applyconfiguration generator uses a different variable name

[terinjokes]

In #818 support for generating ApplyConfiguration was added via the applyconfiguration generator. However, it uses different variable name (SchemeGroupVersion) than the name generated by kubebuilder (GroupVersion). This results in a build failures out of the box.

# sigs.k8s.io/controller-tools/pkg/applyconfiguration/testdata/cronjob/api/v1/applyconfiguration
api/v1/applyconfiguration/utils.go:19:10: undefined: v1.SchemeGroupVersion

The variable name from kubebuilder is set in the groupversion_info.go template:

https://github.com/kubernetes-sigs/kubebuilder/blob/9932c89b631bb03413afe858c736613c66e07882/pkg/plugins/golang/v4/scaffolds/internal/templates/api/group.go#L68-L69

The variable name in the upstream applyconfiguration-gen is set in the GenerateType implementation:

https://github.com/kubernetes/code-generator/blob/2a635fa63960c0d6fd2461819f261ed8b9115f57/cmd/applyconfiguration-gen/generators/util.go#L127-L130

The fix for users is simple (SchemeGroupVersion = GroupVersion) but it would be nice if the files generated here work out of the box with those from kubebuilder.

[JoelSpeed]

We have no influence over the code in code-generator that we are relying on here. However, we do have influence over the loaded universe. It's possible that we could detect whether the required SchemeGroupVersion exists, and, should it not exist, mock it up from the GroupVersion.

That could be a bit fragile, so we would want to also check that the types match our expectations, but at least if we put this check in earlier, we could also add a warning if we aren't able to detect the schema.GroupVersion that we require, and bail out of the generation earlier

Edit: We are already doing something similar to make sure the correct markers for +genclient are on the types we expect.