feat(console): add subcommand for gen completions

tokio-console/Cargo.toml

@@ -47,3 +47,4 @@ humantime = "2.1.0"
 serde = { version = "1", features = ["derive"] }
 toml = "0.5"
 dirs = "4"
+clap_complete = "3"

tokio-console/args.example

@@ -89,6 +89,8 @@ OPTIONS:
  Print version information
 
 SUBCOMMANDS:
+ gen-completion
+ Generate shell completions
  gen-config
  Generate a `console.toml` config file with the default configuration values, overridden
  by any provided command-line arguments

tokio-console/src/config.rs

@@ -1,5 +1,6 @@
 use crate::view::Palette;
-use clap::{ArgGroup, Parser as Clap, Subcommand, ValueHint};
+use clap::{ArgGroup, IntoApp, Parser as Clap, Subcommand, ValueHint};
+use clap_complete::Shell;
 use color_eyre::eyre::WrapErr;
 use serde::{Deserialize, Serialize};
 use std::fmt;
@@ -95,6 +96,18 @@ pub enum OptionalCmd {
  /// $ tokio-console gen-config > console.toml
  ///
  GenConfig,
+
+ /// Generate shell completions
+ ///
+ /// The completion script will be written to stdout.
+ /// The completion script should be saved in the shell's completion directory.
+ /// This depends on which shell is in use.
+ GenCompletion {
+ #[clap(name = "install", long = "install")]
+ install: bool,
+ #[clap(arg_enum)]
+ shell: Shell,
+ },
 }
 
 #[derive(Debug, Clone, Copy, Deserialize)]
@@ -577,6 +590,21 @@ impl ConfigPath {
  }
 }
 
+/// Generete completion scripts for each specified shell.
+pub fn gen_completion(install: bool, shell: Shell) -> color_eyre::Result<()> {
+ let mut app = Config::command();
+ let mut buf: Box<dyn std::io::Write> = if install {
+ color_eyre::eyre::bail!(
+ "Automatically installing completion scripts is not currently supported on {}",
+ shell
+ )
+ } else {
+ Box::new(std::io::stdout())
+ };
+ clap_complete::generate(shell, &mut app, "tokio-console", &mut buf);
+ Ok(())
+}
+
 #[cfg(test)]
 mod tests {
  use std::{

tokio-console/src/main.rs

@@ -27,11 +27,17 @@ mod warnings;
 async fn main() -> color_eyre::Result<()> {
  let mut args = config::Config::parse()?;
 
- if args.subcmd == Some(config::OptionalCmd::GenConfig) {
- // Generate a default config file and exit.
- let toml = args.gen_config_file()?;
- println!("{}", toml);
- return Ok(());
+ match args.subcmd {
+ Some(config::OptionalCmd::GenConfig) => {
+ // Generate a default config file and exit.
+ let toml = args.gen_config_file()?;
+ println!("{}", toml);
+ return Ok(());
+ }
+ Some(config::OptionalCmd::GenCompletion { install, shell }) => {
+ return config::gen_completion(install, shell);
+ }
+ None => {}
  }
 
  let retain_for = args.retain_for();