Surface bitcoind rpc error code

Users of the RpcClient had no way to access the error code
returned by bitcoind's rpc.  We embed a new RpcError struct
as the inner error for the returned io::Error. Users can access
both the code and the message using this inner struct.

diff --git a/lightning-block-sync/src/rpc.rs b/lightning-block-sync/src/rpc.rs
index f04769560246f8537e1e022efa22c8b7a815eab4..6b4397a6b0fbe87d19a130fa18002a27042c9864 100644 (file)
--- a/lightning-block-sync/src/rpc.rs
+++ b/lightning-block-sync/src/rpc.rs
@@ -13,8 +13,27 @@ use serde_json;
 
 use std::convert::TryFrom;
 use std::convert::TryInto;
+use std::error::Error;
+use std::fmt;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
+/// An error returned by the RPC server.
+#[derive(Debug)]
+pub struct RpcError {
+       /// The error code.
+       pub code: i64,
+       /// The error message.
+       pub message: String,
+}
+
+impl fmt::Display for RpcError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "RPC error {}: {}", self.code, self.message)
+    }
+}
+
+impl Error for RpcError {}
+
 /// A simple RPC client for calling methods using HTTP `POST`.
 pub struct RpcClient {
        basic_auth: String,
@@ -69,8 +88,11 @@ impl RpcClient {
                let error = &response["error"];
                if !error.is_null() {
                        // TODO: Examine error code for a more precise std::io::ErrorKind.
-                       let message = error["message"].as_str().unwrap_or("unknown error");
-                       return Err(std::io::Error::new(std::io::ErrorKind::Other, message));
+                       let rpc_error = RpcError { 
+                               code: error["code"].as_i64().unwrap_or(-1), 
+                               message: error["message"].as_str().unwrap_or("unknown error").to_string() 
+                       };
+                       return Err(std::io::Error::new(std::io::ErrorKind::Other, rpc_error));
                }
 
                let result = &mut response["result"];
@@ -163,7 +185,9 @@ mod tests {
                match client.call_method::<u64>("getblock", &[invalid_block_hash]).await {
                        Err(e) => {
                                assert_eq!(e.kind(), std::io::ErrorKind::Other);
-                               assert_eq!(e.get_ref().unwrap().to_string(), "invalid parameter");
+                               let rpc_error: Box<RpcError> = e.into_inner().unwrap().downcast().unwrap();
+                               assert_eq!(rpc_error.code, -8);
+                               assert_eq!(rpc_error.message, "invalid parameter");
                        },
                        Ok(_) => panic!("Expected error"),
                }