Proposal: Generics for CustomValidator & CustomDefaulter

[ahmetb]

CustomValidator and CustomDefaulter interfaces could use generics support to potentially shorten the handler funcs like this:

func (w *KubernetesPoolWebhook) ValidateUpdate(ctx context.Context, oldObj, newObj runtime.Object) (admission.Warnings, error) {
	oldO, ok := oldObj.(apiv1alpha1.KubernetesPool)
	if err != nil {
		return nil, errors.NewBadRequest(fmt.Sprintf("unexpected type %T", oldObj))
	}
	newO, ok := newObj.(apiv1alpha1.KubernetesPool)
	if err != nil {
		return nil,  errors.NewBadRequest(fmt.Sprintf("unexpected type %T", newObj))
	}
	return nil, validateUpdate(oldO, newO)
}

to

func (w *KubernetesPoolWebhook) ValidateUpdate(ctx context.Context, oldObj, newObj apiv1alpha1.KubernetesPool) (admission.Warnings, error) {
	return nil, validateUpdate(oldO, newO)
}

Also statements like:

return ctrl.NewWebhookManagedBy(mgr).
	For(&apiv1alpha1.KubernetesPool{}).
	WithDefaulter(w).
	WithValidator(w).
	Complete()

can probably be inferred with more type safety (right now there's nothing ensures a & b are handlers of the same type in WithDefaulter(a).WithDefaulter(b)?). e.g.

return ctrl.NewWebhookManagedBy[apiv1alpha1.KubernetesPool](mgr).
	WithDefaulter(w).
	WithValidator(w).
	Complete()

/kind proposal
/kind feature

[k8s-ci-robot]

@ahmetb: The label(s) kind/proposal cannot be applied, because the repository doesn't have them.

In response to this:

CustomValidator and CustomDefaulter interfaces could use generics support to potentially shorten the handler funcs like this:

func (w *KubernetesPoolWebhook) ValidateUpdate(ctx context.Context, oldObj, newObj runtime.Object) (admission.Warnings, error) {
  oldO, ok := oldObj.(apiv1alpha1.KubernetesPool)
  if err != nil {
  	return nil, errors.NewBadRequest(fmt.Sprintf("unexpected type %T", oldObj))
  }
  newO, ok := newObj.(apiv1alpha1.KubernetesPool)
  if err != nil {
  	return nil,  errors.NewBadRequest(fmt.Sprintf("unexpected type %T", newObj))
  }
  return nil, validateUpdate(oldO, newO)
}

to

func (w *KubernetesPoolWebhook) ValidateUpdate(ctx context.Context, oldObj, newObj apiv1alpha1.KubernetesPool) (admission.Warnings, error) {
  return nil, validateUpdate(oldO, newO)
}

Also statements like:

return ctrl.NewWebhookManagedBy(mgr).
  For(&apiv1alpha1.KubernetesPool{}).
  WithDefaulter(w).
  WithValidator(w).
  Complete()

can probably be inferred with more type safety (right now there's nothing ensures a & b are handlers of the same type in WithDefaulter(a).WithDefaulter(b)?).

/kind proposal
/kind feature

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[alvaroaleman]

@ahmetb are you sure this is possible? My understanding is that it isn't due to golang/go#49085, the WebhookBuilder would only be able to support one type. I'd love to be wrong on this though.

[ahmetb]

I will give it a shot. I hit that in porting go-linq to generics as well.