Alerting: Fix simplified routing group by override (#86552)

* Alerting: Fix simplified routing custom group by override

Custom group by overrides for simplified routing were missing required fields
GroupBy and GroupByAll normally set during upstream Route validation.

This fix ensures those missing fields are applied to the generated routes.

* Inline GroupBy and GroupByAll initialization instead of normalize after

pkg/services/ngalert/notifier/autogen_alertmanager.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/prometheus/alertmanager/pkg/labels"
+	"github.com/prometheus/common/model"
 	"golang.org/x/exp/maps"
 
 	"github.com/grafana/grafana/pkg/infra/log"
@@ -115,12 +116,16 @@ func generateRouteFromSettings(defaultReceiver string, settings map[data.Fingerp
 			if err != nil {
 				return autogeneratedRoute{}, err
 			}
+			groupByStr := append([]string{}, models.DefaultNotificationSettingsGroupBy...)
+			groupByAll, groupBy := toGroupBy(groupByStr...)
 			receiverRoute = &definitions.Route{
 				Receiver:       s.Receiver,
 				ObjectMatchers: definitions.ObjectMatchers{contactMatcher},
 				Continue:       false,
 				// Since we'll have many rules from different folders using this policy, we ensure it has these necessary groupings.
-				GroupByStr: append([]string{}, models.DefaultNotificationSettingsGroupBy...),
+				GroupByStr: groupByStr,
+				GroupBy:    groupBy,
+				GroupByAll: groupByAll,
 			}
 			receiverRoutes[s.Receiver] = receiverRoute
 			autoGenRoot.Routes = append(autoGenRoot.Routes, receiverRoute)
@@ -134,12 +139,16 @@ func generateRouteFromSettings(defaultReceiver string, settings map[data.Fingerp
 		if err != nil {
 			return autogeneratedRoute{}, err
 		}
+		normalized := s.NormalizedGroupBy()
+		groupByAll, groupBy := toGroupBy(normalized...)
 		receiverRoute.Routes = append(receiverRoute.Routes, &definitions.Route{
 			Receiver:       s.Receiver,
 			ObjectMatchers: definitions.ObjectMatchers{settingMatcher},
 			Continue:       false, // Only a single setting-specific route should match.
 
-			GroupByStr:        s.NormalizedGroupBy(),
+			GroupByStr:        normalized,
+			GroupBy:           groupBy,
+			GroupByAll:        groupByAll,
 			MuteTimeIntervals: s.MuteTimeIntervals,
 			GroupWait:         s.GroupWait,
 			GroupInterval:     s.GroupInterval,
@@ -152,6 +161,19 @@ func generateRouteFromSettings(defaultReceiver string, settings map[data.Fingerp
 	}, nil
 }
 
+// toGroupBy converts the given label strings to (groupByAll, []model.LabelName) where groupByAll is true if the input
+// contains models.GroupByAll. This logic is in accordance with upstream Route.ValidateChild().
+func toGroupBy(groupByStr ...string) (groupByAll bool, groupBy []model.LabelName) {
+	for _, l := range groupByStr {
+		if l == models.GroupByAll {
+			return true, nil
+		} else {
+			groupBy = append(groupBy, model.LabelName(l))
+		}
+	}
+	return false, groupBy
+}
+
 // addToRoute adds this autogenerated route to the given route as the first top-level route under the root.
 func (ar *autogeneratedRoute) addToRoute(route *definitions.Route) error {
 	if route == nil {

pkg/services/ngalert/notifier/autogen_alertmanager_test.go

@@ -292,6 +292,9 @@ func TestAddAutogenConfig(t *testing.T) {
 				require.NoError(t, err)
 			}
 
+			// We compare against the upstream normalized route.
+			require.NoError(t, tt.expRoute.Validate())
+
 			cOpt := []cmp.Option{
 				cmpopts.IgnoreUnexported(definitions.Route{}, labels.Matcher{}),
 			}