kubectl --prune -n <namespace> doesn't visit the CLI-specified namespace.

[kinghajj]

What happened:

While testing out the --prune flag, I created a manifest with the following contents:

apiVersion: v1
kind: Namespace
metadata:
  labels:
    app: woot
    env: woot
  name: woot
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: woot
    env: woot
  name: woot
  namespace: woot
spec:
  replicas: 1
  selector:
    matchLabels:
      app: woot
      env: woot
  template:
    metadata:
      labels:
        app: woot
        env: woot
    spec:
      containers:
      - command:
        - bash
        - -c
        - while true; do date; sleep 1; done
        image: bitnami/minideb:buster
        name: woot

I ran kubectl -n woot -R -f ./manifests --prune -l env=woot, and the resources appeared on my minikube cluster:

NAME                    READY   STATUS    RESTARTS   AGE
woot-5dbccd5689-h78pg   1/1     Running   0          9s

Then, I removed the deployment from the manifest:

apiVersion: v1
kind: Namespace
metadata:
  labels:
    app: woot
    env: woot
  name: woot

And re-ran the same command, kubectl -n woot -R -f ./manifests --prune -l env=woot. To my surprise, however, the deployment wasn't removed; the only output from kubectl was namespace/woot unchanged.

What you expected to happen:

I expected the pruner to find the deployment with the matching label, env=woot, and prune it.

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

I believe my example above is minimal and easily reproducible.

Anything else we need to know?:

This small change to the code for kubectl apply resolves the issue:

diff --git a/staging/src/k8s.io/kubectl/pkg/cmd/apply/apply.go b/staging/src/k8s.io/kubectl/pkg/cmd/apply/apply.go
index 915f055ea43..67dde192a04 100644
--- a/staging/src/k8s.io/kubectl/pkg/cmd/apply/apply.go
+++ b/staging/src/k8s.io/kubectl/pkg/cmd/apply/apply.go
@@ -369,6 +369,10 @@ func (o *ApplyOptions) Run() error {
        visitedUids := sets.NewString()
        visitedNamespaces := sets.NewString()
 
+       if o.Namespace != metav1.NamespaceNone {
+               visitedNamespaces.Insert(o.Namespace)
+       }
+
        var objs []runtime.Object
 
        count := 0

Environment:

• Kubernetes version (use kubectl version): v1.16.3
• Cloud provider or hardware configuration: N/A
• OS (e.g: cat /etc/os-release): N/A
• Kernel (e.g. uname -a): N/A
• Install tools: N/A
• Network plugin and version (if this is a network-related bug): N/A
• Others: N/A

[kinghajj]

/sig cli

[MartinKaburu]

/assign @MartinKaburu
cc @soltysh @kinghajj @seans3 @mengqiy