Make RPCError an actual error and don't swallow its companion data

rpc/lib/types/types.go

@@ -6,7 +6,6 @@ import (
 	"strings"
 
 	"github.com/pkg/errors"
-
 	events "github.com/tendermint/tmlibs/events"
 )
 
@@ -60,6 +59,14 @@ type RPCError struct {
 	Data    string `json:"data,omitempty"`
 }
 
+func (err RPCError) Error() string {
+	const baseFormat = "RPC error %v - %s"
+	if err.Data != "" {
+		return fmt.Sprintf(baseFormat+": %s", err.Code, err.Message, err.Data)
+	}
+	return fmt.Sprintf(baseFormat, err.Code, err.Message)
+}
+
 type RPCResponse struct {
 	JSONRPC string           `json:"jsonrpc"`
 	ID      string           `json:"id"`

rpc/lib/types/types_test.go

@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"testing"
 
+	"fmt"
+
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 )
@@ -30,3 +32,18 @@ func TestResponses(t *testing.T) {
 	i := `{"jsonrpc":"2.0","id":"2","error":{"code":-32601,"message":"Method not found"}}`
 	assert.Equal(string(h), string(i))
 }
+
+func TestRPCError(t *testing.T) {
+	assert.Equal(t, "RPC error 12 - Badness: One worse than a code 11",
+		fmt.Sprintf("%v", &RPCError{
+			Code:    12,
+			Message: "Badness",
+			Data:    "One worse than a code 11",
+		}))
+
+	assert.Equal(t, "RPC error 12 - Badness",
+		fmt.Sprintf("%v", &RPCError{
+			Code:    12,
+			Message: "Badness",
+		}))
+}