From 46407e2033476b29ed9d5fa0464af3163a3b08e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Magiera?= <magik6k@gmail.com>
Date: Fri, 28 Jun 2019 16:05:10 +0200
Subject: [PATCH] rpc: client errors

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>
---
 rpclib/rpcClient.go | 44 +++++++++++++++++++++++++++++++++-----------
 rpclib/rpc_test.go  | 19 +++++++++++++++++++
 2 files changed, 52 insertions(+), 11 deletions(-)

diff --git a/rpclib/rpcClient.go b/rpclib/rpcClient.go
index 46d61b496..9b416cfc7 100644
--- a/rpclib/rpcClient.go
+++ b/rpclib/rpcClient.go
@@ -4,11 +4,24 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"net/http"
 	"reflect"
 	"sync/atomic"
 )
 
+type ErrClient struct {
+	err error
+}
+
+func (e *ErrClient) Error() string {
+	return fmt.Sprintf("RPC client error: %s", e.err)
+}
+
+func (e *ErrClient) Unwrap(err error) error {
+	return e.err
+}
+
 type result reflect.Value
 
 func (r *result) UnmarshalJSON(raw []byte) error {
@@ -61,6 +74,20 @@ func NewClient(addr string, namespace string, handler interface{}) {
 			return out
 		}
 
+		processError := func(err error) []reflect.Value{
+			out := make([]reflect.Value, nout)
+
+			if valOut != -1 {
+				out[valOut] = reflect.New(ftyp.Out(valOut)).Elem()
+			}
+			if errOut != -1 {
+				out[errOut] = reflect.New(reflect.TypeOf(new(error)).Elem()).Elem()
+				out[errOut].Set(reflect.ValueOf(&ErrClient{err}))
+			}
+
+			return out
+		}
+
 		fn := reflect.MakeFunc(ftyp, func(args []reflect.Value) (results []reflect.Value) {
 			id := atomic.AddInt64(&idCtr, 1)
 			params := make([]param, len(args))
@@ -79,21 +106,18 @@ func NewClient(addr string, namespace string, handler interface{}) {
 
 			b, err := json.Marshal(&req)
 			if err != nil {
-				// TODO: try returning an error if the method has one
-				panic(err)
+				return processError(err)
 			}
 
 			httpResp, err := http.Post(addr, "application/json", bytes.NewReader(b))
 			if err != nil {
-				// TODO: try returning an error if the method has one
-				panic(err)
+				return processError(err)
 			}
 			defer httpResp.Body.Close()
 
+			// TODO: check error codes in spec
 			if httpResp.StatusCode != 200 {
-				// TODO: try returning an error if the method has one
-				// TODO: actually parse response, it haz right errors
-				panic("non 200 code")
+				return processError(errors.New("non 200 response code"))
 			}
 
 			var resp clientResponse
@@ -102,13 +126,11 @@ func NewClient(addr string, namespace string, handler interface{}) {
 			}
 
 			if err := json.NewDecoder(httpResp.Body).Decode(&resp); err != nil {
-				// TODO: try returning an error if the method has one
-				panic(err)
+				return processError(err)
 			}
 
 			if resp.Id != *req.Id {
-				// TODO: try returning an error if the method has one
-				panic("request and response id didn't match")
+				return processError(errors.New("request and response id didn't match"))
 			}
 
 			return processResponse(resp)
diff --git a/rpclib/rpc_test.go b/rpclib/rpc_test.go
index fd387cf4a..6f8a9d143 100644
--- a/rpclib/rpc_test.go
+++ b/rpclib/rpc_test.go
@@ -142,4 +142,23 @@ func TestRPC(t *testing.T) {
 	// shouldn't panic
 	noparam.Add()
 
+	var erronly struct {
+		Add func() error
+	}
+	NewClient(testServ.URL, "SimpleServerHandler", &erronly)
+
+	err = erronly.Add()
+	if err == nil || err.Error() != "RPC client error: non 200 response code" {
+		t.Error("wrong error")
+	}
+
+	var wrongtype struct {
+		Add func(string) error
+	}
+	NewClient(testServ.URL, "SimpleServerHandler", &wrongtype)
+
+	err = wrongtype.Add("not an int")
+	if err == nil || err.Error() != "RPC client error: non 200 response code" {
+		t.Error("wrong error")
+	}
 }