Add internal kubeadm output API

Added internal structures and APIs to handle
kubeadm structured output.

cmd/kubeadm/app/cmd/BUILD

@@ -84,6 +84,7 @@ go_test(
         "//cmd/kubeadm/app/features:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
         "//cmd/kubeadm/app/util/config:go_default_library",
+        "//cmd/kubeadm/app/util/output:go_default_library",
         "//cmd/kubeadm/app/util/runtime:go_default_library",
         "//staging/src/k8s.io/api/core/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library",

cmd/kubeadm/app/util/BUILD

@@ -84,6 +84,7 @@ filegroup(
         "//cmd/kubeadm/app/util/initsystem:all-srcs",
         "//cmd/kubeadm/app/util/kubeconfig:all-srcs",
         "//cmd/kubeadm/app/util/kustomize:all-srcs",
+        "//cmd/kubeadm/app/util/output:all-srcs",
         "//cmd/kubeadm/app/util/pkiutil:all-srcs",
         "//cmd/kubeadm/app/util/pubkeypin:all-srcs",
         "//cmd/kubeadm/app/util/runtime:all-srcs",

cmd/kubeadm/app/util/output/BUILD

@@ -0,0 +1,28 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["output.go"],
+    importpath = "k8s.io/kubernetes/cmd/kubeadm/app/util/output",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/cli-runtime/pkg/genericclioptions:go_default_library",
+        "//staging/src/k8s.io/cli-runtime/pkg/printers:go_default_library",
+        "//vendor/github.com/spf13/cobra:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

cmd/kubeadm/app/util/output/output.go

@@ -0,0 +1,192 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package output
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/spf13/cobra"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/cli-runtime/pkg/genericclioptions"
+	"k8s.io/cli-runtime/pkg/printers"
+)
+
+// TextOutput describes the plain text output
+const TextOutput = "text"
+
+// TextPrintFlags is an iterface to handle custom text output
+type TextPrintFlags interface {
+	ToPrinter(outputFormat string) (Printer, error)
+}
+
+// PrintFlags composes common printer flag structs
+// used across kubeadm commands, and provides a method
+// of retrieving a known printer based on flag values provided.
+type PrintFlags struct {
+	// JSONYamlPrintFlags provides default flags necessary for json/yaml printing.
+	JSONYamlPrintFlags *genericclioptions.JSONYamlPrintFlags
+	// KubeTemplatePrintFlags composes print flags that provide both a JSONPath and a go-template printer.
+	KubeTemplatePrintFlags *genericclioptions.KubeTemplatePrintFlags
+	// JSONYamlPrintFlags provides default flags necessary for kubeadm text printing.
+	TextPrintFlags TextPrintFlags
+	// TypeSetterPrinter is an implementation of ResourcePrinter that wraps another printer with types set on the objects
+	TypeSetterPrinter *printers.TypeSetterPrinter
+	// OutputFormat contains currently set output format
+	OutputFormat *string
+
+	// OutputFlagSpecified indicates whether the user specifically requested a certain kind of output.
+	// Using this function allows a sophisticated caller to change the flag binding logic if they so desire.
+	OutputFlagSpecified func() bool
+}
+
+// AllowedFormats returns list of allowed output formats
+func (pf *PrintFlags) AllowedFormats() []string {
+	ret := []string{TextOutput}
+	ret = append(ret, pf.JSONYamlPrintFlags.AllowedFormats()...)
+	ret = append(ret, pf.KubeTemplatePrintFlags.AllowedFormats()...)
+
+	return ret
+}
+
+// ToPrinter receives an outputFormat and returns a printer capable of
+// handling format printing.
+// Returns error if the specified outputFormat does not match supported formats.
+func (pf *PrintFlags) ToPrinter() (Printer, error) {
+	outputFormat := ""
+	if pf.OutputFormat != nil {
+		outputFormat = *pf.OutputFormat
+	}
+
+	if pf.TextPrintFlags != nil {
+		if p, err := pf.TextPrintFlags.ToPrinter(outputFormat); !genericclioptions.IsNoCompatiblePrinterError(err) {
+			return p, err
+		}
+	}
+
+	if pf.JSONYamlPrintFlags != nil {
+		if p, err := pf.JSONYamlPrintFlags.ToPrinter(outputFormat); !genericclioptions.IsNoCompatiblePrinterError(err) {
+			return NewResourcePrinterWrapper(pf.TypeSetterPrinter.WrapToPrinter(p, err))
+		}
+	}
+
+	if pf.KubeTemplatePrintFlags != nil {
+		if p, err := pf.KubeTemplatePrintFlags.ToPrinter(outputFormat); !genericclioptions.IsNoCompatiblePrinterError(err) {
+			return NewResourcePrinterWrapper(pf.TypeSetterPrinter.WrapToPrinter(p, err))
+		}
+	}
+
+	return nil, genericclioptions.NoCompatiblePrinterError{OutputFormat: pf.OutputFormat, AllowedFormats: pf.AllowedFormats()}
+}
+
+// AddFlags receives a *cobra.Command reference and binds
+// flags related to Kubeadm printing to it
+func (pf *PrintFlags) AddFlags(cmd *cobra.Command) {
+	pf.JSONYamlPrintFlags.AddFlags(cmd)
+	pf.KubeTemplatePrintFlags.AddFlags(cmd)
+	cmd.Flags().StringVarP(pf.OutputFormat, "experimental-output", "o", *pf.OutputFormat, fmt.Sprintf("Output format. One of: %s.", strings.Join(pf.AllowedFormats(), "|")))
+}
+
+// WithDefaultOutput sets a default output format if one is not provided through a flag value
+func (pf *PrintFlags) WithDefaultOutput(outputFormat string) *PrintFlags {
+	pf.OutputFormat = &outputFormat
+	return pf
+}
+
+// WithTypeSetter sets a wrapper than will surround the returned printer with a printer to type resources
+func (pf *PrintFlags) WithTypeSetter(scheme *runtime.Scheme) *PrintFlags {
+	pf.TypeSetterPrinter = printers.NewTypeSetter(scheme)
+	return pf
+}
+
+// NewOutputFlags creates new KubeadmOutputFlags
+func NewOutputFlags(textPrintFlags TextPrintFlags) *PrintFlags {
+	outputFormat := ""
+
+	pf := &PrintFlags{
+		OutputFormat: &outputFormat,
+
+		JSONYamlPrintFlags:     genericclioptions.NewJSONYamlPrintFlags(),
+		KubeTemplatePrintFlags: genericclioptions.NewKubeTemplatePrintFlags(),
+		TextPrintFlags:         textPrintFlags,
+	}
+
+	// disable deprecated --template option
+	pf.KubeTemplatePrintFlags.TemplateArgument = nil
+
+	return pf
+}
+
+// Printer is a common printing interface in Kubeadm
+type Printer interface {
+	PrintObj(obj runtime.Object, writer io.Writer) error
+	Fprintf(writer io.Writer, format string, args ...interface{}) (n int, err error)
+	Printf(format string, args ...interface{}) (n int, err error)
+}
+
+// TextPrinter implements Printer interface for generic text output
+type TextPrinter struct {
+}
+
+// PrintObj is an implementation of ResourcePrinter.PrintObj that prints object
+func (tp *TextPrinter) PrintObj(obj runtime.Object, writer io.Writer) error {
+	_, err := fmt.Fprintf(writer, "%+v\n", obj)
+	return err
+}
+
+// Fprintf is a wrapper around fmt.Fprintf
+func (tp *TextPrinter) Fprintf(writer io.Writer, format string, args ...interface{}) (n int, err error) {
+	return fmt.Fprintf(writer, format, args...)
+}
+
+// Printf is a wrapper around fmt.Printf
+func (tp *TextPrinter) Printf(format string, args ...interface{}) (n int, err error) {
+	return fmt.Printf(format, args...)
+}
+
+// ResourcePrinterWrapper wraps ResourcePrinter and implements Printer interface
+type ResourcePrinterWrapper struct {
+	Printer printers.ResourcePrinter
+}
+
+// NewResourcePrinterWrapper creates new ResourcePrinter object
+func NewResourcePrinterWrapper(resourcePrinter printers.ResourcePrinter, err error) (Printer, error) {
+	if err != nil {
+		return nil, err
+	}
+	return &ResourcePrinterWrapper{Printer: resourcePrinter}, nil
+}
+
+// PrintObj is an implementation of ResourcePrinter.PrintObj that calls underlying printer API
+func (rpw *ResourcePrinterWrapper) PrintObj(obj runtime.Object, writer io.Writer) error {
+	return rpw.Printer.PrintObj(obj, writer)
+}
+
+// Fprintf is an empty method to satisfy Printer interface
+// and silent info printing for structured output
+// This method is usually redefined for the text output
+func (rpw *ResourcePrinterWrapper) Fprintf(writer io.Writer, format string, args ...interface{}) (n int, err error) {
+	return 0, nil
+}
+
+// Printf is an empty method to satisfy Printer interface
+// and silent info printing for structured output
+// This method is usually redefined for the text output
+func (rpw *ResourcePrinterWrapper) Printf(format string, args ...interface{}) (n int, err error) {
+	return 0, nil
+}