moss/cli: Add --generate-completions for zsh, fish, bash

Signed-off-by: Ikey Doherty <ikey@serpentos.com>

moss/src/cli/mod.rs

@@ -2,9 +2,13 @@
 //
 // SPDX-License-Identifier: MPL-2.0
 
-use std::{env, path::PathBuf};
+use std::{env, fs, io, path::Path, path::PathBuf};
 
 use clap::{Arg, ArgAction, Command};
+use clap_complete::{
+    generate_to,
+    shells::{Bash, Fish, Zsh},
+};
 use clap_mangen::Man;
 use moss::{installation, runtime, Installation};
 use thiserror::Error;
@@ -68,6 +72,14 @@ fn command() -> Command {
                 .value_name("DIR")
                 .hide(true),
         )
+        .arg(
+            Arg::new("generate-completions")
+                .long("generate-completions")
+                .help("Generate shell completions")
+                .action(ArgAction::Set)
+                .value_name("DIR")
+                .hide(true),
+        )
         .arg_required_else_help(true)
         .subcommand(extract::command())
         .subcommand(index::command())
@@ -84,7 +96,7 @@ fn command() -> Command {
 }
 
 /// Generate manpages for all commands recursively
-fn generate_manpages(cmd: &Command, dir: &std::path::Path, prefix: Option<&str>) -> std::io::Result<()> {
+fn generate_manpages(cmd: &Command, dir: &Path, prefix: Option<&str>) -> io::Result<()> {
     let name = cmd.get_name();
     let man = Man::new(cmd.to_owned());
     let mut buffer: Vec<u8> = Default::default();
@@ -96,7 +108,7 @@ fn generate_manpages(cmd: &Command, dir: &std::path::Path, prefix: Option<&str>)
         format!("{}.1", name)
     };
 
-    std::fs::write(dir.join(filename), buffer)?;
+    fs::write(dir.join(filename), buffer)?;
 
     for subcmd in cmd.get_subcommands() {
         let new_prefix = if let Some(p) = prefix {
@@ -109,18 +121,33 @@ fn generate_manpages(cmd: &Command, dir: &std::path::Path, prefix: Option<&str>)
     Ok(())
 }
 
+/// Generate shell completions
+fn generate_completions(cmd: &mut Command, dir: &Path) -> io::Result<()> {
+    generate_to(Bash, cmd, "moss", dir)?;
+    generate_to(Fish, cmd, "moss", dir)?;
+    generate_to(Zsh, cmd, "moss", dir)?;
+    Ok(())
+}
+
 /// Process all CLI arguments
 pub fn process() -> Result<(), Error> {
     let args = replace_aliases(env::args());
     let matches = command().get_matches_from(args);
 
     if let Some(dir) = matches.get_one::<String>("generate-manpages") {
-        let dir = std::path::Path::new(dir);
-        std::fs::create_dir_all(dir)?;
+        let dir = Path::new(dir);
+        fs::create_dir_all(dir)?;
         generate_manpages(&command(), dir, None)?;
         return Ok(());
     }
 
+    if let Some(dir) = matches.get_one::<String>("generate-completions") {
+        let dir = Path::new(dir);
+        fs::create_dir_all(dir)?;
+        generate_completions(&mut command(), dir)?;
+        return Ok(());
+    }
+
     // Print the version, but not if the user is using the version subcommand
     if matches.get_flag("verbose") {
         if let Some(command) = matches.subcommand_name() {
@@ -234,5 +261,5 @@ pub enum Error {
     Installation(#[from] installation::Error),
 
     #[error("I/O error: {0}")]
-    Io(#[from] std::io::Error),
+    Io(#[from] io::Error),
 }