Add shell completion generation

crates/geth-cli/src/lib.rs

@@ -1,16 +1,18 @@
 use anyhow::{Context, Result, bail};
 use base64::Engine;
-use clap::{Args, Parser, Subcommand, ValueEnum};
+use clap::{Args, CommandFactory, Parser, Subcommand, ValueEnum};
+use clap_complete::{Shell, generate};
 use geth_config::GethPaths;
 use geth_control::{ControlRequest, ControlResponse};
 use geth_node::service::{ServiceInstallOptions, ServiceManager, ServiceReport};
-use std::io::Read;
+use std::io::{Read, stdout};
 use std::path::PathBuf;
 
 const TOP_LEVEL_AFTER_HELP: &str = r#"Common starts:
   geth guide init
   geth guide owner-setup
   geth guide overlay
+  geth guide completions
   geth init
   geth init --admin-key ~/.ssh/id_ed25519_sk.pub --signing-key ~/.ssh/id_ed25519_sk --node-name laptop
   geth daemon run
@@ -73,6 +75,7 @@ Topics:
   keys          Meaning of --admin-key and --signing-key.
   overlay       Optional Iroh overlay network planning.
   service       Install and manage geth as a user service.
+  completions   Shell completion installation examples.
   smoke-test    Minimal commands to verify a node and daemon."#;
 
 const GUIDE_INIT: &str = r#"geth init has two modes.
@@ -178,6 +181,34 @@ Preview definitions without installing:
   geth daemon service print
 "#;
 
+const GUIDE_COMPLETIONS: &str = r#"Shell completions:
+
+geth can print completions for bash, zsh, fish, PowerShell, and elvish. The
+generated scripts are produced from the same Clap command tree as `geth --help`,
+so subcommands and flags stay in sync with the executable.
+
+Bash:
+  mkdir -p ~/.local/share/bash-completion/completions
+  geth completions bash > ~/.local/share/bash-completion/completions/geth
+
+Zsh:
+  mkdir -p ~/.zfunc
+  geth completions zsh > ~/.zfunc/_geth
+  # Ensure ~/.zfunc is in fpath, then run: compinit
+
+Fish:
+  mkdir -p ~/.config/fish/completions
+  geth completions fish > ~/.config/fish/completions/geth.fish
+
+PowerShell:
+  geth completions powershell > geth.ps1
+  # Source geth.ps1 from your PowerShell profile.
+
+Elvish:
+  mkdir -p ~/.elvish/lib
+  geth completions elvish > ~/.elvish/lib/geth.elv
+"#;
+
 const GUIDE_OVERLAY: &str = r#"Optional overlay network:
 
 geth has an experimental overlay-network design inspired by iroh-lan. The
@@ -256,6 +287,10 @@ pub enum Command {
         #[arg(value_enum)]
         topic: Option<GuideTopic>,
     },
+    Completions {
+        #[arg(value_enum)]
+        shell: Shell,
+    },
     #[command(long_about = INIT_LONG_ABOUT, after_long_help = INIT_AFTER_HELP)]
     Init {
         #[arg(
@@ -366,6 +401,7 @@ pub enum GuideTopic {
     Keys,
     Overlay,
     Service,
+    Completions,
     SmokeTest,
 }
 
@@ -1063,6 +1099,10 @@ pub struct EmptyArgs {}
 
 pub async fn run() -> Result<()> {
     let cli = Cli::parse();
+    if let Command::Completions { shell } = &cli.command {
+        print_completions(*shell);
+        return Ok(());
+    }
     let paths = GethPaths::resolve().context("resolve geth paths")?;
     match cli.command {
         Command::Guide { topic } => {
@@ -1169,6 +1209,7 @@ fn print_guide(topic: Option<GuideTopic>, json: bool) -> Result<()> {
         Some(GuideTopic::Keys) => ("keys", GUIDE_KEYS),
         Some(GuideTopic::Overlay) => ("overlay", GUIDE_OVERLAY),
         Some(GuideTopic::Service) => ("service", GUIDE_SERVICE),
+        Some(GuideTopic::Completions) => ("completions", GUIDE_COMPLETIONS),
         Some(GuideTopic::SmokeTest) => ("smoke-test", GUIDE_SMOKE_TEST),
     };
     if json {
@@ -1185,8 +1226,14 @@ fn print_guide(topic: Option<GuideTopic>, json: bool) -> Result<()> {
     Ok(())
 }
 
+fn print_completions(shell: Shell) {
+    let mut command = Cli::command();
+    generate(shell, &mut command, "geth", &mut stdout());
+}
+
 fn request_for_command(command: Command) -> Result<ControlRequest> {
     Ok(match command {
+        Command::Completions { .. } => bail!("completion generation does not use the daemon"),
         Command::Status => ControlRequest::Status,
         Command::Sync {
             command: SyncCommand::Status,