[kubectl-plugin][Refactor] Standardize namespace resolution to respect kubeconfig context

[justinyeh1995]

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• I searched the issues and found no similar issues.

KubeRay Component

kubectl-plugin

Description

This is a follow up issue for #4291 (comment).
The kubectl-plugin has inconsistent namespace resolution patterns that all fail to respect the active kubeconfig context.

Current Behavior

Many Complete functions in get cluster, get workergroup, get nodes, delete, scale, and shell completion uses

if namespace == "" {
    namespace = "default"
}

Also in create cluster

namespace := "default"

These hardcoded values ignore the user's current kubeconfig context namespace.

Expected Behavior

All commands should consistently use the Factory's namespace resolution to respect kubeconfig context.

namespace, _, err := f.ToRawKubeConfigLoader().Namespace()
if err != nil {
    // error handling
}

Some examples of using Factory's namespace resolution in the upstream kubectl includes

• https://github.com/kubernetes/kubernetes/blob/d719bc771fbf7090c74430b918f8d35871eaf64c/staging/src/k8s.io/kubectl/pkg/cmd/get/get.go#L197-L212
• https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/kubectl/pkg/util/completion/completion.go#L245

Affected Areas

Hardcode in completion functions:

• pkg/util/completion/completion.go (workerGroupCompletionFunc, nodeCompletionFunc)

Hardcode in Complete():

• pkg/cmd/get/get_cluster.go
• pkg/cmd/get/get_workergroup.go
• pkg/cmd/get/get_nodes.go
• pkg/cmd/get/get_token.go
• pkg/cmd/create/create_workergroup.go
• pkg/cmd/delete/delete.go
• pkg/cmd/scale/scale_cluster.go
• pkg/cmd/job/job_submit.go
• pkg/cmd/log/log.go
• pkg/cmd/session/session.go

resolveNamespace() in Run():

• pkg/cmd/create/create_cluster.go

There might be more, so would appreciate checking more closely during implementation.

Are you willing to submit a PR?

• Yes I am willing to submit a PR!