Get modified data from JSON documents

get_modified_data.go

package main

import (
	"encoding/json"

	jsonpatch "github.com/evanphx/json-patch"
	"github.com/pkg/errors"
	// "k8s.io/apimachinery/pkg/util/strategicpatch"
)


// getPatchData will return difference between original and modified document
func getPatchData(originalObj, modifiedObj interface{}) ([]byte, error) {
	originalData, err := json.Marshal(originalObj)
	if err != nil {
		return nil, errors.Wrapf(err, "failed marshal original data")
	}
	modifiedData, err := json.Marshal(modifiedObj)
	if err != nil {
		return nil, errors.Wrapf(err, "failed marshal original data")
	}

	// Using strategicpatch package can cause below error
	// Error: CreateTwoWayMergePatch failed: unable to find api field in struct Unstructured for the json field "spec"
	//patchBytes, err := strategicpatch.CreateTwoWayMergePatch(originalData, modifiedData, originalObj)
	// if err != nil {
	// 	return nil, errors.Errorf("CreateTwoWayMergePatch failed: %v", err)
	// }

	patchBytes, err := jsonpatch.CreateMergePatch(originalData, modifiedData)
	if err != nil {
		return nil, errors.Errorf("CreateTwoWayMergePatch failed: %v", err)
	}
	return patchBytes, nil
}