rfq: refine error code handling

Avoids a blunt cast of the wire code, and also refrains from relaying
the full Error() message to the peer.

Author: jtobin

rfq/negotiator.go

@@ -513,7 +513,7 @@ func createCustomRejectErr(err error) rfqmsg.RejectErr {
 		// The rejection message will state that the oracle doesn't
 		// support the asset.
 		case ErrUnsupportedOracleAsset:
-			msg := oracleError.Error()
+			msg := oracleError.Msg
 			return rfqmsg.ErrRejectWithCustomMsg(msg)
 
 		// The rejection message will be opaque, with the error

rfq/oracle.go

@@ -371,7 +371,7 @@ func (r *RpcPriceOracle) QuerySellPrice(ctx context.Context,
 		return &OracleResponse{
 			Err: &OracleError{
 				Msg:  result.Error.Message,
-				Code: OracleErrorCode(result.Error.Code),
+				Code: marshallErrorCode(result.Error.Code),
 			},
 		}, nil
 
@@ -380,6 +380,19 @@ func (r *RpcPriceOracle) QuerySellPrice(ctx context.Context,
 	}
 }
 
+// marshallErrorCode marshalls an over-the-wire error code into an
+// OracleErrorCode.
+func marshallErrorCode(code oraclerpc.ErrorCode) OracleErrorCode {
+	switch code {
+	case oraclerpc.ErrorCode_ERROR_UNSPECIFIED:
+		return ErrUnspecifiedOracleError
+	case oraclerpc.ErrorCode_ERROR_UNSUPPORTED:
+		return ErrUnsupportedOracleAsset
+	default:
+		return ErrUnspecifiedOracleError
+	}
+}
+
 // QueryBuyPrice returns a buy price for the given asset amount.
 func (r *RpcPriceOracle) QueryBuyPrice(ctx context.Context,
 	assetSpecifier asset.Specifier, assetMaxAmt fn.Option[uint64],
@@ -483,7 +496,7 @@ func (r *RpcPriceOracle) QueryBuyPrice(ctx context.Context,
 		return &OracleResponse{
 			Err: &OracleError{
 				Msg:  result.Error.Message,
-				Code: OracleErrorCode(result.Error.Code),
+				Code: marshallErrorCode(result.Error.Code),
 			},
 		}, nil