client-go: change jsonpath output of non-primitive types from Go-syntax to JSON

kubectl: add --output jsonpath-as-json to print a json array of results
kubeadm: fix test case using jsonpath result of non-primitive type

Kubernetes-commit: ba386aba4fe02906089ca3e96ee07925bced5d4d

util/jsonpath/jsonpath.go

@@ -18,6 +18,7 @@ package jsonpath
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
 	"reflect"
@@ -36,6 +37,7 @@ type JSONPath struct {
 	lastEndNode *Node
 
 	allowMissingKeys bool
+	outputJSON       bool
 }
 
 // New creates a new JSONPath with the given name.
@@ -125,10 +127,49 @@ func (j *JSONPath) FindResults(data interface{}) ([][]reflect.Value, error) {
 	return fullResult, nil
 }
 
+// EnableJSONOutput changes the PrintResults behavior to return a JSON array of results
+func (j *JSONPath) EnableJSONOutput(v bool) {
+	j.outputJSON = v
+}
+
 // PrintResults writes the results into writer
 func (j *JSONPath) PrintResults(wr io.Writer, results []reflect.Value) error {
+	if j.outputJSON {
+		// convert the []reflect.Value to something that json
+		// will be able to marshal
+		r := make([]interface{}, 0, len(results))
+		for i := range results {
+			r = append(r, results[i].Interface())
+		}
+		results = []reflect.Value{reflect.ValueOf(r)}
+	}
 	for i, r := range results {
-		text, err := j.evalToText(r)
+		var text []byte
+		var err error
+		outputJSON := true
+		kind := r.Kind()
+		if kind == reflect.Interface {
+			kind = r.Elem().Kind()
+		}
+		switch kind {
+		case reflect.Map:
+		case reflect.Array:
+		case reflect.Slice:
+		case reflect.Struct:
+		default:
+			outputJSON = false
+		}
+		switch {
+		case outputJSON || j.outputJSON:
+			if j.outputJSON {
+				text, err = json.MarshalIndent(r.Interface(), "", "    ")
+				text = append(text, '\n')
+			} else {
+				text, err = json.Marshal(r.Interface())
+			}
+		default:
+			text, err = j.evalToText(r)
+		}
 		if err != nil {
 			return err
 		}
@@ -139,7 +180,9 @@ func (j *JSONPath) PrintResults(wr io.Writer, results []reflect.Value) error {
 			return err
 		}
 	}
+
 	return nil
+
 }
 
 // walk visits tree rooted at the given node in DFS order