rpcsrv: return ErrUnknownSession and ErrUnknownIterator

Behaviour change.
`terminatesession` returns ErrUnknownSession in case of impossibility of finding session,
previously there was no-error response with `false` result.
`traverseIterator`returns ErrUnknownSession in case of impossibility of finding session,
previously there was no-error response with default result; `traverseIterator`returns ErrUnknownIterator,
there were no such errors before.
Accordingly to proposal:
https://github.com/neo-project/proposals/pull/156
Also adding description of `traverseIterator` in docs/rpc.md.

Signed-off-by: Tatiana Nesterenko <tatiana@nspcc.io>

docs/rpc.md

@@ -196,6 +196,11 @@ enabled in the server's protocol configuration.
 ##### `getnep11transfers` and `getnep17transfers`
 `transfernotifyindex` is not tracked by NeoGo, thus this field is always zero.
 
+##### `traverseiterator` and `terminatesession`
+
+NeoGo returns an error when it is unable to find a session or iterator, unlike 
+the error-free C# response that provides a default result.
+
 ##### `verifyProof`
 
 NeoGo can generate an error in response to an invalid proof, unlike

pkg/services/rpcsrv/client_test.go

@@ -1723,7 +1723,8 @@ func TestClient_IteratorSessions(t *testing.T) {
 			require.True(t, ok)
 
 			ok, err = c.TerminateSession(sID)
-			require.NoError(t, err)
+			require.Error(t, err)
+			require.ErrorIs(t, err, neorpc.ErrUnknownSession)
 			require.False(t, ok) // session has already been terminated.
 		})
 		t.Run("automatically", func(t *testing.T) {
@@ -1746,7 +1747,8 @@ func TestClient_IteratorSessions(t *testing.T) {
 				time.Duration(rpcSrv.config.SessionExpirationTime)*time.Second/4)
 
 			ok, err := c.TerminateSession(sID)
-			require.NoError(t, err)
+			require.Error(t, err)
+			require.ErrorIs(t, err, neorpc.ErrUnknownSession)
 			require.False(t, ok) // session has already been terminated.
 		})
 	})

pkg/services/rpcsrv/server.go

@@ -2351,7 +2351,7 @@ func (s *Server) traverseIterator(reqParams params.Params) (any, *neorpc.Error)
 	session, ok := s.sessions[sID.String()]
 	if !ok {
 		s.sessionsLock.Unlock()
-		return []json.RawMessage{}, nil
+		return nil, neorpc.ErrUnknownSession
 	}
 	session.iteratorsLock.Lock()
 	// Perform `till` update only after session.iteratorsLock is taken in order to have more
@@ -2362,14 +2362,19 @@ func (s *Server) traverseIterator(reqParams params.Params) (any, *neorpc.Error)
 	var (
 		iIDStr = iID.String()
 		iVals  []stackitem.Item
+		found  bool
 	)
 	for _, it := range session.iteratorIdentifiers {
 		if iIDStr == it.ID {
 			iVals = iterator.Values(it.Item, count)
+			found = true
 			break
 		}
 	}
 	session.iteratorsLock.Unlock()
+	if !found {
+		return nil, neorpc.ErrUnknownIterator
+	}
 
 	result := make([]json.RawMessage, len(iVals))
 	for j := range iVals {
@@ -2393,7 +2398,9 @@ func (s *Server) terminateSession(reqParams params.Params) (any, *neorpc.Error)
 	s.sessionsLock.Lock()
 	defer s.sessionsLock.Unlock()
 	session, ok := s.sessions[strSID]
-	if ok {
+	if !ok {
+		return nil, neorpc.ErrUnknownSession
+	}
 	// Iterators access Seek channel under the hood; finalizer closes this channel, thus,
 	// we need to perform finalisation under iteratorsLock.
 	session.iteratorsLock.Lock()
@@ -2403,7 +2410,6 @@ func (s *Server) terminateSession(reqParams params.Params) (any, *neorpc.Error)
 	}
 	delete(s.sessions, strSID)
 	session.iteratorsLock.Unlock()
-	}
 	return ok, nil
 }
 

pkg/services/rpcsrv/server_test.go

@@ -2582,6 +2582,13 @@ func testRPCProtocol(t *testing.T, doRPCCall func(string, string, *testing.T) []
 		return res.Session, *iterator.ID
 	}
 	t.Run("traverseiterator", func(t *testing.T) {
+		t.Run("sessions disabled", func(t *testing.T) {
+			_, _, httpSrv2 := initClearServerWithCustomConfig(t, func(c *config.Config) {
+				c.ApplicationConfiguration.RPC.SessionEnabled = false
+			})
+			body := doRPCCall(`{"jsonrpc": "2.0", "id": 1, "method": "traverseiterator", "params": []}"`, httpSrv2.URL, t)
+			checkErrGetResult(t, body, true, neorpc.ErrSessionsDisabledCode)
+		})
 		t.Run("good", func(t *testing.T) {
 			sID, iID := prepareIteratorSession(t)
 			expectedCount := 99
@@ -2626,36 +2633,35 @@ func testRPCProtocol(t *testing.T, doRPCCall func(string, string, *testing.T) []
 			_, iID := prepareIteratorSession(t)
 			rpc := fmt.Sprintf(`{"jsonrpc": "2.0", "id": 1, "method": "traverseiterator", "params": ["%s", "%s", %d]}"`, uuid.NewString(), iID.String(), 1)
 			body := doRPCCall(rpc, httpSrv.URL, t)
-			resp := checkErrGetResult(t, body, false, 0)
+			checkErrGetResult(t, body, true, neorpc.ErrUnknownSessionCode)
-			res := new([]json.RawMessage)
-			require.NoError(t, json.Unmarshal(resp, res))
-			require.Equal(t, 0, len(*res)) // No errors expected, no elements should be returned.
 		})
 		t.Run("unknown iterator", func(t *testing.T) {
 			sID, _ := prepareIteratorSession(t)
 			rpc := fmt.Sprintf(`{"jsonrpc": "2.0", "id": 1, "method": "traverseiterator", "params": ["%s", "%s", %d]}"`, sID.String(), uuid.NewString(), 1)
 			body := doRPCCall(rpc, httpSrv.URL, t)
-			resp := checkErrGetResult(t, body, false, 0)
+			checkErrGetResult(t, body, true, neorpc.ErrUnknownIteratorCode)
-			res := new([]json.RawMessage)
-			require.NoError(t, json.Unmarshal(resp, res))
-			require.Equal(t, 0, len(*res)) // No errors expected, no elements should be returned.
 		})
 	})
 	t.Run("terminatesession", func(t *testing.T) {
-		check := func(t *testing.T, id string, expected bool) {
+		rpc := `{"jsonrpc": "2.0", "id": 1, "method": "terminatesession", "params": ["%s"]}"`
-			rpc := fmt.Sprintf(`{"jsonrpc": "2.0", "id": 1, "method": "terminatesession", "params": ["%s"]}"`, id)
+		t.Run("sessions disabled", func(t *testing.T) {
-			body := doRPCCall(rpc, httpSrv.URL, t)
+			_, _, httpSrv2 := initClearServerWithCustomConfig(t, func(c *config.Config) {
+				c.ApplicationConfiguration.RPC.SessionEnabled = false
+			})
+			body := doRPCCall(fmt.Sprintf(rpc, uuid.NewString()), httpSrv2.URL, t)
+			checkErrGetResult(t, body, true, neorpc.ErrSessionsDisabledCode)
+		})
+		t.Run("true", func(t *testing.T) {
+			sID, _ := prepareIteratorSession(t)
+			body := doRPCCall(fmt.Sprintf(rpc, sID.String()), httpSrv.URL, t)
 			resp := checkErrGetResult(t, body, false, 0)
 			res := new(bool)
 			require.NoError(t, json.Unmarshal(resp, res))
-			require.Equal(t, expected, *res)
+			require.Equal(t, true, *res)
-		}
-		t.Run("true", func(t *testing.T) {
-			sID, _ := prepareIteratorSession(t)
-			check(t, sID.String(), true)
 		})
 		t.Run("false", func(t *testing.T) {
-			check(t, uuid.NewString(), false)
+			body := doRPCCall(fmt.Sprintf(rpc, uuid.NewString()), httpSrv.URL, t)
+			checkErrGetResult(t, body, true, neorpc.ErrUnknownSessionCode)
 		})
 		t.Run("expired", func(t *testing.T) {
 			_, _ = prepareIteratorSession(t)