Add feature toggle for OpenAPI V3 apply in kubectl

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

@@ -288,7 +288,7 @@ func (flags *ApplyFlags) ToOptions(f cmdutil.Factory, cmd *cobra.Command, baseNa
 	openAPISchema, _ := f.OpenAPISchema()
 	var openAPIV3Root openapi3.Root
 	openAPIV3Client, err := f.OpenAPIV3Client()
-	if err == nil {
+	if err == nil && !cmdutil.OpenAPIV3Apply.IsDisabled() {
 		cachedOpenAPIV3Client := cachedopenapi.NewClient(openAPIV3Client)
 		openAPIV3Root = openapi3.NewRoot(cachedOpenAPIV3Client)
 	}

staging/src/k8s.io/kubectl/pkg/cmd/testing/util.go

@@ -195,3 +195,18 @@ func WithAlphaEnvs(features []cmdutil.FeatureGate, t *testing.T, f func(*testing
 	}
 	f(t)
 }
+
+// WithAlphaEnvs calls func f with the given env-var-based feature gates disabled,
+// and then restores the original values of those variables.
+func WithAlphaEnvsDisabled(features []cmdutil.FeatureGate, t *testing.T, f func(*testing.T)) {
+	for _, feature := range features {
+		key := string(feature)
+		if key != "" {
+			oldValue := os.Getenv(key)
+			err := os.Setenv(key, "false")
+			require.NoError(t, err, "unexpected error setting alpha env")
+			defer os.Setenv(key, oldValue)
+		}
+	}
+	f(t)
+}

staging/src/k8s.io/kubectl/pkg/cmd/util/helpers.go

@@ -428,6 +428,7 @@ const (
 	ApplySet                FeatureGate = "KUBECTL_APPLYSET"
 	CmdPluginAsSubcommand   FeatureGate = "KUBECTL_ENABLE_CMD_SHADOW"
 	InteractiveDelete       FeatureGate = "KUBECTL_INTERACTIVE_DELETE"
+	OpenAPIV3Apply          FeatureGate = "KUBECTL_OPENAPIV3_APPLY"
 	RemoteCommandWebsockets FeatureGate = "KUBECTL_REMOTE_COMMAND_WEBSOCKETS"
 )