Event, source, handler, predicates: Use generics

This change add generic versions of event, handler and predicates along
the existing ones, prefixed with `Typed`. The existing ones are left in
place under the same signature.

The `source` constructors are changed to be generic.

examples/builtins/main.go

@@ -59,14 +59,14 @@ func main() {
 	}
 
 	// Watch ReplicaSets and enqueue ReplicaSet object key
-	if err := c.Watch(source.Kind(mgr.GetCache(), &appsv1.ReplicaSet{}, &handler.EnqueueRequestForObject{})); err != nil {
+	if err := c.Watch(source.Kind(mgr.GetCache(), &appsv1.ReplicaSet{}, &handler.TypedEnqueueRequestForObject[*appsv1.ReplicaSet]{})); err != nil {
 		entryLog.Error(err, "unable to watch ReplicaSets")
 		os.Exit(1)
 	}
 
 	// Watch Pods and enqueue owning ReplicaSet key
 	if err := c.Watch(source.Kind(mgr.GetCache(), &corev1.Pod{},
-		handler.EnqueueRequestForOwner(mgr.GetScheme(), mgr.GetRESTMapper(), &appsv1.ReplicaSet{}, handler.OnlyControllerOwner()))); err != nil {
+		handler.TypedEnqueueRequestForOwner[*corev1.Pod](mgr.GetScheme(), mgr.GetRESTMapper(), &appsv1.ReplicaSet{}, handler.OnlyControllerOwner()))); err != nil {
 		entryLog.Error(err, "unable to watch Pods")
 		os.Exit(1)
 	}

pkg/builder/controller.go

@@ -30,7 +30,6 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/client/apiutil"
 	"sigs.k8s.io/controller-runtime/pkg/controller"
 	"sigs.k8s.io/controller-runtime/pkg/handler"
-	internalsource "sigs.k8s.io/controller-runtime/pkg/internal/source"
 	"sigs.k8s.io/controller-runtime/pkg/manager"
 	"sigs.k8s.io/controller-runtime/pkg/predicate"
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
@@ -56,6 +55,7 @@ const (
 type Builder struct {
 	forInput         ForInput
 	ownsInput        []OwnsInput
+	rawSources       []source.Source
 	watchesInput     []WatchesInput
 	mgr              manager.Manager
 	globalPredicates []predicate.Predicate
@@ -123,7 +123,8 @@ func (blder *Builder) Owns(object client.Object, opts ...OwnsOption) *Builder {
 
 // WatchesInput represents the information set by Watches method.
 type WatchesInput struct {
-	src              source.Source
+	obj              client.Object
+	handler          handler.EventHandler
 	predicates       []predicate.Predicate
 	objectProjection objectProjection
 }
@@ -134,13 +135,17 @@ type WatchesInput struct {
 // This is the equivalent of calling
 // WatchesRawSource(source.Kind(cache, object), eventHandler, opts...).
 func (blder *Builder) Watches(object client.Object, eventHandler handler.EventHandler, opts ...WatchesOption) *Builder {
-	input := WatchesInput{}
+	input := WatchesInput{
+		obj:     object,
+		handler: eventHandler,
+	}
 	for _, opt := range opts {
 		opt.ApplyToWatches(&input)
 	}
-	src := source.Kind(blder.mgr.GetCache(), object, eventHandler, input.predicates...)
 
-	return blder.WatchesRawSource(src, opts...)
+	blder.watchesInput = append(blder.watchesInput, input)
+
+	return blder
 }
 
 // WatchesMetadata is the same as Watches, but forces the internal cache to only watch PartialObjectMetadata.
@@ -180,13 +185,9 @@ func (blder *Builder) WatchesMetadata(object client.Object, eventHandler handler
 //
 // STOP! Consider using For(...), Owns(...), Watches(...), WatchesMetadata(...) instead.
 // This method is only exposed for more advanced use cases, most users should use one of the higher level functions.
-func (blder *Builder) WatchesRawSource(src source.Source, opts ...WatchesOption) *Builder {
-	input := WatchesInput{src: src}
-	for _, opt := range opts {
-		opt.ApplyToWatches(&input)
-	}
+func (blder *Builder) WatchesRawSource(src source.Source) *Builder {
+	blder.rawSources = append(blder.rawSources, src)
 
-	blder.watchesInput = append(blder.watchesInput, input)
 	return blder
 }
 
@@ -312,22 +313,22 @@ func (blder *Builder) doWatch() error {
 	}
 
 	// Do the watch requests
-	if len(blder.watchesInput) == 0 && blder.forInput.object == nil {
+	if len(blder.watchesInput) == 0 && blder.forInput.object == nil && len(blder.rawSources) == 0 {
 		return errors.New("there are no watches configured, controller will never get triggered. Use For(), Owns() or Watches() to set them up")
 	}
 	allPredicates := append([]predicate.Predicate(nil), blder.globalPredicates...)
 	for _, w := range blder.watchesInput {
-		// If the source of this watch is of type Kind, project it.
-		if srcKind, ok := w.src.(*internalsource.Kind); ok {
-			allPredicates := append(allPredicates, w.predicates...)
-			typeForSrc, err := blder.project(srcKind.Type, w.objectProjection)
-			if err != nil {
-				return err
-			}
-			srcKind.Type = typeForSrc
-			srcKind.Predicates = append(srcKind.Predicates, allPredicates...)
+		projected, err := blder.project(w.obj, w.objectProjection)
+		if err != nil {
+			return fmt.Errorf("failed to project for %T: %w", w.obj, err)
 		}
-		if err := blder.ctrl.Watch(w.src); err != nil {
+		allPredicates := append(allPredicates, w.predicates...)
+		if err := blder.ctrl.Watch(source.Kind(blder.mgr.GetCache(), projected, w.handler, allPredicates...)); err != nil {
+			return err
+		}
+	}
+	for _, src := range blder.rawSources {
+		if err := blder.ctrl.Watch(src); err != nil {
 			return err
 		}
 	}

pkg/controller/controller_integration_test.go

@@ -66,12 +66,12 @@ var _ = Describe("controller", func() {
 			By("Watching Resources")
 			err = instance.Watch(
 				source.Kind(cm.GetCache(), &appsv1.ReplicaSet{},
-					handler.EnqueueRequestForOwner(cm.GetScheme(), cm.GetRESTMapper(), &appsv1.Deployment{}),
+					handler.TypedEnqueueRequestForOwner[*appsv1.ReplicaSet](cm.GetScheme(), cm.GetRESTMapper(), &appsv1.Deployment{}),
 				),
 			)
 			Expect(err).NotTo(HaveOccurred())
 
-			err = instance.Watch(source.Kind(cm.GetCache(), &appsv1.Deployment{}, &handler.EnqueueRequestForObject{}))
+			err = instance.Watch(source.Kind(cm.GetCache(), &appsv1.Deployment{}, &handler.TypedEnqueueRequestForObject[*appsv1.Deployment]{}))
 			Expect(err).NotTo(HaveOccurred())
 
 			err = cm.GetClient().Get(ctx, types.NamespacedName{Name: "foo"}, &corev1.Namespace{})

pkg/controller/controller_test.go

@@ -79,7 +79,7 @@ var _ = Describe("controller.Controller", func() {
 
 			ctx, cancel := context.WithCancel(context.Background())
 			watchChan := make(chan event.GenericEvent, 1)
-			watch := &source.Channel{Source: watchChan, Handler: &handler.EnqueueRequestForObject{}}
+			watch := source.Channel(watchChan, &handler.EnqueueRequestForObject{})
 			watchChan <- event.GenericEvent{Object: &corev1.Pod{}}
 
 			reconcileStarted := make(chan struct{})

pkg/controller/example_test.go

@@ -71,7 +71,7 @@ func ExampleController() {
 	}
 
 	// Watch for Pod create / update / delete events and call Reconcile
-	err = c.Watch(source.Kind(mgr.GetCache(), &corev1.Pod{}, &handler.EnqueueRequestForObject{}))
+	err = c.Watch(source.Kind(mgr.GetCache(), &corev1.Pod{}, &handler.TypedEnqueueRequestForObject[*corev1.Pod]{}))
 	if err != nil {
 		log.Error(err, "unable to watch pods")
 		os.Exit(1)
@@ -108,7 +108,7 @@ func ExampleController_unstructured() {
 		Version: "v1",
 	})
 	// Watch for Pod create / update / delete events and call Reconcile
-	err = c.Watch(source.Kind(mgr.GetCache(), u, &handler.EnqueueRequestForObject{}))
+	err = c.Watch(source.Kind(mgr.GetCache(), u, &handler.TypedEnqueueRequestForObject[*unstructured.Unstructured]{}))
 	if err != nil {
 		log.Error(err, "unable to watch pods")
 		os.Exit(1)
@@ -139,7 +139,7 @@ func ExampleNewUnmanaged() {
 		os.Exit(1)
 	}
 
-	if err := c.Watch(source.Kind(mgr.GetCache(), &corev1.Pod{}, &handler.EnqueueRequestForObject{})); err != nil {
+	if err := c.Watch(source.Kind(mgr.GetCache(), &corev1.Pod{}, &handler.TypedEnqueueRequestForObject[*corev1.Pod]{})); err != nil {
 		log.Error(err, "unable to watch pods")
 		os.Exit(1)
 	}

pkg/event/event.go

@@ -18,38 +18,55 @@ package event
 
 import "sigs.k8s.io/controller-runtime/pkg/client"
 
-// CreateEvent is an event where a Kubernetes object was created.  CreateEvent should be generated
+// CreateEvent is an event where a Kubernetes object was created. CreateEvent should be generated
+// by a source.Source and transformed into a reconcile.Request by a handler.EventHandler.
+type CreateEvent = TypedCreateEvent[client.Object]
+
+// UpdateEvent is an event where a Kubernetes object was updated. UpdateEvent should be generated
+// by a source.Source and transformed into a reconcile.Request by an handler.EventHandler.
+type UpdateEvent = TypedUpdateEvent[client.Object]
+
+// DeleteEvent is an event where a Kubernetes object was deleted. DeleteEvent should be generated
 // by a source.Source and transformed into a reconcile.Request by an handler.EventHandler.
-type CreateEvent struct {
+type DeleteEvent = TypedDeleteEvent[client.Object]
+
+// GenericEvent is an event where the operation type is unknown (e.g. polling or event originating outside the cluster).
+// GenericEvent should be generated by a source.Source and transformed into a reconcile.Request by an
+// handler.EventHandler.
+type GenericEvent = TypedGenericEvent[client.Object]
+
+// TypedCreateEvent is an event where a Kubernetes object was created. TypedCreateEvent should be generated
+// by a source.Source and transformed into a reconcile.Request by an handler.TypedEventHandler.
+type TypedCreateEvent[T any] struct {
 	// Object is the object from the event
-	Object client.Object
+	Object T
 }
 
-// UpdateEvent is an event where a Kubernetes object was updated.  UpdateEvent should be generated
-// by a source.Source and transformed into a reconcile.Request by an handler.EventHandler.
-type UpdateEvent struct {
+// TypedUpdateEvent is an event where a Kubernetes object was updated. TypedUpdateEvent should be generated
+// by a source.Source and transformed into a reconcile.Request by an handler.TypedEventHandler.
+type TypedUpdateEvent[T any] struct {
 	// ObjectOld is the object from the event
-	ObjectOld client.Object
+	ObjectOld T
 
 	// ObjectNew is the object from the event
-	ObjectNew client.Object
+	ObjectNew T
 }
 
-// DeleteEvent is an event where a Kubernetes object was deleted.  DeleteEvent should be generated
-// by a source.Source and transformed into a reconcile.Request by an handler.EventHandler.
-type DeleteEvent struct {
+// TypedDeleteEvent is an event where a Kubernetes object was deleted. TypedDeleteEvent should be generated
+// by a source.Source and transformed into a reconcile.Request by an handler.TypedEventHandler.
+type TypedDeleteEvent[T any] struct {
 	// Object is the object from the event
-	Object client.Object
+	Object T
 
 	// DeleteStateUnknown is true if the Delete event was missed but we identified the object
 	// as having been deleted.
 	DeleteStateUnknown bool
 }
 
-// GenericEvent is an event where the operation type is unknown (e.g. polling or event originating outside the cluster).
-// GenericEvent should be generated by a source.Source and transformed into a reconcile.Request by an
-// handler.EventHandler.
-type GenericEvent struct {
+// TypedGenericEvent is an event where the operation type is unknown (e.g. polling or event originating outside the cluster).
+// TypedGenericEvent should be generated by a source.Source and transformed into a reconcile.Request by an
+// handler.TypedEventHandler.
+type TypedGenericEvent[T any] struct {
 	// Object is the object from the event
-	Object client.Object
+	Object T
 }

pkg/handler/enqueue.go

@@ -18,9 +18,11 @@ package handler
 
 import (
 	"context"
+	"reflect"
 
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/util/workqueue"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/event"
 	logf "sigs.k8s.io/controller-runtime/pkg/internal/log"
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
@@ -33,13 +35,18 @@ type empty struct{}
 var _ EventHandler = &EnqueueRequestForObject{}
 
 // EnqueueRequestForObject enqueues a Request containing the Name and Namespace of the object that is the source of the Event.
-// (e.g. the created / deleted / updated objects Name and Namespace).  handler.EnqueueRequestForObject is used by almost all
+// (e.g. the created / deleted / updated objects Name and Namespace). handler.EnqueueRequestForObject is used by almost all
 // Controllers that have associated Resources (e.g. CRDs) to reconcile the associated Resource.
-type EnqueueRequestForObject struct{}
+type EnqueueRequestForObject = TypedEnqueueRequestForObject[client.Object]
+
+// TypedEnqueueRequestForObject enqueues a Request containing the Name and Namespace of the object that is the source of the Event.
+// (e.g. the created / deleted / updated objects Name and Namespace).  handler.TypedEnqueueRequestForObject is used by almost all
+// Controllers that have associated Resources (e.g. CRDs) to reconcile the associated Resource.
+type TypedEnqueueRequestForObject[T client.Object] struct{}
 
 // Create implements EventHandler.
-func (e *EnqueueRequestForObject) Create(ctx context.Context, evt event.CreateEvent, q workqueue.RateLimitingInterface) {
-	if evt.Object == nil {
+func (e *TypedEnqueueRequestForObject[T]) Create(ctx context.Context, evt event.TypedCreateEvent[T], q workqueue.RateLimitingInterface) {
+	if isNil(evt.Object) {
 		enqueueLog.Error(nil, "CreateEvent received with no metadata", "event", evt)
 		return
 	}
@@ -50,14 +57,14 @@ func (e *EnqueueRequestForObject) Create(ctx context.Context, evt event.CreateEv
 }
 
 // Update implements EventHandler.
-func (e *EnqueueRequestForObject) Update(ctx context.Context, evt event.UpdateEvent, q workqueue.RateLimitingInterface) {
+func (e *TypedEnqueueRequestForObject[T]) Update(ctx context.Context, evt event.TypedUpdateEvent[T], q workqueue.RateLimitingInterface) {
 	switch {
-	case evt.ObjectNew != nil:
+	case !isNil(evt.ObjectNew):
 		q.Add(reconcile.Request{NamespacedName: types.NamespacedName{
 			Name:      evt.ObjectNew.GetName(),
 			Namespace: evt.ObjectNew.GetNamespace(),
 		}})
-	case evt.ObjectOld != nil:
+	case !isNil(evt.ObjectOld):
 		q.Add(reconcile.Request{NamespacedName: types.NamespacedName{
 			Name:      evt.ObjectOld.GetName(),
 			Namespace: evt.ObjectOld.GetNamespace(),
@@ -68,8 +75,8 @@ func (e *EnqueueRequestForObject) Update(ctx context.Context, evt event.UpdateEv
 }
 
 // Delete implements EventHandler.
-func (e *EnqueueRequestForObject) Delete(ctx context.Context, evt event.DeleteEvent, q workqueue.RateLimitingInterface) {
-	if evt.Object == nil {
+func (e *TypedEnqueueRequestForObject[T]) Delete(ctx context.Context, evt event.TypedDeleteEvent[T], q workqueue.RateLimitingInterface) {
+	if isNil(evt.Object) {
 		enqueueLog.Error(nil, "DeleteEvent received with no metadata", "event", evt)
 		return
 	}
@@ -80,8 +87,8 @@ func (e *EnqueueRequestForObject) Delete(ctx context.Context, evt event.DeleteEv
 }
 
 // Generic implements EventHandler.
-func (e *EnqueueRequestForObject) Generic(ctx context.Context, evt event.GenericEvent, q workqueue.RateLimitingInterface) {
-	if evt.Object == nil {
+func (e *TypedEnqueueRequestForObject[T]) Generic(ctx context.Context, evt event.TypedGenericEvent[T], q workqueue.RateLimitingInterface) {
+	if isNil(evt.Object) {
 		enqueueLog.Error(nil, "GenericEvent received with no metadata", "event", evt)
 		return
 	}
@@ -90,3 +97,15 @@ func (e *EnqueueRequestForObject) Generic(ctx context.Context, evt event.Generic
 		Namespace: evt.Object.GetNamespace(),
 	}})
 }
+
+func isNil(arg any) bool {
+	if v := reflect.ValueOf(arg); !v.IsValid() || ((v.Kind() == reflect.Ptr ||
+		v.Kind() == reflect.Interface ||
+		v.Kind() == reflect.Slice ||
+		v.Kind() == reflect.Map ||
+		v.Kind() == reflect.Chan ||
+		v.Kind() == reflect.Func) && v.IsNil()) {
+		return true
+	}
+	return false
+}