let type struct,array,slice also being considerred when sorting kubectl output

pkg/kubectl/sorting_printer.go

@@ -23,8 +23,10 @@ import (
 	"sort"
 
 	"k8s.io/kubernetes/pkg/api/meta"
+	"k8s.io/kubernetes/pkg/api/unversioned"
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/runtime"
+	"k8s.io/kubernetes/pkg/util/integer"
 	"k8s.io/kubernetes/pkg/util/jsonpath"
 
 	"github.com/golang/glog"
@@ -153,11 +155,56 @@ func isLess(i, j reflect.Value) (bool, error) {
 		return i.String() < j.String(), nil
 	case reflect.Ptr:
 		return isLess(i.Elem(), j.Elem())
+	case reflect.Struct:
+		// special case handling
+		lessFuncList := []structLessFunc{timeLess}
+		if ok, less := structLess(i, j, lessFuncList); ok {
+			return less, nil
+		}
+		// fallback to the fields comparision
+		for idx := 0; idx < i.NumField(); idx++ {
+			less, err := isLess(i.Field(idx), j.Field(idx))
+			if err != nil || !less {
+				return less, err
+			}
+		}
+		return true, nil
+	case reflect.Array, reflect.Slice:
+		// note: the length of i and j may be different
+		for idx := 0; idx < integer.IntMin(i.Len(), j.Len()); idx++ {
+			less, err := isLess(i.Index(idx), j.Index(idx))
+			if err != nil || !less {
+				return less, err
+			}
+		}
+		return true, nil
 	default:
 		return false, fmt.Errorf("unsortable type: %v", i.Kind())
 	}
 }
 
+// structLessFunc checks whether i and j could be compared(the first return value),
+// and if it could, return whether i is less than j(the second return value)
+type structLessFunc func(i, j reflect.Value) (bool, bool)
+
+// structLess returns whether i and j could be compared with the given function list
+func structLess(i, j reflect.Value, lessFuncList []structLessFunc) (bool, bool) {
+	for _, lessFunc := range lessFuncList {
+		if ok, less := lessFunc(i, j); ok {
+			return ok, less
+		}
+	}
+	return false, false
+}
+
+// compare two unversioned.Time values.
+func timeLess(i, j reflect.Value) (bool, bool) {
+	if i.Type() != reflect.TypeOf(unversioned.Unix(0, 0)) {
+		return false, false
+	}
+	return true, i.MethodByName("Before").Call([]reflect.Value{j})[0].Bool()
+}
+
 func (r *RuntimeSort) Less(i, j int) bool {
 	iObj := r.objs[i]
 	jObj := r.objs[j]