Navigation: handle case when there is no alerting node at all (#64941)

* handle case when there is no alerting node at all

* update backend tests

pkg/services/navtree/navtreeimpl/applinks.go

@@ -226,19 +226,22 @@ func (s *ServiceImpl) addPluginToSection(c *contextmodel.ReqContext, treeRoot *n
 				Url:        s.cfg.AppSubURL + "/monitoring",
 			})
 		case navtree.NavIDAlertsAndIncidents:
+			alertsAndIncidentsChildren := []*navtree.NavLink{}
 			if alertingNode != nil {
-				treeRoot.AddSection(&navtree.NavLink{
-					Text:       "Alerts & incidents",
-					Id:         navtree.NavIDAlertsAndIncidents,
-					SubTitle:   "Alerting and incident management apps",
-					Icon:       "bell",
-					Section:    navtree.NavSectionCore,
-					SortWeight: navtree.WeightAlertsAndIncidents,
-					Children:   []*navtree.NavLink{alertingNode, appLink},
-					Url:        s.cfg.AppSubURL + "/alerts-and-incidents",
-				})
+				alertsAndIncidentsChildren = append(alertsAndIncidentsChildren, alertingNode)
 				treeRoot.RemoveSection(alertingNode)
 			}
+			alertsAndIncidentsChildren = append(alertsAndIncidentsChildren, appLink)
+			treeRoot.AddSection(&navtree.NavLink{
+				Text:       "Alerts & incidents",
+				Id:         navtree.NavIDAlertsAndIncidents,
+				SubTitle:   "Alerting and incident management apps",
+				Icon:       "bell",
+				Section:    navtree.NavSectionCore,
+				SortWeight: navtree.WeightAlertsAndIncidents,
+				Children:   alertsAndIncidentsChildren,
+				Url:        s.cfg.AppSubURL + "/alerts-and-incidents",
+			})
 		default:
 			s.log.Error("Plugin app nav id not found", "pluginId", plugin.ID, "navId", sectionID)
 		}

pkg/services/navtree/navtreeimpl/applinks_test.go

@@ -240,19 +240,34 @@ func TestAddAppLinks(t *testing.T) {
 		alertsAndIncidentsNode := treeRoot.FindById(navtree.NavIDAlertsAndIncidents)
 		require.Nil(t, alertsAndIncidentsNode)
 
-		// If there is no 'Alerting' node in the navigation (= alerting not enabled) then we don't auto-create the 'Alerts and Incidents' section
+		// It should appear and once an app tries to register to it and the `Alerting` nav node is present
 		treeRoot = navtree.NavTreeRoot{}
+		treeRoot.AddSection(&navtree.NavLink{Id: navtree.NavIDAlerting, Text: "Alerting"})
 		service.navigationAppConfig = map[string]NavigationAppConfig{
 			"test-app1": {SectionID: navtree.NavIDAlertsAndIncidents},
 		}
 		err = service.addAppLinks(&treeRoot, reqCtx)
 		require.NoError(t, err)
 		alertsAndIncidentsNode = treeRoot.FindById(navtree.NavIDAlertsAndIncidents)
+		require.NotNil(t, alertsAndIncidentsNode)
+		require.Len(t, alertsAndIncidentsNode.Children, 2)
+		require.Equal(t, "Alerting", alertsAndIncidentsNode.Children[0].Text)
+		require.Equal(t, "Test app1 name", alertsAndIncidentsNode.Children[1].Text)
+	})
+
+	t.Run("Should add a 'Alerts and Incidents' section if a plugin exists that wants to live there even without an alerting node", func(t *testing.T) {
+		service.features = featuremgmt.WithFeatures(featuremgmt.FlagTopnav)
+		service.navigationAppConfig = map[string]NavigationAppConfig{}
+
+		// Check if the 'Alerts and Incidents' section is not there if no apps try to register to it
+		treeRoot := navtree.NavTreeRoot{}
+		err := service.addAppLinks(&treeRoot, reqCtx)
+		require.NoError(t, err)
+		alertsAndIncidentsNode := treeRoot.FindById(navtree.NavIDAlertsAndIncidents)
 		require.Nil(t, alertsAndIncidentsNode)
 
-		// It should appear and once an app tries to register to it and the `Alerting` nav node is present
+		// If there is no 'Alerting' node in the navigation then we still auto-create the 'Alerts and Incidents' section when a plugin wants to live there
 		treeRoot = navtree.NavTreeRoot{}
-		treeRoot.AddSection(&navtree.NavLink{Id: navtree.NavIDAlerting, Text: "Alerting"})
 		service.navigationAppConfig = map[string]NavigationAppConfig{
 			"test-app1": {SectionID: navtree.NavIDAlertsAndIncidents},
 		}
@@ -260,9 +275,8 @@ func TestAddAppLinks(t *testing.T) {
 		require.NoError(t, err)
 		alertsAndIncidentsNode = treeRoot.FindById(navtree.NavIDAlertsAndIncidents)
 		require.NotNil(t, alertsAndIncidentsNode)
-		require.Len(t, alertsAndIncidentsNode.Children, 2)
-		require.Equal(t, "Alerting", alertsAndIncidentsNode.Children[0].Text)
-		require.Equal(t, "Test app1 name", alertsAndIncidentsNode.Children[1].Text)
+		require.Len(t, alertsAndIncidentsNode.Children, 1)
+		require.Equal(t, "Test app1 name", alertsAndIncidentsNode.Children[0].Text)
 	})
 
 	t.Run("Should be able to control app sort order with SortWeight (smaller SortWeight displayed first)", func(t *testing.T) {