Add RPCConnectionError and wrap rpc client connection errors with it

Author: Shrenuj Bansal

client.go

@@ -149,7 +149,7 @@ func httpClient(ctx context.Context, addr string, namespace string, outs []inter
 
 		hreq, err := http.NewRequest("POST", addr, bytes.NewReader(b))
 		if err != nil {
-			return clientResponse{}, err
+			return clientResponse{}, &RPCConnectionError{err}
 		}
 
 		hreq.Header = requestHeader.Clone()
@@ -162,7 +162,7 @@ func httpClient(ctx context.Context, addr string, namespace string, outs []inter
 
 		httpResp, err := _defaultHTTPClient.Do(hreq)
 		if err != nil {
-			return clientResponse{}, err
+			return clientResponse{}, &RPCConnectionError{err}
 		}
 		defer httpResp.Body.Close()
 
@@ -192,7 +192,7 @@ func websocketClient(ctx context.Context, addr string, namespace string, outs []
 	connFactory := func() (*websocket.Conn, error) {
 		conn, _, err := websocket.DefaultDialer.Dial(addr, requestHeader)
 		if err != nil {
-			return nil, xerrors.Errorf("cannot dial address %s for %w", addr, err)
+			return nil, &RPCConnectionError{xerrors.Errorf("cannot dial address %s for %w", addr, err)}
 		}
 		return conn, nil
 	}

errors.go

@@ -5,6 +5,20 @@ import (
 	"reflect"
 )
 
+const eTempWSError = -1111111
+
+type RPCConnectionError struct {
+	err error
+}
+
+func (e *RPCConnectionError) Error() string {
+	return e.err.Error()
+}
+
+func (e *RPCConnectionError) Unwrap() error {
+	return e.err
+}
+
 type Errors struct {
 	byType map[reflect.Type]ErrorCode
 	byCode map[ErrorCode]reflect.Type
@@ -17,7 +31,9 @@ const FirstUserCode = 2
 func NewErrors() Errors {
 	return Errors{
 		byType: map[reflect.Type]ErrorCode{},
-		byCode: map[ErrorCode]reflect.Type{},
+		byCode: map[ErrorCode]reflect.Type{
+			-1111111: reflect.TypeOf(RPCConnectionError{}),
+		},
 	}
 }
 

rpc_test.go

@@ -131,6 +131,30 @@ func (h *SimpleServerHandler) ErrChanSub(ctx context.Context) (<-chan int, error
 	return nil, errors.New("expect to return an error")
 }
 
+func TestRPCBadConnection(t *testing.T) {
+	// setup server
+
+	serverHandler := &SimpleServerHandler{}
+
+	rpcServer := NewServer()
+	rpcServer.Register("SimpleServerHandler", serverHandler)
+
+	// httptest stuff
+	testServ := httptest.NewServer(rpcServer)
+	defer testServ.Close()
+	// setup client
+
+	var client struct {
+		Add         func(int) error
+		AddGet      func(int) int
+		StringMatch func(t TestType, i2 int64) (out TestOut, err error)
+		ErrChanSub  func(context.Context) (<-chan int, error)
+	}
+	_, err := NewClient(context.Background(), "ws://"+testServ.Listener.Addr().String()+"0", "SimpleServerHandler", &client, nil)
+	require.True(t, errors.As(err, new(*RPCConnectionError)))
+
+}
+
 func TestRPC(t *testing.T) {
 	// setup server
 

websocket.go

@@ -19,8 +19,6 @@ const wsCancel = "xrpc.cancel"
 const chValue = "xrpc.ch.val"
 const chClose = "xrpc.ch.close"
 
-const eTempWSError = -1111111
-
 type frame struct {
 	// common
 	Jsonrpc string            `json:"jsonrpc"`