident, $msg:ident) => {
+        if let Some(conf_vec) = $arg.blacklist() {
+            let mut v = vec![];
+            for arg_name in conf_vec {
+                let arg = $p.find_any_arg(arg_name).expect($msg);
+                if let Some(s) = arg.short() {
+                    v.push(format!("-{}", s));
+                }
+                if let Some(l) = arg.long() {
+                    v.push(format!("--{}", l));
+                }
+            }
+            v.join(" ")
+        } else {
+            String::new()
+        }
+    }
+}
diff --git a/clap/src/completions/mod.rs b/clap/src/completions/mod.rs
new file mode 100644
index 0000000..a3306d7
--- /dev/null
+++ b/clap/src/completions/mod.rs
@@ -0,0 +1,179 @@
+#[macro_use]
+mod macros;
+mod bash;
+mod fish;
+mod zsh;
+mod powershell;
+mod elvish;
+mod shell;
+
+// Std
+use std::io::Write;
+
+// Internal
+use app::parser::Parser;
+use self::bash::BashGen;
+use self::fish::FishGen;
+use self::zsh::ZshGen;
+use self::powershell::PowerShellGen;
+use self::elvish::ElvishGen;
+pub use self::shell::Shell;
+
+pub struct ComplGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> ComplGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self { ComplGen { p: p } }
+
+    pub fn generate<W: Write>(&self, for_shell: Shell, buf: &mut W) {
+        match for_shell {
+            Shell::Bash => BashGen::new(self.p).generate_to(buf),
+            Shell::Fish => FishGen::new(self.p).generate_to(buf),
+            Shell::Zsh => ZshGen::new(self.p).generate_to(buf),
+            Shell::PowerShell => PowerShellGen::new(self.p).generate_to(buf),
+            Shell::Elvish => ElvishGen::new(self.p).generate_to(buf),
+        }
+    }
+}
+
+// Gets all subcommands including child subcommands in the form of 'name' where the name
+// is a single word (i.e. "install")  of the path to said subcommand (i.e.
+// "rustup toolchain install")
+//
+// Also note, aliases are treated as their own subcommands but duplicates of whatever they're
+// aliasing.
+pub fn all_subcommand_names(p: &Parser) -> Vec<String> {
+    debugln!("all_subcommand_names;");
+    let mut subcmds: Vec<_> = subcommands_of(p)
+        .iter()
+        .map(|&(ref n, _)| n.clone())
+        .collect();
+    for sc_v in p.subcommands.iter().map(|s| all_subcommand_names(&s.p)) {
+        subcmds.extend(sc_v);
+    }
+    subcmds.sort();
+    subcmds.dedup();
+    subcmds
+}
+
+// Gets all subcommands including child subcommands in the form of ('name', 'bin_name') where the name
+// is a single word (i.e. "install") of the path and full bin_name of said subcommand (i.e.
+// "rustup toolchain install")
+//
+// Also note, aliases are treated as their own subcommands but duplicates of whatever they're
+// aliasing.
+pub fn all_subcommands(p: &Parser) -> Vec<(String, String)> {
+    debugln!("all_subcommands;");
+    let mut subcmds: Vec<_> = subcommands_of(p);
+    for sc_v in p.subcommands.iter().map(|s| all_subcommands(&s.p)) {
+        subcmds.extend(sc_v);
+    }
+    subcmds
+}
+
+// Gets all subcommands excluding child subcommands in the form of (name, bin_name) where the name
+// is a single word (i.e. "install") and the bin_name is a space delineated list of the path to said
+// subcommand (i.e. "rustup toolchain install")
+//
+// Also note, aliases are treated as their own subcommands but duplicates of whatever they're
+// aliasing.
+pub fn subcommands_of(p: &Parser) -> Vec<(String, String)> {
+    debugln!(
+        "subcommands_of: name={}, bin_name={}",
+        p.meta.name,
+        p.meta.bin_name.as_ref().unwrap()
+    );
+    let mut subcmds = vec![];
+
+    debugln!(
+        "subcommands_of: Has subcommands...{:?}",
+        p.has_subcommands()
+    );
+    if !p.has_subcommands() {
+        let mut ret = vec![];
+        debugln!("subcommands_of: Looking for aliases...");
+        if let Some(ref aliases) = p.meta.aliases {
+            for &(n, _) in aliases {
+                debugln!("subcommands_of:iter:iter: Found alias...{}", n);
+                let mut als_bin_name: Vec<_> =
+                    p.meta.bin_name.as_ref().unwrap().split(' ').collect();
+                als_bin_name.push(n);
+                let old = als_bin_name.len() - 2;
+                als_bin_name.swap_remove(old);
+                ret.push((n.to_owned(), als_bin_name.join(" ")));
+            }
+        }
+        return ret;
+    }
+    for sc in &p.subcommands {
+        debugln!(
+            "subcommands_of:iter: name={}, bin_name={}",
+            sc.p.meta.name,
+            sc.p.meta.bin_name.as_ref().unwrap()
+        );
+
+        debugln!("subcommands_of:iter: Looking for aliases...");
+        if let Some(ref aliases) = sc.p.meta.aliases {
+            for &(n, _) in aliases {
+                debugln!("subcommands_of:iter:iter: Found alias...{}", n);
+                let mut als_bin_name: Vec<_> =
+                    p.meta.bin_name.as_ref().unwrap().split(' ').collect();
+                als_bin_name.push(n);
+                let old = als_bin_name.len() - 2;
+                als_bin_name.swap_remove(old);
+                subcmds.push((n.to_owned(), als_bin_name.join(" ")));
+            }
+        }
+        subcmds.push((
+            sc.p.meta.name.clone(),
+            sc.p.meta.bin_name.as_ref().unwrap().clone(),
+        ));
+    }
+    subcmds
+}
+
+pub fn get_all_subcommand_paths(p: &Parser, first: bool) -> Vec<String> {
+    debugln!("get_all_subcommand_paths;");
+    let mut subcmds = vec![];
+    if !p.has_subcommands() {
+        if !first {
+            let name = &*p.meta.name;
+            let path = p.meta.bin_name.as_ref().unwrap().clone().replace(" ", "__");
+            let mut ret = vec![path.clone()];
+            if let Some(ref aliases) = p.meta.aliases {
+                for &(n, _) in aliases {
+                    ret.push(path.replace(name, n));
+                }
+            }
+            return ret;
+        }
+        return vec![];
+    }
+    for sc in &p.subcommands {
+        let name = &*sc.p.meta.name;
+        let path = sc.p
+            .meta
+            .bin_name
+            .as_ref()
+            .unwrap()
+            .clone()
+            .replace(" ", "__");
+        subcmds.push(path.clone());
+        if let Some(ref aliases) = sc.p.meta.aliases {
+            for &(n, _) in aliases {
+                subcmds.push(path.replace(name, n));
+            }
+        }
+    }
+    for sc_v in p.subcommands
+        .iter()
+        .map(|s| get_all_subcommand_paths(&s.p, false))
+    {
+        subcmds.extend(sc_v);
+    }
+    subcmds
+}
diff --git a/clap/src/completions/powershell.rs b/clap/src/completions/powershell.rs
new file mode 100644
index 0000000..9fc77c7
--- /dev/null
+++ b/clap/src/completions/powershell.rs
@@ -0,0 +1,139 @@
+// Std
+use std::io::Write;
+
+// Internal
+use app::parser::Parser;
+use INTERNAL_ERROR_MSG;
+
+pub struct PowerShellGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> PowerShellGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self { PowerShellGen { p: p } }
+
+    pub fn generate_to<W: Write>(&self, buf: &mut W) {
+        let bin_name = self.p.meta.bin_name.as_ref().unwrap();
+
+        let mut names = vec![];
+        let subcommands_cases =
+            generate_inner(self.p, "", &mut names);
+
+        let result = format!(r#"
+using namespace System.Management.Automation
+using namespace System.Management.Automation.Language
+
+Register-ArgumentCompleter -Native -CommandName '{bin_name}' -ScriptBlock {{
+    param($wordToComplete, $commandAst, $cursorPosition)
+
+    $commandElements = $commandAst.CommandElements
+    $command = @(
+        '{bin_name}'
+        for ($i = 1; $i -lt $commandElements.Count; $i++) {{
+            $element = $commandElements[$i]
+            if ($element -isnot [StringConstantExpressionAst] -or
+                $element.StringConstantType -ne [StringConstantType]::BareWord -or
+                $element.Value.StartsWith('-')) {{
+                break
+        }}
+        $element.Value
+    }}) -join ';'
+
+    $completions = @(switch ($command) {{{subcommands_cases}
+    }})
+
+    $completions.Where{{ $_.CompletionText -like "$wordToComplete*" }} |
+        Sort-Object -Property ListItemText
+}}
+"#,
+            bin_name = bin_name,
+            subcommands_cases = subcommands_cases
+        );
+
+        w!(buf, result.as_bytes());
+    }
+}
+
+// Escape string inside single quotes
+fn escape_string(string: &str) -> String { string.replace("'", "''") }
+
+fn get_tooltip<T : ToString>(help: Option<&str>, data: T) -> String {
+    match help {
+        Some(help) => escape_string(help),
+        _ => data.to_string()
+    }
+}
+
+fn generate_inner<'a, 'b, 'p>(
+    p: &'p Parser<'a, 'b>,
+    previous_command_name: &str,
+    names: &mut Vec<&'p str>,
+) -> String {
+    debugln!("PowerShellGen::generate_inner;");
+    let command_name = if previous_command_name.is_empty() {
+        p.meta.bin_name.as_ref().expect(INTERNAL_ERROR_MSG).clone()
+    } else {
+        format!("{};{}", previous_command_name, &p.meta.name)
+    };
+
+    let mut completions = String::new();
+    let preamble = String::from("\n            [CompletionResult]::new(");
+
+    for option in p.opts() {
+        if let Some(data) = option.s.short {
+            let tooltip = get_tooltip(option.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("'-{}', '{}', {}, '{}')",
+                                         data, data, "[CompletionResultType]::ParameterName", tooltip).as_str());
+        }
+        if let Some(data) = option.s.long {
+            let tooltip = get_tooltip(option.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("'--{}', '{}', {}, '{}')",
+                                         data, data, "[CompletionResultType]::ParameterName", tooltip).as_str());
+        }
+    }
+
+    for flag in p.flags() {
+        if let Some(data) = flag.s.short {
+            let tooltip = get_tooltip(flag.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("'-{}', '{}', {}, '{}')",
+                                         data, data, "[CompletionResultType]::ParameterName", tooltip).as_str());
+        }
+        if let Some(data) = flag.s.long {
+            let tooltip = get_tooltip(flag.b.help, data);
+            completions.push_str(&preamble);
+            completions.push_str(format!("'--{}', '{}', {}, '{}')",
+                                         data, data, "[CompletionResultType]::ParameterName", tooltip).as_str());
+        }
+    }
+
+    for subcommand in &p.subcommands {
+        let data = &subcommand.p.meta.name;
+        let tooltip = get_tooltip(subcommand.p.meta.about, data);
+        completions.push_str(&preamble);
+        completions.push_str(format!("'{}', '{}', {}, '{}')",
+                                     data, data, "[CompletionResultType]::ParameterValue", tooltip).as_str());
+    }
+
+    let mut subcommands_cases = format!(
+        r"
+        '{}' {{{}
+            break
+        }}",
+        &command_name,
+        completions
+    );
+
+    for subcommand in &p.subcommands {
+        let subcommand_subcommands_cases =
+            generate_inner(&subcommand.p, &command_name, names);
+        subcommands_cases.push_str(&subcommand_subcommands_cases);
+    }
+
+    subcommands_cases
+}
diff --git a/clap/src/completions/shell.rs b/clap/src/completions/shell.rs
new file mode 100644
index 0000000..19aab86
--- /dev/null
+++ b/clap/src/completions/shell.rs
@@ -0,0 +1,52 @@
+#[allow(deprecated, unused_imports)]
+use std::ascii::AsciiExt;
+use std::str::FromStr;
+use std::fmt;
+
+/// Describes which shell to produce a completions file for
+#[cfg_attr(feature = "lints", allow(enum_variant_names))]
+#[derive(Debug, Copy, Clone)]
+pub enum Shell {
+    /// Generates a .bash completion file for the Bourne Again SHell (BASH)
+    Bash,
+    /// Generates a .fish completion file for the Friendly Interactive SHell (fish)
+    Fish,
+    /// Generates a completion file for the Z SHell (ZSH)
+    Zsh,
+    /// Generates a completion file for PowerShell
+    PowerShell,
+    /// Generates a completion file for Elvish
+    Elvish,
+}
+
+impl Shell {
+    /// A list of possible variants in `&'static str` form
+    pub fn variants() -> [&'static str; 5] { ["zsh", "bash", "fish", "powershell", "elvish"] }
+}
+
+impl FromStr for Shell {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "ZSH" | _ if s.eq_ignore_ascii_case("zsh") => Ok(Shell::Zsh),
+            "FISH" | _ if s.eq_ignore_ascii_case("fish") => Ok(Shell::Fish),
+            "BASH" | _ if s.eq_ignore_ascii_case("bash") => Ok(Shell::Bash),
+            "POWERSHELL" | _ if s.eq_ignore_ascii_case("powershell") => Ok(Shell::PowerShell),
+            "ELVISH" | _ if s.eq_ignore_ascii_case("elvish") => Ok(Shell::Elvish),
+            _ => Err(String::from("[valid values: bash, fish, zsh, powershell, elvish]")),
+        }
+    }
+}
+
+impl fmt::Display for Shell {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Shell::Bash => write!(f, "BASH"),
+            Shell::Fish => write!(f, "FISH"),
+            Shell::Zsh => write!(f, "ZSH"),
+            Shell::PowerShell => write!(f, "POWERSHELL"),
+            Shell::Elvish => write!(f, "ELVISH"),
+        }
+    }
+}
diff --git a/clap/src/completions/zsh.rs b/clap/src/completions/zsh.rs
new file mode 100644
index 0000000..5d23fd2
--- /dev/null
+++ b/clap/src/completions/zsh.rs
@@ -0,0 +1,472 @@
+// Std
+use std::io::Write;
+#[allow(deprecated, unused_imports)]
+use std::ascii::AsciiExt;
+
+// Internal
+use app::App;
+use app::parser::Parser;
+use args::{AnyArg, ArgSettings};
+use completions;
+use INTERNAL_ERROR_MSG;
+
+pub struct ZshGen<'a, 'b>
+where
+    'a: 'b,
+{
+    p: &'b Parser<'a, 'b>,
+}
+
+impl<'a, 'b> ZshGen<'a, 'b> {
+    pub fn new(p: &'b Parser<'a, 'b>) -> Self {
+        debugln!("ZshGen::new;");
+        ZshGen { p: p }
+    }
+
+    pub fn generate_to<W: Write>(&self, buf: &mut W) {
+        debugln!("ZshGen::generate_to;");
+        w!(
+            buf,
+            format!(
+                "\
+#compdef {name}
+
+autoload -U is-at-least
+
+_{name}() {{
+    typeset -A opt_args
+    typeset -a _arguments_options
+    local ret=1
+
+    if is-at-least 5.2; then
+        _arguments_options=(-s -S -C)
+    else
+        _arguments_options=(-s -C)
+    fi
+
+    local context curcontext=\"$curcontext\" state line
+    {initial_args}
+    {subcommands}
+}}
+
+{subcommand_details}
+
+_{name} \"$@\"",
+                name = self.p.meta.bin_name.as_ref().unwrap(),
+                initial_args = get_args_of(self.p),
+                subcommands = get_subcommands_of(self.p),
+                subcommand_details = subcommand_details(self.p)
+            ).as_bytes()
+        );
+    }
+}
+
+// Displays the commands of a subcommand
+// (( $+functions[_[bin_name_underscore]_commands] )) ||
+// _[bin_name_underscore]_commands() {
+// 	local commands; commands=(
+// 		'[arg_name]:[arg_help]'
+// 	)
+// 	_describe -t commands '[bin_name] commands' commands "$@"
+//
+// Where the following variables are present:
+//    [bin_name_underscore]: The full space delineated bin_name, where spaces have been replaced by
+//                           underscore characters
+//    [arg_name]: The name of the subcommand
+//    [arg_help]: The help message of the subcommand
+//    [bin_name]: The full space delineated bin_name
+//
+// Here's a snippet from rustup:
+//
+// (( $+functions[_rustup_commands] )) ||
+// _rustup_commands() {
+// 	local commands; commands=(
+// 		'show:Show the active and installed toolchains'
+//      'update:Update Rust toolchains'
+//      # ... snip for brevity
+//      'help:Prints this message or the help of the given subcommand(s)'
+// 	)
+// 	_describe -t commands 'rustup commands' commands "$@"
+//
+fn subcommand_details(p: &Parser) -> String {
+    debugln!("ZshGen::subcommand_details;");
+    // First we do ourself
+    let mut ret = vec![
+        format!(
+            "\
+(( $+functions[_{bin_name_underscore}_commands] )) ||
+_{bin_name_underscore}_commands() {{
+    local commands; commands=(
+        {subcommands_and_args}
+    )
+    _describe -t commands '{bin_name} commands' commands \"$@\"
+}}",
+            bin_name_underscore = p.meta.bin_name.as_ref().unwrap().replace(" ", "__"),
+            bin_name = p.meta.bin_name.as_ref().unwrap(),
+            subcommands_and_args = subcommands_of(p)
+        ),
+    ];
+
+    // Next we start looping through all the children, grandchildren, etc.
+    let mut all_subcommands = completions::all_subcommands(p);
+    all_subcommands.sort();
+    all_subcommands.dedup();
+    for &(_, ref bin_name) in &all_subcommands {
+        debugln!("ZshGen::subcommand_details:iter: bin_name={}", bin_name);
+        ret.push(format!(
+            "\
+(( $+functions[_{bin_name_underscore}_commands] )) ||
+_{bin_name_underscore}_commands() {{
+    local commands; commands=(
+        {subcommands_and_args}
+    )
+    _describe -t commands '{bin_name} commands' commands \"$@\"
+}}",
+            bin_name_underscore = bin_name.replace(" ", "__"),
+            bin_name = bin_name,
+            subcommands_and_args = subcommands_of(parser_of(p, bin_name))
+        ));
+    }
+
+    ret.join("\n")
+}
+
+// Generates subcommand completions in form of
+//
+// 		'[arg_name]:[arg_help]'
+//
+// Where:
+//    [arg_name]: the subcommand's name
+//    [arg_help]: the help message of the subcommand
+//
+// A snippet from rustup:
+// 		'show:Show the active and installed toolchains'
+//      'update:Update Rust toolchains'
+fn subcommands_of(p: &Parser) -> String {
+    debugln!("ZshGen::subcommands_of;");
+    let mut ret = vec![];
+    fn add_sc(sc: &App, n: &str, ret: &mut Vec<String>) {
+        debugln!("ZshGen::add_sc;");
+        let s = format!(
+            "\"{name}:{help}\" \\",
+            name = n,
+            help = sc.p
+                .meta
+                .about
+                .unwrap_or("")
+                .replace("[", "\\[")
+                .replace("]", "\\]")
+        );
+        if !s.is_empty() {
+            ret.push(s);
+        }
+    }
+
+    // The subcommands
+    for sc in p.subcommands() {
+        debugln!(
+            "ZshGen::subcommands_of:iter: subcommand={}",
+            sc.p.meta.name
+        );
+        add_sc(sc, &sc.p.meta.name, &mut ret);
+        if let Some(ref v) = sc.p.meta.aliases {
+            for alias in v.iter().filter(|&&(_, vis)| vis).map(|&(n, _)| n) {
+                add_sc(sc, alias, &mut ret);
+            }
+        }
+    }
+
+    ret.join("\n")
+}
+
+// Get's the subcommand section of a completion file
+// This looks roughly like:
+//
+// case $state in
+// ([bin_name]_args)
+//     curcontext=\"${curcontext%:*:*}:[name_hyphen]-command-$words[1]:\"
+//     case $line[1] in
+//
+//         ([name])
+//         _arguments -C -s -S \
+//             [subcommand_args]
+//         && ret=0
+//
+//         [RECURSIVE_CALLS]
+//
+//         ;;",
+//
+//         [repeat]
+//
+//     esac
+// ;;
+// esac",
+//
+// Where the following variables are present:
+//    [name] = The subcommand name in the form of "install" for "rustup toolchain install"
+//    [bin_name] = The full space delineated bin_name such as "rustup toolchain install"
+//    [name_hyphen] = The full space delineated bin_name, but replace spaces with hyphens
+//    [repeat] = From the same recursive calls, but for all subcommands
+//    [subcommand_args] = The same as zsh::get_args_of
+fn get_subcommands_of(p: &Parser) -> String {
+    debugln!("get_subcommands_of;");
+
+    debugln!(
+        "get_subcommands_of: Has subcommands...{:?}",
+        p.has_subcommands()
+    );
+    if !p.has_subcommands() {
+        return String::new();
+    }
+
+    let sc_names = completions::subcommands_of(p);
+
+    let mut subcmds = vec![];
+    for &(ref name, ref bin_name) in &sc_names {
+        let mut v = vec![format!("({})", name)];
+        let subcommand_args = get_args_of(parser_of(p, &*bin_name));
+        if !subcommand_args.is_empty() {
+            v.push(subcommand_args);
+        }
+        let subcommands = get_subcommands_of(parser_of(p, &*bin_name));
+        if !subcommands.is_empty() {
+            v.push(subcommands);
+        }
+        v.push(String::from(";;"));
+        subcmds.push(v.join("\n"));
+    }
+
+    format!(
+        "case $state in
+    ({name})
+        words=($line[{pos}] \"${{words[@]}}\")
+        (( CURRENT += 1 ))
+        curcontext=\"${{curcontext%:*:*}}:{name_hyphen}-command-$line[{pos}]:\"
+        case $line[{pos}] in
+            {subcommands}
+        esac
+    ;;
+esac",
+        name = p.meta.name,
+        name_hyphen = p.meta.bin_name.as_ref().unwrap().replace(" ", "-"),
+        subcommands = subcmds.join("\n"),
+        pos = p.positionals().len() + 1
+    )
+}
+
+fn parser_of<'a, 'b>(p: &'b Parser<'a, 'b>, sc: &str) -> &'b Parser<'a, 'b> {
+    debugln!("parser_of: sc={}", sc);
+    if sc == p.meta.bin_name.as_ref().unwrap_or(&String::new()) {
+        return p;
+    }
+    &p.find_subcommand(sc).expect(INTERNAL_ERROR_MSG).p
+}
+
+// Writes out the args section, which ends up being the flags, opts and postionals, and a jump to
+// another ZSH function if there are subcommands.
+// The structer works like this:
+//    ([conflicting_args]) [multiple] arg [takes_value] [[help]] [: :(possible_values)]
+//       ^-- list '-v -h'    ^--'*'          ^--'+'                   ^-- list 'one two three'
+//
+// An example from the rustup command:
+//
+// _arguments -C -s -S \
+// 		'(-h --help --verbose)-v[Enable verbose output]' \
+// 		'(-V -v --version --verbose --help)-h[Prints help information]' \
+//      # ... snip for brevity
+// 		':: :_rustup_commands' \    # <-- displays subcommands
+// 		'*::: :->rustup' \          # <-- displays subcommand args and child subcommands
+// 	&& ret=0
+//
+// The args used for _arguments are as follows:
+//    -C: modify the $context internal variable
+//    -s: Allow stacking of short args (i.e. -a -b -c => -abc)
+//    -S: Do not complete anything after '--' and treat those as argument values
+fn get_args_of(p: &Parser) -> String {
+    debugln!("get_args_of;");
+    let mut ret = vec![String::from("_arguments \"${_arguments_options[@]}\" \\")];
+    let opts = write_opts_of(p);
+    let flags = write_flags_of(p);
+    let positionals = write_positionals_of(p);
+    let sc_or_a = if p.has_subcommands() {
+        format!(
+            "\":: :_{name}_commands\" \\",
+            name = p.meta.bin_name.as_ref().unwrap().replace(" ", "__")
+        )
+    } else {
+        String::new()
+    };
+    let sc = if p.has_subcommands() {
+        format!("\"*::: :->{name}\" \\", name = p.meta.name)
+    } else {
+        String::new()
+    };
+
+    if !opts.is_empty() {
+        ret.push(opts);
+    }
+    if !flags.is_empty() {
+        ret.push(flags);
+    }
+    if !positionals.is_empty() {
+        ret.push(positionals);
+    }
+    if !sc_or_a.is_empty() {
+        ret.push(sc_or_a);
+    }
+    if !sc.is_empty() {
+        ret.push(sc);
+    }
+    ret.push(String::from("&& ret=0"));
+
+    ret.join("\n")
+}
+
+// Escape help string inside single quotes and brackets
+fn escape_help(string: &str) -> String {
+    string
+        .replace("\\", "\\\\")
+        .replace("'", "'\\''")
+        .replace("[", "\\[")
+        .replace("]", "\\]")
+}
+
+// Escape value string inside single quotes and parentheses
+fn escape_value(string: &str) -> String {
+    string
+        .replace("\\", "\\\\")
+        .replace("'", "'\\''")
+        .replace("(", "\\(")
+        .replace(")", "\\)")
+        .replace(" ", "\\ ")
+}
+
+fn write_opts_of(p: &Parser) -> String {
+    debugln!("write_opts_of;");
+    let mut ret = vec![];
+    for o in p.opts() {
+        debugln!("write_opts_of:iter: o={}", o.name());
+        let help = o.help().map_or(String::new(), escape_help);
+        let mut conflicts = get_zsh_arg_conflicts!(p, o, INTERNAL_ERROR_MSG);
+        conflicts = if conflicts.is_empty() {
+            String::new()
+        } else {
+            format!("({})", conflicts)
+        };
+
+        let multiple = if o.is_set(ArgSettings::Multiple) {
+            "*"
+        } else {
+            ""
+        };
+        let pv = if let Some(pv_vec) = o.possible_vals() {
+            format!(": :({})", pv_vec.iter().map(
+                |v| escape_value(*v)).collect::<Vec<String>>().join(" "))
+        } else {
+            String::new()
+        };
+        if let Some(short) = o.short() {
+            let s = format!(
+                "'{conflicts}{multiple}-{arg}+[{help}]{possible_values}' \\",
+                conflicts = conflicts,
+                multiple = multiple,
+                arg = short,
+                possible_values = pv,
+                help = help
+            );
+
+            debugln!("write_opts_of:iter: Wrote...{}", &*s);
+            ret.push(s);
+        }
+        if let Some(long) = o.long() {
+            let l = format!(
+                "'{conflicts}{multiple}--{arg}=[{help}]{possible_values}' \\",
+                conflicts = conflicts,
+                multiple = multiple,
+                arg = long,
+                possible_values = pv,
+                help = help
+            );
+
+            debugln!("write_opts_of:iter: Wrote...{}", &*l);
+            ret.push(l);
+        }
+    }
+
+    ret.join("\n")
+}
+
+fn write_flags_of(p: &Parser) -> String {
+    debugln!("write_flags_of;");
+    let mut ret = vec![];
+    for f in p.flags() {
+        debugln!("write_flags_of:iter: f={}", f.name());
+        let help = f.help().map_or(String::new(), escape_help);
+        let mut conflicts = get_zsh_arg_conflicts!(p, f, INTERNAL_ERROR_MSG);
+        conflicts = if conflicts.is_empty() {
+            String::new()
+        } else {
+            format!("({})", conflicts)
+        };
+
+        let multiple = if f.is_set(ArgSettings::Multiple) {
+            "*"
+        } else {
+            ""
+        };
+        if let Some(short) = f.short() {
+            let s = format!(
+                "'{conflicts}{multiple}-{arg}[{help}]' \\",
+                multiple = multiple,
+                conflicts = conflicts,
+                arg = short,
+                help = help
+            );
+
+            debugln!("write_flags_of:iter: Wrote...{}", &*s);
+            ret.push(s);
+        }
+
+        if let Some(long) = f.long() {
+            let l = format!(
+                "'{conflicts}{multiple}--{arg}[{help}]' \\",
+                conflicts = conflicts,
+                multiple = multiple,
+                arg = long,
+                help = help
+            );
+
+            debugln!("write_flags_of:iter: Wrote...{}", &*l);
+            ret.push(l);
+        }
+    }
+
+    ret.join("\n")
+}
+
+fn write_positionals_of(p: &Parser) -> String {
+    debugln!("write_positionals_of;");
+    let mut ret = vec![];
+    for arg in p.positionals() {
+        debugln!("write_positionals_of:iter: arg={}", arg.b.name);
+        let a = format!(
+            "'{optional}:{name}{help}:{action}' \\",
+            optional = if !arg.b.is_set(ArgSettings::Required) { ":" } else { "" },
+            name = arg.b.name,
+            help = arg.b
+                .help
+                .map_or("".to_owned(), |v| " -- ".to_owned() + v)
+                .replace("[", "\\[")
+                .replace("]", "\\]"),
+            action = arg.possible_vals().map_or("_files".to_owned(), |values| {
+                format!("({})",
+                    values.iter().map(|v| escape_value(*v)).collect::<Vec<String>>().join(" "))
+            })
+        );
+
+        debugln!("write_positionals_of:iter: Wrote...{}", a);
+        ret.push(a);
+    }
+
+    ret.join("\n")
+}