Re-implement gvkFixupWatcher as a watch.FilterFunc

Signed-off-by: Richard Wall <richard.wall@jetstack.io>

Author: wallrj

pkg/cache/internal/informers_map.go

@@ -409,41 +409,33 @@ func createMetadataListWatch(gvk schema.GroupVersionKind, ip *specificInformersM
 	}, nil
 }
 
-type gvkFixupWatcher struct {
-	watcher watch.Interface
-	ch      chan watch.Event
-	gvk     schema.GroupVersionKind
-	wg      sync.WaitGroup
-}
-
+// newGVKFixupWatcher adds a wrapper that preserves the GVK information when
+// events come in.
+//
+// This works around a bug where GVK information is not passed into mapping
+// functions when using the OnlyMetadata option in the builder.
+// This issue is most likely caused by kubernetes/kubernetes#80609.
+// See kubernetes-sigs/controller-runtime#1484.
+//
+// This was originally implemented as a cache.ResourceEventHandler wrapper but
+// that contained a data race which was resolved by setting the GVK in a watch
+// wrapper, before the objects are written to the cache.
+// See kubernetes-sigs/controller-runtime#1650.
+//
+// The original watch wrapper was found to be incompatible with
+// k8s.io/client-go/tools/cache.Reflector so it has been re-implemented as a
+// watch.Filter which is compatible.
+// See kubernetes-sigs/controller-runtime#1789.
 func newGVKFixupWatcher(gvk schema.GroupVersionKind, watcher watch.Interface) watch.Interface {
-	ch := make(chan watch.Event)
-	w := &gvkFixupWatcher{
-		gvk:     gvk,
-		watcher: watcher,
-		ch:      ch,
-	}
-	w.wg.Add(1)
-	go w.run()
-	return w
-}
-
-func (w *gvkFixupWatcher) run() {
-	for e := range w.watcher.ResultChan() {
-		e.Object.GetObjectKind().SetGroupVersionKind(w.gvk)
-		w.ch <- e
-	}
-	w.wg.Done()
-}
-
-func (w *gvkFixupWatcher) Stop() {
-	w.watcher.Stop()
-	w.wg.Wait()
-	close(w.ch)
-}
-
-func (w *gvkFixupWatcher) ResultChan() <-chan watch.Event {
-	return w.ch
+	return watch.Filter(
+		watcher,
+		func(in watch.Event) (out watch.Event, keep bool) {
+			keep = true
+			in.DeepCopyInto(&out)
+			out.Object.GetObjectKind().SetGroupVersionKind(gvk)
+			return out, keep
+		},
+	)
 }
 
 // resyncPeriod returns a function which generates a duration each time it is