feat(cli): add shell completion support

xee/Cargo.toml

@@ -17,6 +17,7 @@ xee-xslt-compiler = { path = "../xee-xslt-compiler", version = "0.1.6" }
 xee-interpreter = { path = "../xee-interpreter", version = "0.2.0" }
 xot = { workspace = true }
 clap = { workspace = true, features = ["derive", "cargo"] }
+clap_complete = "4.6.0"
 ariadne = "0.5.1"
 anyhow.workspace = true
 regex = { workspace = true }

xee/src/completion.rs

@@ -0,0 +1,48 @@
+use std::io;
+
+use clap::{CommandFactory, Parser};
+use clap_complete::Shell;
+
+use crate::Cli;
+
+/// Generate shell completion scripts.
+///
+/// The completion script is written to stdout.
+#[derive(Debug, Parser)]
+pub(crate) struct Completion {
+    /// The shell to generate completions for.
+    pub(crate) shell: Shell,
+}
+
+impl Completion {
+    pub(crate) fn run(&self) -> anyhow::Result<()> {
+        let mut cmd = Cli::command();
+        clap_complete::generate(self.shell, &mut cmd, "xee", &mut io::stdout());
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use clap::ValueEnum;
+
+    use super::*;
+
+    #[test]
+    fn verify_cli_for_completion() {
+        Cli::command().debug_assert();
+    }
+
+    #[test]
+    fn generate_completions_for_all_shells() {
+        for shell in Shell::value_variants() {
+            let mut cmd = Cli::command();
+            let mut buf = Vec::new();
+            clap_complete::generate(*shell, &mut cmd, "xee", &mut buf);
+            assert!(
+                !buf.is_empty(),
+                "completion output for {shell} should not be empty"
+            );
+        }
+    }
+}

xee/src/main.rs

@@ -1,4 +1,5 @@
 mod common;
+mod completion;
 mod error;
 mod format;
 mod indent;
@@ -32,11 +33,16 @@ enum Commands {
     Repl(repl::Repl),
     /// Transform an XML document using an XSLT stylesheet.
     Xslt(xslt::Xslt),
+    /// Generate shell completion scripts.
+    Completion(completion::Completion),
 }
 
 fn main() -> anyhow::Result<()> {
     let cli = Cli::parse();
     match cli.command {
+        Commands::Completion(completion) => {
+            completion.run()?;
+        }
         Commands::Indent(indent) => {
             indent.run()?;
         }