ExecCredentialSpec.Cluster. config is missing

[wkloucek]

What happened (please include outputs or screenshots):

#2298 / #2303 implemented the provideClusterInfo.

It misses this part (from https://kubernetes.io/docs/reference/config-api/client-authentication.v1/#client-authentication-k8s-io-v1-Cluster):

Config holds additional config data that is specific to the exec plugin with regards to the cluster being authenticated to.

This data is sourced from the clientcmd Cluster object's extensions[client.authentication.k8s.io/exec] field:
...
...

What you expected to happen:

client.authentication.k8s.io/exec extension is set to ExecCredentialSpec.Cluster.config so that gardenlogin can use it

How to reproduce it (as minimally and precisely as possible):

Unfortunately I only know how to reproduce it with a Gardener Kubernetes setup.

Setup the KUBECONFIG environment:

• gardenctl target --garden xxx --project xxx --shoot xxx
• eval $(gardenctl kubectl-env zsh) -> this sets KUBECONFIG to a file, that looks like this: https://github.com/gardener/gardenlogin/blob/42df32af80451062f81c015c5e89a109c821e463/README.md?plain=1#L86-L99

Then run following script:

from kubernetes import client, config

# Configs can be set in Configuration class directly or using helper utility
config.load_kube_config()

v1 = client.CoreV1Api()
print("Listing pods with their IPs:")
ret = v1.list_namespaced_pod(namespace="default", watch=False)
for i in ret.items:
    print("%s\t%s\t%s" % (i.status.pod_ip, i.metadata.namespace, i.metadata.name))

You'll get an error:

'ERROR:root:exec: process returned 1. Error: name must be specified. Hint: update kubectl in case you are using a version older than v1.20.0
Usage:
  gardenlogin get-client-certificate [flags
]

Flags:
...

Anything else we need to know?:

Environment:

• Kubernetes version (kubectl version):
• OS (e.g., MacOS 10.13.6):
• Python version (python --version)
• Python client version (pip list | grep kubernetes)

[roycaihw]

/assign @wkloucek