add --subresource to kubectl apply

hack/testdata/pod-apply-status.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: test-pod
+status:
+  conditions:
+  - type: example.io/Foo
+    status: "True"
+    message: message
+    reason: reason
+

staging/src/k8s.io/kubectl/pkg/cmd/apply/apply.go

@@ -50,6 +50,7 @@ import (
 	"k8s.io/kubectl/pkg/util/i18n"
 	"k8s.io/kubectl/pkg/util/openapi"
 	"k8s.io/kubectl/pkg/util/prune"
+	"k8s.io/kubectl/pkg/util/slice"
 	"k8s.io/kubectl/pkg/util/templates"
 	"k8s.io/kubectl/pkg/validation"
 )
@@ -71,6 +72,7 @@ type ApplyFlags struct {
 	All            bool
 	Overwrite      bool
 	OpenAPIPatch   bool
+	Subresource    string
 
 	PruneAllowlist []string
 
@@ -97,6 +99,7 @@ type ApplyOptions struct {
 	All             bool
 	Overwrite       bool
 	OpenAPIPatch    bool
+	Subresource     string
 
 	ValidationDirective string
 	Validator           validation.Schema
@@ -178,6 +181,8 @@ var (
 
 var ApplySetToolVersion = version.Get().GitVersion
 
+var supportedSubresources = []string{"status", "scale"}
+
 // NewApplyFlags returns a default ApplyFlags
 func NewApplyFlags(streams genericiooptions.IOStreams) *ApplyFlags {
 	return &ApplyFlags{
@@ -235,6 +240,7 @@ func (flags *ApplyFlags) AddFlags(cmd *cobra.Command) {
 	cmdutil.AddPruningFlags(cmd, &flags.Prune, &flags.PruneAllowlist, &flags.All, &flags.ApplySetRef)
 	cmd.Flags().BoolVar(&flags.Overwrite, "overwrite", flags.Overwrite, "Automatically resolve conflicts between the modified and live configuration by using values from the modified configuration")
 	cmd.Flags().BoolVar(&flags.OpenAPIPatch, "openapi-patch", flags.OpenAPIPatch, "If true, use openapi to calculate diff when the openapi presents and the resource can be found in the openapi spec. Otherwise, fall back to use baked-in types.")
+	cmdutil.AddSubresourceFlags(cmd, &flags.Subresource, "If specified, apply will operate on the subresource of the requested object.  Only allowed when using --server-side.", supportedSubresources...)
 }
 
 // ToOptions converts from CLI inputs to runtime inputs
@@ -356,6 +362,7 @@ func (flags *ApplyFlags) ToOptions(f cmdutil.Factory, cmd *cobra.Command, baseNa
 		All:             flags.All,
 		Overwrite:       flags.Overwrite,
 		OpenAPIPatch:    flags.OpenAPIPatch,
+		Subresource:     flags.Subresource,
 
 		Recorder:            recorder,
 		Namespace:           namespace,
@@ -438,6 +445,12 @@ func (o *ApplyOptions) Validate() error {
 			}
 		}
 	}
+	if len(o.Subresource) > 0 && !slice.ContainsString(supportedSubresources, o.Subresource, nil) {
+		return fmt.Errorf("invalid subresource value: %q. Must be one of %v", o.Subresource, supportedSubresources)
+	}
+	if len(o.Subresource) > 0 && !o.ServerSideApply {
+		return fmt.Errorf("--subresource can only be specified for --server-side")
+	}
 
 	return nil
 }
@@ -577,7 +590,9 @@ func (o *ApplyOptions) applyOneObject(info *resource.Info) error {
 		options := metav1.PatchOptions{
 			Force: &o.ForceConflicts,
 		}
-		obj, err := helper.Patch(
+		obj, err := helper.
+			WithSubresource(o.Subresource).
+			Patch(
 				info.Namespace,
 				info.Name,
 				types.ApplyPatchType,

test/cmd/apply.sh

@@ -413,6 +413,10 @@ run_kubectl_server_side_apply_tests() {
   kubectl apply --server-side --field-manager=my-field-manager --force-conflicts -f hack/testdata/pod.yaml "${kube_flags[@]:?}"
   output_message=$(kubectl get -f hack/testdata/pod.yaml -o=jsonpath='{.metadata.managedFields[*].manager}' "${kube_flags[@]:?}" 2>&1)
   kube::test::if_has_string "${output_message}" 'my-field-manager'
+  # can add pod condition
+  kubectl apply --server-side --subresource=status --field-manager=my-field-manager -f hack/testdata/pod-apply-status.yaml "${kube_flags[@]:?}"
+  output_message=$(kubectl get -f hack/testdata/pod.yaml -o=jsonpath='{.status.conditions[*].type}' "${kube_flags[@]:?}" 2>&1)
+  kube::test::if_has_string "${output_message}" 'example.io/Foo'
   # Clean up
   kubectl delete pods test-pod "${kube_flags[@]:?}"