Usage of client-go's discovery.ErrGroupDiscoveryFailed breaks apimachinery errors.IsNotFound

[saschagrunert]

The introduction of the error conversion in controller-runtime v0.15.0:

controller-runtime/pkg/client/apiutil/restmapper.go

Lines 275 to 290 in 30eae58

	for _, version := range versions {
	groupVersion := schema.GroupVersion{Group: groupName, Version: version}
	apiResourceList, err := m.client.ServerResourcesForGroupVersion(groupVersion.String())
	if err != nil {
	failedGroups[groupVersion] = err
	}
	if apiResourceList != nil {
	// even in case of error, some fallback might have been returned.
	groupVersionResources[groupVersion] = apiResourceList
	}
	}
	if len(failedGroups) > 0 {
	return nil, &discovery.ErrGroupDiscoveryFailed{Groups: failedGroups}
	}

breaks the use case of checking available APIs via k8s.io/apimachinery/pkg/api/errors.IsNotFound:

https://github.com/kubernetes/kubernetes/blob/2e306e9632b13a3c1530a7e7ddf52a50f4741523/staging/src/k8s.io/apimachinery/pkg/api/errors/errors.go#L525-L536

Reason is the error conversion, which now needs a workaround like this:
https://github.com/kubernetes-sigs/security-profiles-operator/pull/1710/files#diff-fb01936f787b03e615f35a185799e91ec41896c1fcae0991db3a24137f21cf54R78-R87

Do we want to provide an additional API or something similar to make availability checks simpler?

[alvaroaleman]

@Fedosin What is the reason for using discovery.ErrGroupDiscoveryFailed rather than just passing on the error we got from ServerResourcesForGroupVersion?

[ebensh]

@Fedosin What is the reason for using discovery.ErrGroupDiscoveryFailed rather than just passing on the error we got from ServerResourcesForGroupVersion?

Is this an approach we can take as a fix / patch? I understand that the v0.15.0 contained several changes that had the potential to break us, but detecting whether resources exist is a common operation for controllers to perform, and breaking the pattern of detecting whether a resource exists or not is a problem.

[dmitri-d]

Just encountered this issue as well.

[porridge]

Note that this also breaks use of k8s.io/apimachinery/pkg/api/meta.IsNoMatchError on the resulting error.

I wonder if this will work:
/kind bug
/kind regression

[porridge]

I've taken a stab at fixing this in #2472
Please take a look @alvaroaleman @Fedosin