Attach underlying IO error to light node Kind::Io error (#413)

light-node/src/error.rs

@@ -1,8 +1,9 @@
 //! Error types
 
-use std::io;
 use std::net;
 
+use anomaly::{BoxError, Context};
+
 /// Error type
 pub type Error = anomaly::Error<Kind>;
 
@@ -18,12 +19,14 @@ pub enum Kind {
     Config,
 
     /// Input/output error
-    #[error("i/o error: {0}")]
-    Io(String),
+    #[error("i/o error")]
+    Io,
 }
 
-impl From<io::Error> for Kind {
-    fn from(err: io::Error) -> Self {
-        Self::Io(format!("{}", err))
+impl Kind {
+    /// Add additional context (i.e. include a source error and capture a backtrace).
+    /// You can convert the resulting `Context` into an `Error` by calling `.into()`.
+    pub fn context(self, source: impl Into<BoxError>) -> Context<Self> {
+        Context::new(self, Some(source.into()))
     }
 }

light-node/src/rpc.rs

@@ -25,7 +25,7 @@ where
             AccessControlAllowOrigin::Any,
         ]))
         .start_http(&addr.parse().map_err(error::Kind::from)?)
-        .map_err(error::Kind::from)?;
+        .map_err(|e| error::Kind::Io.context(e))?;
 
     srv.wait();