add unit tests for NewControllerDescriptors

- controller descriptors should not be feature gated
- aliases should not be defined for new controllers and have only a
  canonical name

cmd/kube-controller-manager/app/controllermanager_test.go

@@ -21,8 +21,13 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+
 	"k8s.io/apimachinery/pkg/util/sets"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	cpnames "k8s.io/cloud-provider/names"
+	"k8s.io/component-base/featuregate"
+	featuregatetesting "k8s.io/component-base/featuregate/testing"
 
 	"k8s.io/kubernetes/cmd/kube-controller-manager/names"
 )
@@ -96,3 +101,58 @@ func TestControllerNamesDeclaration(t *testing.T) {
 func TestNewControllerDescriptorsShouldNotPanic(t *testing.T) {
 	NewControllerDescriptors()
 }
+
+func TestNewControllerDescriptorsAlwaysReturnsDescriptorsForAllControllers(t *testing.T) {
+	controllersWithoutFeatureGates := KnownControllers()
+
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, "AllAlpha", true)()
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, "AllBeta", true)()
+
+	controllersWithFeatureGates := KnownControllers()
+
+	if diff := cmp.Diff(controllersWithoutFeatureGates, controllersWithFeatureGates); diff != "" {
+		t.Errorf("unexpected controllers after enabling feature gates, NewControllerDescriptors should always return all controller descriptors. Controllers should define required feature gates in ControllerDescriptor.requiredFeatureGates. Diff of returned controllers:\n%s", diff)
+	}
+}
+
+func TestFeatureGatedControllersShouldNotDefineAliases(t *testing.T) {
+	featureGateRegex := regexp.MustCompile("^([a-zA-Z0-9]+)")
+
+	alphaFeatures := sets.NewString()
+	for _, featureText := range utilfeature.DefaultFeatureGate.KnownFeatures() {
+		// we have to parse this from KnownFeatures, because usage of mutable FeatureGate is not allowed in unit tests
+		feature := featureGateRegex.FindString(featureText)
+		if strings.Contains(featureText, string(featuregate.Alpha)) && feature != "AllAlpha" {
+			alphaFeatures.Insert(feature)
+		}
+
+	}
+
+	for name, controller := range NewControllerDescriptors() {
+		if len(controller.GetAliases()) == 0 {
+			continue
+		}
+
+		requiredFeatureGates := controller.GetRequiredFeatureGates()
+		if len(requiredFeatureGates) == 0 {
+			continue
+		}
+
+		// DO NOT ADD any new controllers here. These two controllers are an exception, because they were added before this test was introduced
+		if name == names.LegacyServiceAccountTokenCleanerController || name == names.ResourceClaimController {
+			continue
+		}
+
+		areAllRequiredFeaturesAlpha := true
+		for _, feature := range requiredFeatureGates {
+			if !alphaFeatures.Has(string(feature)) {
+				areAllRequiredFeaturesAlpha = false
+				break
+			}
+		}
+
+		if areAllRequiredFeaturesAlpha {
+			t.Errorf("alias check failed: controller name %q should not be aliased as it is still guarded by alpha feature gates (%v) and thus should have only a canonical name", name, requiredFeatureGates)
+		}
+	}
+}

cmd/kube-controller-manager/app/core.go

@@ -427,7 +427,7 @@ func newResourceClaimControllerDescriptor() *ControllerDescriptor {
 		aliases:  []string{"resource-claim-controller"},
 		initFunc: startResourceClaimController,
 		requiredFeatureGates: []featuregate.Feature{
-			features.DynamicResourceAllocation,
+			features.DynamicResourceAllocation, // TODO update app.TestFeatureGatedControllersShouldNotDefineAliases when removing this feature
 		},
 	}
 }
@@ -738,7 +738,7 @@ func newLegacyServiceAccountTokenCleanerControllerDescriptor() *ControllerDescri
 		aliases:  []string{"legacy-service-account-token-cleaner"},
 		initFunc: startLegacyServiceAccountTokenCleanerController,
 		requiredFeatureGates: []featuregate.Feature{
-			features.LegacyServiceAccountTokenCleanUp,
+			features.LegacyServiceAccountTokenCleanUp, // TODO update app.TestFeatureGatedControllersShouldNotDefineAliases when removing this feature
 		},
 	}
 }