Machine and KubeadmControlPlane disagree on k8s version validation

[mboersma]

What steps did you take and what happened:

Generate a machinepool-flavored cluster manifest:

clusterctl config cluster capz-machinepool -f machinepool --worker-machine-count 1 --kubernetes-version 1.18.3 > capz-machinepool.yaml

Then apply the manifest and get a validation error on the "version" field:

% k apply -f capz-machinepool.yaml 
cluster.cluster.x-k8s.io/capz-machinepool unchanged
azurecluster.infrastructure.cluster.x-k8s.io/capz-machinepool unchanged
azuremachinetemplate.infrastructure.cluster.x-k8s.io/capz-machinepool-control-plane created
machinepool.exp.cluster.x-k8s.io/capz-machinepool-mp-0 unchanged
azuremachinepool.exp.infrastructure.cluster.x-k8s.io/capz-machinepool-mp-0 unchanged
kubeadmconfig.bootstrap.cluster.x-k8s.io/capz-machinepool-mp-0 created
The KubeadmControlPlane "capz-machinepool-control-plane" is invalid: spec.version: Invalid value: "": spec.version in body should match '^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)([-0-9a-zA-Z_\.+]*)?$'

Adding a v prefix to v1.18.3 in the manifest fixes it, but note that:

• This worked fine until recently (until after 🐛 controlplane: Normalise image name for kube-proxy, and validate Kubernetes versions #2691?)
• the MachinePool in the same manifest is happy with either 1.18.3 or v1.18.3 AFAICT

What did you expect to happen:

I expected that CAPZ and clusterctl would create a valid manifest without built-in validation errors. Perhaps clusterctl itself should have errored rather than allow "1.18.3" through.

Anything else you would like to add:

Environment:

• Cluster-api version: v0.3.6
• Minikube/KIND version: KIND v0.7.0
• Kubernetes version: (use kubectl version): v1.18.3
• OS (e.g. from /etc/os-release):

/kind bug
[One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels]

[vincepri]

Let's reconcile the two and make sure they adhere to the same standard

cc @CecileRobertMichon @juan-lee

[CecileRobertMichon]

Is there a reason why both 1.18.3 and v1.18.3 can't be valid? It worked fine before that validation was added so is it possible that requiring the v prefix is an artificial requirement? cc @randomvariable

[randomvariable]

The decision was as a result of
#2691 (comment)

I did originally have it defaulting to add the v prefix for you.

[CecileRobertMichon]

/assign

[CecileRobertMichon]

/retitle "Machine and KubeadmControlPlane disagree on k8s version validation"

[CecileRobertMichon]

/retitle Machine and KubeadmControlPlane disagree on k8s version validation

[vincepri]

/milestone v0.3.7