refactor: Clean up build/main separation of the infra CLI

crates/infra/cli/build.rs

@@ -1,32 +1,31 @@
 use anyhow::Result;
 use clap::CommandFactory;
-use clap_complete::generate;
-use clap_complete::shells::Zsh;
+use clap_complete::{Generator, Shell};
 use infra_utils::cargo::CargoWorkspace;
 use infra_utils::codegen::Codegen;
 
-// Need this hack to import the source crate as a module:
-#[path = "./src/main.rs"]
-mod crate_main;
-pub use crate_main::*;
+// We use the `clap_complete` pattern of sharing the same crate entry point between
+// the main lib/bin target and the build script to generate the completions at compile-time.
+// See <https://docs.rs/clap_complete/latest/clap_complete/generator/fn.generate_to.html>.
+include!("src/lib.rs");
 
 fn main() -> Result<()> {
-    generate_zsh_completions()?;
-
-    Ok(())
+    generate_completions(Shell::Zsh)
 }
 
 /// Generate auto-completions for the shell.
-fn generate_zsh_completions() -> Result<()> {
+fn generate_completions(shell: Shell) -> Result<()> {
     let mut buffer = vec![];
-    let mut command = <crate_main::commands::CLI as CommandFactory>::command();
 
-    generate(Zsh, &mut command, "infra", &mut buffer);
+    let mut command = CLI::command();
+    command.build();
+
+    shell.generate(&command, &mut buffer);
 
     let crate_dir = CargoWorkspace::locate_source_crate("infra_cli")?;
 
     Codegen::write_only()?.write_file(
-        crate_dir.join("generated/infra.zsh-completions"),
+        crate_dir.join(format!("generated/infra.{shell}-completions")),
         String::from_utf8(buffer)?,
     )
 }

crates/infra/cli/src/lib.rs

@@ -0,0 +1,12 @@
+pub mod commands;
+pub mod toolchains;
+pub mod utils;
+
+pub use crate::commands::CLI;
+pub use crate::utils::Terminal;
+
+#[test]
+fn verify_clap_cli() {
+    // Catches problems earlier in the development cycle:
+    <CLI as clap::CommandFactory>::command().debug_assert();
+}

crates/infra/cli/src/main.rs

@@ -1,13 +1,8 @@
-pub mod commands;
-pub mod toolchains;
-pub mod utils;
+#![allow(unused_crate_dependencies)] // dependencies are almost exclusively used by the lib target
 
 use clap::Parser;
+use infra_cli::{Terminal, CLI};
 
-use crate::commands::CLI;
-use crate::utils::Terminal;
-
-#[allow(dead_code)] // as it is referenced from 'build.rs' of the same crate.
 fn main() {
     let std_hook = std::panic::take_hook();
 
@@ -23,9 +18,3 @@ fn main() {
     CLI::parse().execute().unwrap();
     Terminal::success();
 }
-
-#[test]
-fn verify_clap_cli() {
-    // Catches problems earlier in the development cycle:
-    <CLI as clap::CommandFactory>::command().debug_assert();
-}