optimize the config parsing

Author: fluiderson

src/tools/jsondocck/src/config.rs

@@ -1,3 +1,6 @@
+use std::cell::LazyCell;
+use std::env::Args;
+
 use getopts::Options;
 
 #[derive(Debug)]
@@ -8,30 +11,32 @@ pub struct Config {
     pub template: String,
 }
 
-/// Create [`Config`] from a vector of command-line arguments.
-pub fn parse_config(args: Vec<String>) -> Config {
+/// Create [`Config`] from an iterator of command-line arguments.
+pub fn parse_config(mut args: Args) -> Option<Config> {
     let mut opts = Options::new();
     opts.reqopt("", "doc-dir", "Path to the documentation output directory.", "PATH")
         .reqopt("", "template", "Path to the input template file.", "PATH")
         .optflag("h", "help", "Show this message.");
 
-    let (argv0, args_) = args.split_first().unwrap();
-    if args.len() == 1 {
-        let message = format!("Usage: {} <doc-dir> <template>", argv0);
-        println!("{}", opts.usage(&message));
-        std::process::exit(1);
+    let argv0 = args.next().unwrap();
+    let usage = &*LazyCell::new(|| opts.usage(&format!("Usage: {argv0} <doc-dir> <template>")));
+
+    if args.len() == 0 {
+        print!("{usage}");
+
+        return None;
     }
 
-    let matches = opts.parse(args_).unwrap();
+    let matches = opts.parse(args).unwrap();
 
     if matches.opt_present("h") || matches.opt_present("help") {
-        let message = format!("Usage: {} <doc-dir> <template>", argv0);
-        println!("{}", opts.usage(&message));
-        std::process::exit(1);
+        print!("{usage}");
+
+        return None;
     }
 
-    Config {
+    Some(Config {
         doc_dir: matches.opt_str("doc-dir").unwrap(),
         template: matches.opt_str("template").unwrap(),
-    }
+    })
 }

src/tools/jsondocck/src/main.rs

@@ -15,7 +15,9 @@ use directive::{Directive, DirectiveKind};
 use error::CkError;
 
 fn main() -> ExitCode {
-    let config = parse_config(env::args().collect());
+    let Some(config) = parse_config(env::args()) else {
+        return ExitCode::FAILURE;
+    };
 
     let mut failed = Vec::new();
     let mut cache = Cache::new(&config);