Alerting: Return 404 when /api/ruler/grafana/api/v1/rules/{Namespace}/{Groupname} does not exist (#100264)

* Return a 404 when rule group doesn't exist

* Update tests

* Update swagger doc and tests

pkg/services/ngalert/api/api_ruler.go

@@ -242,6 +242,10 @@ func (srv RulerSrv) RouteGetRulesGroupConfig(c *contextmodel.ReqContext, namespa
 		return errorToResponse(err)
 	}
 
+	if len(rules) == 0 {
+		return ErrResp(http.StatusNotFound, errors.New("rule group does not exist"), "")
+	}
+
 	provenanceRecords, err := srv.provenanceStore.GetProvenances(c.Req.Context(), c.SignedInUser.GetOrgID(), (&ngmodels.AlertRule{}).ResourceType())
 	if err != nil {
 		return ErrResp(http.StatusInternalServerError, err, "failed to get group alert rules")
@@ -251,6 +255,7 @@ func (srv RulerSrv) RouteGetRulesGroupConfig(c *contextmodel.ReqContext, namespa
 		// nolint:staticcheck
 		GettableRuleGroupConfig: toGettableRuleGroupConfig(finalRuleGroup, rules, provenanceRecords, srv.resolveUserIdToNameFn(c.Req.Context())),
 	}
+
 	return response.JSON(http.StatusAccepted, result)
 }
 

pkg/services/ngalert/api/api_ruler_test.go

@@ -694,6 +694,24 @@ func TestRouteGetRulesGroupConfig(t *testing.T) {
 			}
 		}
 	})
+	t.Run("should return a 404 when fetching a group that doesn't exist", func(t *testing.T) {
+		orgID := rand.Int63()
+		folder := randFolder()
+		ruleStore := fakes.NewRuleStore(t)
+		ruleStore.Folders[orgID] = append(ruleStore.Folders[orgID], folder)
+		groupKey := models.GenerateGroupKey(orgID)
+		groupKey.NamespaceUID = folder.UID
+
+		expectedRules := gen.With(gen.WithGroupKey(groupKey), gen.WithUniqueGroupIndex()).GenerateManyRef(5, 10)
+		ruleStore.PutRule(context.Background(), expectedRules...)
+
+		perms := createPermissionsForRules(expectedRules, orgID)
+		req := createRequestContextWithPerms(orgID, perms, nil)
+
+		response := createService(ruleStore).RouteGetRulesGroupConfig(req, folder.UID, "non-existent-rule-group")
+
+		require.Equal(t, http.StatusNotFound, response.Status())
+	})
 }
 
 func TestVerifyProvisionedRulesNotAffected(t *testing.T) {

pkg/services/ngalert/api/tooling/definitions/cortex-ruler.go

@@ -167,6 +167,7 @@ import (
 //     Responses:
 //       202: RuleGroupConfigResponse
 //       403: ForbiddenError
+//		 404: NotFound
 
 // swagger:route Get /ruler/{DatasourceUID}/api/v1/rules/{Namespace}/{Groupname} ruler RouteGetRulegGroupConfig
 //