feat: Add shell completion via clap_complete

Cargo.toml

@@ -49,6 +49,7 @@ xdg = "2.5.2"
 xml-rs = "0.8.20"
 xz2 = "0.1.7"
 zstd = { version = "0.12.4", features = [ "zstdmt" ] }
+clap_complete = "4.5.54"
 
 [dependencies.hyper]
 features = ["client", "http1", "http2", "runtime", "stream"]

src/bin/nix-channel-index.rs

@@ -5,7 +5,8 @@ use std::os::unix::ffi::OsStringExt;
 use std::path::PathBuf;
 use std::process;
 
-use clap::Parser;
+use clap::{CommandFactory, Parser};
+use clap_complete::{generate, Shell};
 use error_chain::ChainedError;
 use futures::{future, StreamExt};
 use nix_index::files::FileNode;
@@ -179,12 +180,26 @@ struct Args {
     /// Show a stack trace in the case of a Nix evaluation error
     #[clap(long)]
     show_trace: bool,
+
+    /// Generate shell completions to stdout.
+    #[clap(long)]
+    completions: Option<Shell>,
 }
 
 #[tokio::main]
 async fn main() {
     let args = Args::parse();
 
+    if let Some(shell) = args.completions {
+        generate(
+            shell,
+            &mut Args::command(),
+            "nix-channel-index",
+            &mut io::stdout(),
+        );
+        return;
+    }
+
     if let Err(e) = update_index(&args).await {
         eprintln!("error: {}", e);
 

src/bin/nix-index.rs

@@ -5,7 +5,8 @@ use std::io::{self, Write};
 use std::path::PathBuf;
 use std::process;
 
-use clap::Parser;
+use clap::{CommandFactory, Parser};
+use clap_complete::{generate, Shell};
 use error_chain::ChainedError;
 use futures::future::Either;
 use futures::{future, StreamExt};
@@ -153,12 +154,21 @@ struct Args {
     /// Note: does not check if the cached data is up to date! Use only for development.
     #[clap(long)]
     path_cache: bool,
+
+    /// Generate shell completions to stdout.
+    #[clap(long)]
+    completions: Option<Shell>,
 }
 
 #[tokio::main]
 async fn main() {
     let args = Args::parse();
 
+    if let Some(shell) = args.completions {
+        generate(shell, &mut Args::command(), "nix-index", &mut io::stdout());
+        return;
+    }
+
     if let Err(e) = update_index(&args).await {
         eprintln!("error: {}", e);
 

src/bin/nix-locate.rs

@@ -1,13 +1,17 @@
 //! Tool for searching for files in nixpkgs packages
 use std::collections::HashSet;
 use std::ffi::OsStr;
+use std::io;
 use std::path::PathBuf;
 use std::process;
 use std::result;
 use std::str;
 use std::str::FromStr;
 
+use clap::CommandFactory;
 use clap::{value_parser, Parser};
+use clap_complete::generate;
+use clap_complete::Shell;
 use error_chain::error_chain;
 use nix_index::database;
 use nix_index::files::{self, FileTreeEntry, FileType};
@@ -153,7 +157,10 @@ fn locate(args: &Args) -> Result<()> {
 ///
 /// Handles parsing the values of more complex arguments.
 fn process_args(matches: Opts) -> result::Result<Args, clap::Error> {
-    let pattern_arg = matches.pattern;
+    let pattern_arg = matches.pattern.ok_or(Opts::command().error(
+        clap::error::ErrorKind::MissingRequiredArgument,
+        "The argument <PATTERN> is missing",
+    ))?;
     let package_arg = matches.package;
 
     let start_anchor = if matches.at_root { "^" } else { "" };
@@ -237,7 +244,7 @@ fn cache_dir() -> &'static OsStr {
 struct Opts {
     /// Pattern for which to search
     // #[clap(name = "PATTERN")]
-    pattern: String,
+    pattern: Option<String>,
 
     /// Directory where the index is stored
     #[clap(short, long = "db", default_value_os = cache_dir(), env = "NIX_INDEX_DATABASE")]
@@ -293,6 +300,10 @@ struct Opts {
     /// store path are omitted. This is useful for scripts that use the output of nix-locate.
     #[clap(long)]
     minimal: bool,
+
+    /// Generate shell completions to stdout.
+    #[clap(long)]
+    completions: Option<Shell>,
 }
 
 #[derive(clap::ValueEnum, Clone, Copy, Debug)]
@@ -318,6 +329,11 @@ impl FromStr for Color {
 fn main() {
     let args = Opts::parse();
 
+    if let Some(shell) = args.completions {
+        generate(shell, &mut Opts::command(), "nix-locate", &mut io::stdout());
+        return;
+    }
+
     let args = process_args(args).unwrap_or_else(|e| e.exit());
 
     if let Err(e) = locate(&args) {