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Proposal: Generics for CustomValidator & CustomDefaulter #2675
Description
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
Activity
k8s-ci-robot commentedon Feb 7, 2024
@ahmetb: The label(s)
kind/proposalcannot be applied, because the repository doesn't have them.Details
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alvaroaleman commentedon Feb 8, 2024
@ahmetb are you sure this is possible? My understanding is that it isn't due to golang/go#49085, the
WebhookBuilderwould only be able to support one type. I'd love to be wrong on this though.ahmetb commentedon Feb 9, 2024
I will give it a shot. I hit that in porting go-linq to generics as well.
k8s-triage-robot commentedon May 9, 2024
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/lifecycle stale
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/lifecycle rotten
sbueringer commentedon Jun 18, 2024
/remove-lifecycle rotten
k8s-triage-robot commentedon Sep 16, 2024
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/lifecycle stale
k8s-triage-robot commentedon Oct 16, 2024
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/lifecycle rotten
k8s-triage-robot commentedon Nov 15, 2024
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/close not-planned
k8s-ci-robot commentedon Nov 15, 2024
@k8s-triage-robot: Closing this issue, marking it as "Not Planned".
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alvaroaleman commentedon Oct 16, 2025
/reopen
/lifecycle frozen
Currently also running into this and its annoying. I just had a look at all of this and I think this is totally possible, it is just that the typing changes would need to go up until including the webhook builder. Since the webhook builder conceptionally represents a webhook for one type, that seems fine
sbueringer commentedon Oct 20, 2025
+1 Makes sense to me. We might have to add new builder methods to keep supporting the Custom* interfaces until they are removed but that's fine for me (I think that depends on if we use the generic type parameter for For or not).
We could also maybe add a type parameter and only use it for defaulter/validator and once the Custom* interfaces are gone we also use it in For