fix a case when Limit is 0 when syncing mailservers (#29)

It also improves passing errors to the requester.

.travis.yml

@@ -2,7 +2,7 @@ notifications:
   email: false
 language: go
 go:
-- 1.10.x
+- 1.12.x
 sudo: false
 jobs:
   include:

whisperv6/doc.go

@@ -122,8 +122,12 @@ type SyncMailRequest struct {
 
 // Validate checks request's fields if they are valid.
 func (r SyncMailRequest) Validate() error {
+	if r.Limit == 0 {
+		return errors.New("invalid 'Limit' value, expected value greater than 0")
+	}
+
 	if r.Limit > MaxLimitInSyncMailRequest {
-		return fmt.Errorf("invalid 'Limit' value, expected lower than %d", MaxLimitInSyncMailRequest)
+		return fmt.Errorf("invalid 'Limit' value, expected value lower than %d", MaxLimitInSyncMailRequest)
 	}
 
 	if r.Lower > r.Upper {

whisperv6/doc_test.go

@@ -16,17 +16,18 @@ func TestSyncMailRequestValidate(t *testing.T) {
 		Error string
 	}{
 		{
-			Name: "empty request is valid",
-			Req:  SyncMailRequest{},
+			Name:  "invalid zero Limit",
+			Req:   SyncMailRequest{},
+			Error: "invalid 'Limit' value, expected value greater than 0",
 		},
 		{
-			Name:  "invalid Limit",
+			Name:  "invalid large Limit",
 			Req:   SyncMailRequest{Limit: 1e6},
-			Error: "invalid 'Limit' value, expected lower than 1000",
+			Error: "invalid 'Limit' value, expected value lower than 1000",
 		},
 		{
 			Name:  "invalid Lower",
-			Req:   SyncMailRequest{Lower: 10, Upper: 5},
+			Req:   SyncMailRequest{Limit: 10, Lower: 10, Upper: 5},
 			Error: "invalid 'Lower' value, can't be greater than 'Upper'",
 		},
 	}

whisperv6/whisper.go

@@ -1058,7 +1058,15 @@ func (whisper *Whisper) runMessageLoop(p *Peer, rw p2p.MsgReadWriter) error {
 				}
 
 				if err := whisper.mailServer.SyncMail(p, request); err != nil {
-					log.Error("failed to sync envelopes", "peer", p.peer.ID().String())
+					log.Error(
+						"failed to sync envelopes",
+						"peer", p.peer.ID().String(),
+					)
+					_ = whisper.SendSyncResponse(
+						p,
+						SyncResponse{Error: err.Error()},
+					)
+					return err
 				}
 			} else {
 				log.Debug("requested to sync messages but mail servers is not registered", "peer", p.peer.ID().String())

whisperv6/whisper_test.go

@@ -1378,7 +1378,7 @@ func TestSyncMessages(t *testing.T) {
 
 		w.peers[newPeer(w, p, rw1)] = struct{}{}
 
-		err := w.SyncMessages(p.ID().Bytes(), SyncMailRequest{Lower: 10, Upper: 5})
+		err := w.SyncMessages(p.ID().Bytes(), SyncMailRequest{Limit: 10, Lower: 10, Upper: 5})
 		require.EqualError(t, err, "invalid 'Lower' value, can't be greater than 'Upper'")
 	})
 
@@ -1392,7 +1392,7 @@ func TestSyncMessages(t *testing.T) {
 		w.peers[newPeer(w, p, rw1)] = struct{}{}
 
 		go func() {
-			err := w.SyncMessages(p.ID().Bytes(), SyncMailRequest{})
+			err := w.SyncMessages(p.ID().Bytes(), SyncMailRequest{Limit: 10})
 			require.NoError(t, err)
 		}()
 
@@ -1425,14 +1425,14 @@ func TestHandleP2PSyncRequestCode(t *testing.T) {
 	w.RegisterServer(mailMock)
 
 	go func() {
-		err := p2p.Send(rw1, p2pSyncRequestCode, SyncMailRequest{})
+		err := p2p.Send(rw1, p2pSyncRequestCode, SyncMailRequest{Limit: 10})
 		require.NoError(t, err)
 		require.NoError(t, rw1.Close())
 	}()
 
 	err := w.runMessageLoop(peer, rw2)
 	if err != nil && err != p2p.ErrPipeClosed {
-		require.FailNow(t, "invalid err", err)
+		require.FailNow(t, "invalid err", err.Error())
 	}
 
 	mailMock.AssertNumberOfCalls(t, "SyncMail", 1)
@@ -1449,7 +1449,7 @@ func TestHandleP2PSyncRequestCodeWithInvalidRequest(t *testing.T) {
 	w.RegisterServer(mailMock)
 
 	// create an invalid request
-	req := SyncMailRequest{Lower: 10, Upper: 5}
+	req := SyncMailRequest{Limit: 10, Lower: 10, Upper: 5}
 	require.Error(t, req.Validate())
 
 	go func() {