Add nushell completion support (#2009)

* Add nushell completion support

Adds `clap_complete_nushell` crate and implements it into the `niri
completions` command.

* Add nushell to flake.nix autocompletions

* Convert to `TryFrom`

* Fix linting errors

* Move types down

---------

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

2 files changed, 48 insertions, 3 deletions

diff --git a/src/cli.rs b/src/cli.rs
index cb3cc0ab..933712c2 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -56,7 +56,7 @@ pub enum Sub {
     /// Cause a panic to check if the backtraces are good.
     Panic,
     /// Generate shell completions.
-    Completions { shell: Shell },
+    Completions { shell: CompletionShell },
 }
 
 #[derive(Subcommand)]
@@ -108,3 +108,28 @@ pub enum Msg {
     /// Print the overview state.
     OverviewState,
 }
+
+#[derive(Clone, Debug, clap::ValueEnum)]
+pub enum CompletionShell {
+    Bash,
+    Elvish,
+    Fish,
+    PowerShell,
+    Zsh,
+    Nushell,
+}
+
+impl TryFrom<CompletionShell> for Shell {
+    type Error = &'static str;
+
+    fn try_from(shell: CompletionShell) -> Result<Self, Self::Error> {
+        match shell {
+            CompletionShell::Bash => Ok(Shell::Bash),
+            CompletionShell::Elvish => Ok(Shell::Elvish),
+            CompletionShell::Fish => Ok(Shell::Fish),
+            CompletionShell::PowerShell => Ok(Shell::PowerShell),
+            CompletionShell::Zsh => Ok(Shell::Zsh),
+            CompletionShell::Nushell => Err("Nushell should be handled separately"),
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 0eeb57bf..73d60bb4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,8 +10,10 @@ use std::process::Command;
 use std::{env, mem};
 
 use clap::{CommandFactory, Parser};
+use clap_complete::Shell;
+use clap_complete_nushell::Nushell;
 use directories::ProjectDirs;
-use niri::cli::{Cli, Sub};
+use niri::cli::{Cli, CompletionShell, Sub};
 #[cfg(feature = "dbus")]
 use niri::dbus;
 use niri::ipc::client::handle_msg;
@@ -108,7 +110,25 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             }
             Sub::Panic => cause_panic(),
             Sub::Completions { shell } => {
-                clap_complete::generate(shell, &mut Cli::command(), "niri", &mut io::stdout());
+                match shell {
+                    CompletionShell::Nushell => {
+                        clap_complete::generate(
+                            Nushell,
+                            &mut Cli::command(),
+                            "niri",
+                            &mut io::stdout(),
+                        );
+                    }
+                    other => {
+                        let generator = Shell::try_from(other).unwrap();
+                        clap_complete::generate(
+                            generator,
+                            &mut Cli::command(),
+                            "niri",
+                            &mut io::stdout(),
+                        );
+                    }
+                }
                 return Ok(());
             }
         }