feat: add shell completions

Cargo.toml

@@ -33,6 +33,8 @@ nix_rs = { version = "0.5.0", features = ["clap"] }
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
 tracing = "0.1.37"
 nix_health = "0.4.1"
+clap_complete = "4.4.0"
+async-trait = "0.1.73"
 
 [dev-dependencies]
 regex = "1.9"

flake.nix

@@ -78,7 +78,15 @@
         };
 
         # Flake outputs
-        packages.default = self'.packages.nixci;
+        packages.default = self'.packages.nixci.overrideAttrs (oa: {
+          nativeBuildInputs = (oa.nativeBuildInputs or [ ]) ++ [ pkgs.installShellFiles pkgs.nix ];
+          postInstall = ''
+            installShellCompletion --cmd nixci \
+              --bash <($out/bin/nixci completion bash) \
+              --zsh <($out/bin/nixci completion zsh) \
+              --fish <($out/bin/nixci completion fish)
+          '';
+        });
         overlayAttrs.nixci = self'.packages.default;
 
         devShells.default = pkgs.mkShell {

src/cli.rs

@@ -1,14 +1,5 @@
 use std::str::FromStr;
 
-use anyhow::Result;
-use clap::{Parser, Subcommand};
-use colored::Colorize;
-use nix_rs::{
-    command::NixCmd,
-    config::NixConfig,
-    flake::{system::System, url::FlakeUrl},
-};
-
 use crate::{
     config,
     github::pull_request::{PullRequest, PullRequestRef},
@@ -17,6 +8,14 @@ use crate::{
         system_list::{SystemsList, SystemsListFlakeRef},
     },
 };
+use anyhow::Result;
+use clap::{Parser, Subcommand};
+use colored::Colorize;
+use nix_rs::{
+    command::NixCmd,
+    config::NixConfig,
+    flake::{system::System, url::FlakeUrl},
+};
 
 /// A reference to some flake living somewhere
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -108,15 +107,17 @@ pub enum Command {
         #[arg(long, value_parser, value_delimiter = ',')]
         systems: Vec<System>,
     },
+
+    /// Generates shell completion scripts
+    Completion {
+        #[arg(value_enum)]
+        shell: clap_complete::Shell,
+    },
 }
 
 impl Command {
     /// Get the nixci [config::Config] associated with this subcommand
-    pub async fn get_config(&self, cmd: &NixCmd) -> anyhow::Result<config::Config> {
-        let flake_ref = match self {
-            Command::Build(build_cfg) => &build_cfg.flake_ref,
-            Command::DumpGithubActionsMatrix { flake_ref, .. } => flake_ref,
-        };
+    pub async fn get_config(cmd: &NixCmd, flake_ref: &FlakeRef) -> anyhow::Result<config::Config> {
         let url = flake_ref.to_flake_url().await?;
         tracing::info!("{}", format!("🍏 {}", url.0).bold());
         let cfg = config::Config::from_flake_url(cmd, &url).await?;

src/lib.rs

@@ -4,9 +4,12 @@ pub mod github;
 pub mod logging;
 pub mod nix;
 
+use anyhow::{Context, Ok};
+use clap::CommandFactory;
+use clap_complete::generate;
 use std::collections::HashSet;
+use std::io;
 
-use anyhow::Context;
 use cli::{BuildConfig, CliArgs};
 use colored::Colorize;
 use nix::{
@@ -21,9 +24,10 @@ use tracing::instrument;
 #[instrument(name = "nixci", skip(args))]
 pub async fn nixci(args: CliArgs) -> anyhow::Result<Vec<StorePath>> {
     tracing::debug!("Args: {args:?}");
-    let cfg = args.command.get_config(&args.nixcmd).await?;
+
     match args.command {
         cli::Command::Build(build_cfg) => {
+            let cfg = cli::Command::get_config(&args.nixcmd, &build_cfg.flake_ref).await?;
             let nix_info = NixInfo::from_nix(&args.nixcmd)
                 .await
                 .with_context(|| "Unable to gather nix info")?;
@@ -39,11 +43,20 @@ pub async fn nixci(args: CliArgs) -> anyhow::Result<Vec<StorePath>> {
             )
             .await
         }
-        cli::Command::DumpGithubActionsMatrix { systems, .. } => {
+        cli::Command::DumpGithubActionsMatrix {
+            systems, flake_ref, ..
+        } => {
+            let cfg = cli::Command::get_config(&args.nixcmd, &flake_ref).await?;
             let matrix = github::matrix::GitHubMatrix::from(systems, &cfg.subflakes);
             println!("{}", serde_json::to_string(&matrix)?);
             Ok(vec![])
         }
+        cli::Command::Completion { shell, .. } => {
+            let mut cli = CliArgs::command();
+            let name = cli.get_name().to_string();
+            generate(shell, &mut cli, name, &mut io::stdout());
+            Ok(vec![])
+        }
     }
 }