⚠️ Change .status.replicas fields to pointer + omitempty (#12250)

* Change .status.replicas fields to pointer + omitempty

* Fix review finding, update migration doc

Author: sbueringer

api/v1beta1/conversion_test.go

@@ -275,6 +275,11 @@ func hubMachineSetStatus(in *clusterv1.MachineSetStatus, c fuzz.Continue) {
 	if in.Deprecated.V1Beta1 == nil {
 		in.Deprecated.V1Beta1 = &clusterv1.MachineSetV1Beta1DeprecatedStatus{}
 	}
+	// nil becomes &0 after hub => spoke => hub conversion
+	// This is acceptable as usually Replicas is set and controllers using older apiVersions are not writing MachineSet status.
+	if in.Replicas == nil {
+		in.Replicas = ptr.To(int32(0))
+	}
 }
 
 func spokeMachineSetStatus(in *MachineSetStatus, c fuzz.Continue) {
@@ -304,6 +309,11 @@ func hubMachineDeploymentStatus(in *clusterv1.MachineDeploymentStatus, c fuzz.Co
 	if in.Deprecated.V1Beta1 == nil {
 		in.Deprecated.V1Beta1 = &clusterv1.MachineDeploymentV1Beta1DeprecatedStatus{}
 	}
+	// nil becomes &0 after hub => spoke => hub conversion
+	// This is acceptable as usually Replicas is set and controllers using older apiVersions are not writing MachineSet status.
+	if in.Replicas == nil {
+		in.Replicas = ptr.To(int32(0))
+	}
 }
 
 func spokeMachineDeploymentSpec(in *MachineDeploymentSpec, c fuzz.Continue) {

api/v1beta1/zz_generated.conversion.go

@@ -463,7 +463,7 @@ type MachineDeploymentStatus struct {
 	// replicas is the total number of non-terminated machines targeted by this deployment
 	// (their labels match the selector).
 	// +optional
-	Replicas int32 `json:"replicas"`
+	Replicas *int32 `json:"replicas,omitempty"`
 
 	// readyReplicas is the number of ready replicas for this MachineDeployment. A machine is considered ready when Machine's Ready condition is true.
 	// +optional

api/v1beta2/machinedeployment_types.go

@@ -301,7 +301,7 @@ type MachineSetStatus struct {
 
 	// replicas is the most recently observed number of replicas.
 	// +optional
-	Replicas int32 `json:"replicas"`
+	Replicas *int32 `json:"replicas,omitempty"`
 
 	// readyReplicas is the number of ready replicas for this MachineSet. A machine is considered ready when Machine's Ready condition is true.
 	// +optional

api/v1beta2/machineset_types.go

@@ -25,6 +25,7 @@ import (
 	fuzz "github.com/google/gofuzz"
 	"k8s.io/apimachinery/pkg/api/apitesting/fuzzer"
 	runtimeserializer "k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/utils/ptr"
 
 	bootstrapv1beta1 "sigs.k8s.io/cluster-api/bootstrap/kubeadm/api/v1beta1"
 	controlplanev1 "sigs.k8s.io/cluster-api/controlplane/kubeadm/api/v1beta2"
@@ -70,6 +71,12 @@ func hubKubeadmControlPlaneStatus(in *controlplanev1.KubeadmControlPlaneStatus,
 			in.Initialization = nil
 		}
 	}
+
+	// nil becomes &0 after hub => spoke => hub conversion
+	// This is acceptable as usually Replicas is set and controllers using older apiVersions are not writing MachineSet status.
+	if in.Replicas == nil {
+		in.Replicas = ptr.To(int32(0))
+	}
 }
 
 func spokeKubeadmControlPlaneStatus(in *KubeadmControlPlaneStatus, c fuzz.Continue) {

api/v1beta2/zz_generated.deepcopy.go

@@ -650,7 +650,7 @@ type KubeadmControlPlaneStatus struct {
 	// replicas is the total number of non-terminated machines targeted by this control plane
 	// (their labels match the selector).
 	// +optional
-	Replicas int32 `json:"replicas"`
+	Replicas *int32 `json:"replicas,omitempty"`
 
 	// readyReplicas is the number of ready replicas for this KubeadmControlPlane. A machine is considered ready when Machine's Ready condition is true.
 	// +optional