main: clear error messages and exit codes instead of panics

Missing/invalid config, unwritable config target, failed Wayland connect
and bad arguments now print one line to stderr and exit 1 rather than
panicking with "uh" or a serde backtrace.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/draw.rs

@@ -82,7 +82,7 @@ pub struct Font<'a> {
 }
 
 impl<'a> Font<'a> {
-    pub fn new(font: FontRef<'a>, size: f32) -> Font {
+    pub fn new(font: FontRef<'a>, size: f32) -> Font<'a> {
         Font {
             glyphs: HashMap::new(),
             font,

src/main.rs

@@ -56,10 +56,14 @@ OPTIONS:
     );
 }
 
+fn die(msg: String) -> ! {
+    eprintln!("wldash: {}", msg);
+    std::process::exit(1);
+}
+
 fn ensure_dir_exists(path: &str) {
-    match fs::create_dir_all(path) {
-        Ok(_) => (),
-        Err(err) => panic!("error creating directory: {}", err),
+    if let Err(err) = fs::create_dir_all(path) {
+        die(format!("error creating directory {}: {}", path, err));
     }
 }
 
@@ -95,7 +99,7 @@ fn main() {
         match args.next() {
             Some(ref s) if s == "--config" => match args.next() {
                 Some(ref s) => config_file = s.clone(),
-                None => panic!("missing argument to --config"),
+                None => die("missing argument to --config".to_string()),
             },
             Some(ref s) if s == "--write-default-config" => {
                 let config = match args.next() {
@@ -103,17 +107,23 @@ fn main() {
                     Some(ref s) if s == "v2" => Config::generate_v2(false),
                     Some(ref s) if s == "toplevel" => Config::generate_v2(true),
                     None => Config::generate_v2(false),
-                    Some(s) => panic!("unknown argument: {}", s),
+                    Some(s) => die(format!("unknown argument to --write-default-config: {}", s)),
                 };
-                match File::create(config_file) {
-                    Ok(f) => serde_yaml::to_writer(f, &config).unwrap(),
-                    Err(_) => panic!("uh"),
+                match File::create(&config_file) {
+                    Ok(f) => {
+                        if let Err(e) = serde_yaml::to_writer(f, &config) {
+                            die(format!("could not serialize config: {}", e));
+                        }
+                    }
+                    Err(e) => die(format!("could not write {}: {}", config_file, e)),
                 }
                 std::process::exit(0);
             }
             Some(ref s) if s == "--desktop-refresh" => {
                 let v = load_desktop_files();
-                write_desktop_cache(&v).unwrap();
+                if let Err(e) = write_desktop_cache(&v) {
+                    die(format!("could not write desktop cache: {}", e));
+                }
                 std::process::exit(0);
             }
             Some(ref s) if s == "--help" => {
@@ -128,7 +138,10 @@ fn main() {
         }
     }
 
-    let conn = Connection::connect_to_env().unwrap();
+    let conn = match Connection::connect_to_env() {
+        Ok(c) => c,
+        Err(e) => die(format!("could not connect to the Wayland display: {}", e)),
+    };
 
     let event_queue = conn.new_event_queue();
     let qhandle: QueueHandle<State> = event_queue.handle();
@@ -204,9 +217,15 @@ fn main() {
 
     let mut fm = FontMap::new();
 
-    let config: Config = match File::open(config_file) {
-        Ok(f) => serde_yaml::from_reader(f).unwrap(),
-        Err(_) => panic!("configuration file missing: try 'wldash --write-default-config'"),
+    let config: Config = match File::open(&config_file) {
+        Ok(f) => match serde_yaml::from_reader(f) {
+            Ok(c) => c,
+            Err(e) => die(format!("invalid configuration {}: {}", config_file, e)),
+        },
+        Err(e) => die(format!(
+            "could not open configuration {}: {} (try 'wldash --write-default-config')",
+            config_file, e
+        )),
     };
 
     if let Some(true) = config.server {
@@ -292,7 +311,7 @@ fn main() {
         }
 
         let mut force = false;
-        if state.bufmgr.buffers.len() == 0 {
+        if state.bufmgr.buffers.is_empty() {
             state.add_buffer(&qhandle);
             force = true;
         }
@@ -316,7 +335,7 @@ fn main() {
             }
         };
 
-        if buf.last_damage.len() == 0 {
+        if buf.last_damage.is_empty() {
             for _ in 0..state.widgets.len() {
                 buf.last_damage.push(Geometry::new());
             }