🐛 Fakeclient: Fix status apply if existing object has managedFields set

The tracker we use in the fakeclient doesn't support status operations,
so we implemented them by copying everything but status and
ResourceVersion from the existing object.

This meant that we copied the existing objects managedFields and that in
turn made the `managedFieldsObjectTracker` error out on Apply with an
`metadata.managedFields must be nil`.

Stop copying the managedFields in status updates.

Author: alvaroaleman

pkg/client/fake/client_test.go

@@ -1834,6 +1834,41 @@ var _ = Describe("Fake client", func() {
 		Expect(initial).To(BeComparableTo(actual))
 	})
 
+	// https://github.com/kubernetes-sigs/controller-runtime/issues/3423
+	It("should be able to status apply existing objects that have managedFields set", func(ctx SpecContext) {
+		cl := NewClientBuilder().WithStatusSubresource(&corev1.Node{}).Build()
+		node := corev1applyconfigurations.Node("a-node").
+			WithSpec(corev1applyconfigurations.NodeSpec().WithPodCIDR("some-value"))
+		Expect(cl.Apply(ctx, node, client.FieldOwner("test-owner"))).To(Succeed())
+
+		node = node.
+			WithStatus(corev1applyconfigurations.NodeStatus().WithPhase(corev1.NodeRunning))
+
+		Expect(cl.Status().Apply(ctx, node, client.FieldOwner("test-owner"))).To(Succeed())
+	})
+
+	It("should not be able to manually update the fieldManager through a status update", func(ctx SpecContext) {
+		node := &corev1.Node{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: "node",
+			},
+			Spec: corev1.NodeSpec{
+				PodCIDR: "old-cidr",
+			},
+		}
+		cl := NewClientBuilder().WithStatusSubresource(&corev1.Node{}).WithObjects(node).WithReturnManagedFields().Build()
+		node.Spec.PodCIDR = "new-cidr"
+		Expect(cl.Update(ctx, node, client.FieldOwner("spec-owner"))).To(Succeed())
+
+		node.ManagedFields = []metav1.ManagedFieldsEntry{{}}
+		node.Status.Phase = corev1.NodeRunning
+
+		Expect(cl.Status().Update(ctx, node, client.FieldOwner("status-owner"))).To(Succeed())
+		Expect(node.ManagedFields).To(HaveLen(2))
+		Expect(node.ManagedFields[0].Manager).To(Equal("spec-owner"))
+		Expect(node.ManagedFields[1].Manager).To(Equal("status-owner"))
+	})
+
 	It("should Unmarshal the schemaless object with int64 to preserve ints", func(ctx SpecContext) {
 		schemeBuilder := &scheme.Builder{GroupVersion: schema.GroupVersion{Group: "test", Version: "v1"}}
 		schemeBuilder.Register(&WithSchemalessSpec{})

pkg/client/fake/versioned_tracker.go

@@ -231,15 +231,17 @@ func (t versionedTracker) updateObject(
 	}
 
 	if t.withStatusSubresource.Has(gvk) {
-		if isStatus { // copy everything but status and metadata.ResourceVersion from original object
+		if isStatus { // copy everything but status, managedFields and metadata.ResourceVersion from original object
 			if err := copyStatusFrom(obj, oldObject); err != nil {
 				return nil, false, fmt.Errorf("failed to copy non-status field for object with status subresouce: %w", err)
 			}
 			passedRV := accessor.GetResourceVersion()
+			passedManagedFields := accessor.GetManagedFields()
 			if err := copyFrom(oldObject, obj); err != nil {
 				return nil, false, fmt.Errorf("failed to restore non-status fields: %w", err)
 			}
 			accessor.SetResourceVersion(passedRV)
+			accessor.SetManagedFields(passedManagedFields)
 		} else { // copy status from original object
 			if err := copyStatusFrom(oldObject, obj); err != nil {
 				return nil, false, fmt.Errorf("failed to copy the status for object with status subresource: %w", err)