merge: completions improvements

Cargo.toml

@@ -14,7 +14,7 @@ build = "build.rs"
 
 [dependencies]
 clap = { version = "4.6.6", features = ["derive"] }
-# clap_complete = "4.5.35"
+clap_complete = "4.6.9"
 anyhow = "1.0.104"
 dotenvy = "0.15.7"
 

build.rs

@@ -1,22 +1,55 @@
 use clap::{CommandFactory, ValueEnum};
 use clap_complete::{Shell, generate_to};
-use std::{env, io::Error};
+use std::{env, ffi::OsString, fs, io::Error, path::PathBuf};
 
 include!("src/cli/mod.rs");
 
-fn main() -> Result<(), Error> {
-    let outdir = env::var_os("SHELL_COMPLETIONS_DIR").or_else(|| env::var_os("OUT_DIR"));
+fn shell_name(shell: Shell) -> String {
+    shell
+        .to_possible_value()
+        .map(|v| v.get_name().to_owned())
+        .unwrap_or_default()
+}
 
-    let Some(outdir) = outdir else {
-        return Ok(());
-    };
+fn non_empty(name: &str) -> Option<OsString> {
+    env::var_os(name).filter(|v| !v.is_empty())
+}
+
+fn install_dir(shell: Shell) -> Option<(PathBuf, bool)> {
+    let per_shell = format!("SHELL_COMPLETIONS_DIR_{}", shell_name(shell).to_uppercase());
+
+    if let Some(dir) = non_empty(&per_shell).or_else(|| non_empty("SHELL_COMPLETIONS_DIR")) {
+        return Some((PathBuf::from(dir), true));
+    }
+    non_empty("OUT_DIR").map(|dir| (PathBuf::from(dir), false))
+}
+
+fn main() -> Result<(), Error> {
+    println!("cargo::rerun-if-env-changed=SHELL_COMPLETIONS_DIR");
+    for shell in Shell::value_variants() {
+        println!(
+            "cargo::rerun-if-env-changed=SHELL_COMPLETIONS_DIR_{}",
+            shell_name(*shell).to_uppercase()
+        );
+    }
 
     let mut cmd = ahab::Ahab::command();
 
     for shell in Shell::value_variants() {
-        let path = generate_to(*shell, &mut cmd, env!("CARGO_PKG_NAME"), &outdir)?;
+        let Some((dir, requested)) = install_dir(*shell) else {
+            continue;
+        };
 
-        println!("cargo:warning=completion file is generated: {path:?}");
+        fs::create_dir_all(&dir)?;
+        let path = generate_to(*shell, &mut cmd, env!("CARGO_PKG_NAME"), &dir)?;
+
+        if requested {
+            println!(
+                "cargo::warning=installed {} completion: {}",
+                shell_name(*shell),
+                path.display()
+            );
+        }
     }
 
     Ok(())

src/cli/ahab.rs

@@ -1,5 +1,6 @@
 use super::{Django, DockerCompose, Link, Postgres};
 use clap::{Parser, Subcommand};
+use clap_complete::Shell;
 
 /// A program for interacting with various dockerized applications.
 #[derive(Parser, Debug)]
@@ -34,4 +35,10 @@ pub enum Commands {
         #[command(subcommand)]
         command: Link,
     },
+
+    /// Print a shell completion script on stdout
+    Completions {
+        /// Shell to generate the script for
+        shell: Shell,
+    },
 }

src/main.rs

@@ -50,5 +50,6 @@ fn main() -> Result<()> {
                 null,
             } => scripts::link::check(&paths, porcelain, null),
         },
+        cli::Commands::Completions { shell } => scripts::completions::completions(shell),
     }
 }

src/scripts/completions.rs

@@ -0,0 +1,46 @@
+use std::io::{self, Write};
+
+use anyhow::{Context, Result};
+use clap::CommandFactory;
+use clap_complete::{Shell, generate};
+
+use crate::cli::Ahab;
+
+pub fn completions(shell: Shell) -> Result<()> {
+    let script = script(shell);
+
+    let mut stdout = io::stdout().lock();
+    match stdout.write_all(&script).and_then(|()| stdout.flush()) {
+        Err(e) if e.kind() == io::ErrorKind::BrokenPipe => Ok(()),
+        result => result.context("writing the completion script"),
+    }
+}
+
+fn script(shell: Shell) -> Vec<u8> {
+    let mut cmd = Ahab::command();
+    let name = cmd.get_name().to_string();
+
+    let mut script = Vec::new();
+    generate(shell, &mut cmd, name, &mut script);
+    script
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Shell, script};
+    use clap::ValueEnum;
+
+    #[test]
+    fn every_shell_gets_a_script_covering_the_subcommands() {
+        for shell in Shell::value_variants() {
+            let out = String::from_utf8(script(*shell)).expect("script is utf8");
+
+            for subcommand in ["compose", "django", "postgres", "link", "completions"] {
+                assert!(
+                    out.contains(subcommand),
+                    "{shell:?} script never mentions {subcommand}"
+                );
+            }
+        }
+    }
+}

src/scripts/mod.rs

@@ -1,3 +1,4 @@
+pub mod completions;
 pub mod django;
 pub mod docker;
 pub mod docker_compose;