improve error

src/lib.rs

@@ -55,18 +55,29 @@ mod listener;
 pub use listener::ShortcutListener;
 
 /// Error emitted when an input device can't be opened
-#[derive(Debug, Clone)]
+#[derive(Debug)]
+#[non_exhaustive]
 pub struct DeviceOpenError {
     pub device: PathBuf,
+    pub error: std::io::Error,
 }
 
 impl Display for DeviceOpenError {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        write!(f, "Failed to open device {:?}", self.device)
+        write!(
+            f,
+            "Failed to open device {}: {:#}",
+            self.device.display(),
+            self.error
+        )
     }
 }
 
-impl std::error::Error for DeviceOpenError {}
+impl std::error::Error for DeviceOpenError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        Some(&self.error)
+    }
+}
 
 /// Modifier key for shortcuts
 #[derive(Clone, Copy, Debug, Hash, Eq, PartialEq, Display, FromStr)]

src/listener.rs

@@ -52,8 +52,9 @@ impl ShortcutListener {
             .iter()
             .map(|path| {
                 let path = path.as_ref();
-                let res = Device::open(path).map_err(|_| DeviceOpenError {
+                let res = Device::open(path).map_err(|error| DeviceOpenError {
                     device: path.into(),
+                    error,
                 });
                 debug!(device = ?path, success = res.is_ok(), "opening input device");
                 res