feat: anyhow error handling

Cargo.lock

@@ -117,6 +117,7 @@ checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 name = "chkr"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "crossterm",
  "insta",
  "ratatui",

Cargo.toml

@@ -6,6 +6,7 @@ edition = "2024"
 [dependencies]
 crossterm = "0.29"
 ratatui = { version = "0.30", features = ["crossterm"] }
+anyhow = "1.0"
 
 [dev-dependencies]
 insta = "1.33"

src/event_source.rs

@@ -1,5 +1,5 @@
+use anyhow::Result;
 use crossterm::event::{self, Event};
-use std::error::Error;
 use std::time::Duration;
 
 /// An abstraction around event sourcing so we can inject events in tests.
@@ -7,21 +7,21 @@ pub trait EventSource {
     /// Polls for an event for up to `timeout`, returning `Ok(true)` if an event is
     /// available, `Ok(false)` if the timeout elapsed without an event, or an `Err`
     /// if polling failed.
-    fn poll(&mut self, timeout: Duration) -> Result<bool, Box<dyn Error>>;
+    fn poll(&mut self, timeout: Duration) -> Result<bool>;
 
     /// Reads the next available event, or returns an `Err` if reading fails.
-    fn read(&mut self) -> Result<Event, Box<dyn Error>>;
+    fn read(&mut self) -> Result<Event>;
 }
 
 /// Production implementation that delegates to `crossterm::event`.
 pub struct CrosstermEventSource;
 
 impl EventSource for CrosstermEventSource {
-    fn poll(&mut self, timeout: Duration) -> Result<bool, Box<dyn Error>> {
+    fn poll(&mut self, timeout: Duration) -> Result<bool> {
         Ok(event::poll(timeout).map_err(Box::new)?)
     }
 
-    fn read(&mut self) -> Result<Event, Box<dyn Error>> {
+    fn read(&mut self) -> Result<Event> {
         Ok(event::read().map_err(Box::new)?)
     }
 }

src/main.rs

@@ -1,8 +1,10 @@
+/// A simple terminal checklist application.
 mod event_source;
 mod terminal_guard;
 /// UI components (todo list)
 mod todo_list;
 
+use anyhow::{Context as _, Result, anyhow, bail};
 use core::time::Duration;
 use crossterm::event::{self, EnableMouseCapture, Event, KeyCode};
 use crossterm::execute;
@@ -15,10 +17,11 @@ use std::io::{self, Read as _};
 use terminal_guard::TerminalModeGuard;
 use todo_list::TodoList;
 
-#[allow(clippy::wildcard_enum_match_arm)]
+fn main() -> Result<()> {
-fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut input = String::new();
-    io::stdin().read_to_string(&mut input)?;
+    io::stdin()
+        .read_to_string(&mut input)
+        .context("reading stdin")?;
 
     if input.trim().is_empty() {
         eprintln!("Provide text via stdin (pipe or heredoc). Example: \n  cat file.txt | chkr");
@@ -31,31 +34,34 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .collect();
     let mut todo = TodoList::with_lines(lines);
 
-    enable_raw_mode()?;
+    enable_raw_mode().context("enable raw mode")?;
     let mut stdout = std::io::stdout();
-    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
+    execute!(stdout, EnterAlternateScreen, EnableMouseCapture).context("enter alternate screen")?;
 
     let mode_guard = TerminalModeGuard;
 
     let backend = CrosstermBackend::new(stdout);
-    let mut terminal = Terminal::new(backend)?;
+    let mut terminal = Terminal::new(backend).context("create terminal")?;
 
-    run_app(&mut terminal, &mut CrosstermEventSource, &mut todo)?;
+    run_app(&mut terminal, &mut CrosstermEventSource, &mut todo)
+        .map_err(|e| anyhow!("running app: {e}"))?;
 
     drop(mode_guard);
-    terminal.show_cursor()?;
+    terminal.show_cursor().context("show cursor")?;
 
     Ok(())
 }
 
 /// Run the app loop using an abstract `EventSource` so tests can inject events.
+/// # Errors
+/// If terminal drawing or event sourcing fails.
 pub fn run_app<B: Backend, E: EventSource>(
     terminal: &mut Terminal<B>,
     event_source: &mut E,
     todo: &mut TodoList,
-) -> Result<(), Box<dyn std::error::Error>>
+) -> Result<()>
 where
-    <B as Backend>::Error: 'static,
+    <B as Backend>::Error: 'static + Sync + Send,
 {
     loop {
         terminal.draw(|f| {
@@ -63,6 +69,7 @@ where
         })?;
 
         if event_source.poll(Duration::from_millis(100))? {
+            #[allow(clippy::wildcard_enum_match_arm)]
             match event_source.read()? {
                 Event::Key(key) => match key.code {
                     KeyCode::Char('q') => break,
@@ -79,7 +86,7 @@ where
                     KeyCode::Char(' ') => {
                         if let Some(i) = todo.state.selected() {
                             let Some(marked_cell) = todo.marked.get_mut(i) else {
-                                return Err("Index out of bounds".into());
+                                bail!("Index out of bounds");
                             };
                             if !*marked_cell {
                                 let next = todo.lines.len().min(i + 1);
@@ -140,11 +147,11 @@ mod tests {
     }
 
     impl crate::event_source::EventSource for MockEventSource {
-        fn poll(&mut self, _timeout: Duration) -> Result<bool, Box<dyn std::error::Error>> {
+        fn poll(&mut self, _timeout: Duration) -> Result<bool> {
             Ok(!self.events.is_empty())
         }
 
-        fn read(&mut self) -> Result<Event, Box<dyn std::error::Error>> {
+        fn read(&mut self) -> Result<Event> {
             Ok(self.events.pop_front().expect("no events left"))
         }
     }