fix: only send resource notification when actually deleting resources

- Modified DeleteSessionResources to track if resources were actually deleted
- Only send list_changed notification if something was removed
- Fixed race condition in TestStreamableHTTP_SessionWithResources by protecting shared state
- Added sync.Once to prevent multiple WaitGroup.Done() calls

Author: ezynda3

server/session.go

@@ -557,9 +557,13 @@ func (s *MCPServer) DeleteSessionResources(sessionID string, uris ...string) err
 		newSessionResources[k] = v
 	}
 
-	// Remove specified resources
+	// Remove specified resources and track if anything was actually deleted
+	actuallyDeleted := false
 	for _, uri := range uris {
-		delete(newSessionResources, uri)
+		if _, exists := newSessionResources[uri]; exists {
+			delete(newSessionResources, uri)
+			actuallyDeleted = true
+		}
 	}
 
 	// Set the resources (this should be thread-safe)
@@ -572,7 +576,8 @@ func (s *MCPServer) DeleteSessionResources(sessionID string, uris ...string) err
 	// For initialized sessions, honor resources.listChanged, which is specifically
 	// about whether notifications will be sent or not.
 	// see <https://modelcontextprotocol.io/specification/2025-03-26/server/resources#capabilities>
-	if session.Initialized() && s.capabilities.resources != nil && s.capabilities.resources.listChanged {
+	// Only send notification if something was actually deleted
+	if actuallyDeleted && session.Initialized() && s.capabilities.resources != nil && s.capabilities.resources.listChanged {
 		// Send notification only to this session
 		if err := s.SendNotificationToSpecificClient(sessionID, "notifications/resources/list_changed", nil); err != nil {
 			// Log the error but don't fail the operation

server/streamable_http_test.go

@@ -855,19 +855,21 @@ func TestStreamableHTTP_SessionWithTools(t *testing.T) {
 func TestStreamableHTTP_SessionWithResources(t *testing.T) {
 
 	t.Run("SessionWithResources implementation", func(t *testing.T) {
-		// Create hooks to track sessions
+		var registeredSession SessionWithResources
 		hooks := &Hooks{}
-		var registeredSession *streamableHttpSession
 		var mu sync.Mutex
 		var sessionRegistered sync.WaitGroup
+		var sessionRegisteredOnce sync.Once
 		sessionRegistered.Add(1)
 
 		hooks.AddOnRegisterSession(func(ctx context.Context, session ClientSession) {
 			if s, ok := session.(*streamableHttpSession); ok {
 				mu.Lock()
 				registeredSession = s
 				mu.Unlock()
-				sessionRegistered.Done()
+				sessionRegisteredOnce.Do(func() {
+					sessionRegistered.Done()
+				})
 			}
 		})
 
@@ -956,11 +958,21 @@ func TestStreamableHTTP_SessionWithResources(t *testing.T) {
 						},
 					},
 				}
-				registeredSession.SetSessionResources(resources)
+				mu.Lock()
+				session := registeredSession
+				mu.Unlock()
+				if session != nil {
+					session.SetSessionResources(resources)
+				}
 			}(i)
 			go func() {
 				defer wg.Done()
-				_ = registeredSession.GetSessionResources()
+				mu.Lock()
+				session := registeredSession
+				mu.Unlock()
+				if session != nil {
+					_ = session.GetSessionResources()
+				}
 			}()
 		}
 		wg.Wait()