Dig golang function reflect.DeepEqual when we need to check json struct is equal

main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"reflect"
	"unsafe"

	log "github.com/Sirupsen/logrus"
)

type visit struct {
	a1  unsafe.Pointer
	a2  unsafe.Pointer
	typ reflect.Type
}

// the function is copy from reflect
func deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool, depth int) bool {
	if !v1.IsValid() || !v2.IsValid() {
		return v1.IsValid() == v2.IsValid()
	}
	if v1.Type() != v2.Type() {
		return false
	}

	// if depth > 10 { panic("deepValueEqual") }	// for debugging

	// We want to avoid putting more in the visited map than we need to.
	// For any possible reference cycle that might be encountered,
	// hard(t) needs to return true for at least one of the types in the cycle.
	hard := func(k reflect.Kind) bool {
		switch k {
		case reflect.Map, reflect.Slice, reflect.Ptr, reflect.Interface:
			return true
		}
		return false
	}

	if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) {
		addr1 := unsafe.Pointer(v1.UnsafeAddr())
		addr2 := unsafe.Pointer(v2.UnsafeAddr())
		if uintptr(addr1) > uintptr(addr2) {
			// Canonicalize order to reduce number of entries in visited.
			// Assumes non-moving garbage collector.
			addr1, addr2 = addr2, addr1
		}

		// Short circuit if references are already seen.
		typ := v1.Type()
		v := visit{addr1, addr2, typ}
		if visited[v] {
			return true
		}

		// Remember for later.
		visited[v] = true
	}

	switch v1.Kind() {
	case reflect.Array:
		for i := 0; i < v1.Len(); i++ {
			if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
				return false
			}
		}
		return true
	case reflect.Slice:
		if v1.IsNil() != v2.IsNil() {
			fmt.Println("content :", v1, "type :", v1.Kind(), "isNil :", v1.IsNil())
			fmt.Println("content :", v2, "type :", v2.Kind(), "isNil :", v2.IsNil())
			return false
		}
		if v1.Len() != v2.Len() {
			return false
		}
		if v1.Pointer() == v2.Pointer() {
			return true
		}
		for i := 0; i < v1.Len(); i++ {
			if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
				return false
			}
		}
		return true
	case reflect.Interface:
		if v1.IsNil() || v2.IsNil() {
			return v1.IsNil() == v2.IsNil()
		}
		return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
	case reflect.Ptr:
		if v1.Pointer() == v2.Pointer() {
			return true
		}
		return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
	case reflect.Struct:
		for i, n := 0, v1.NumField(); i < n; i++ {
			if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {
				return false
			}
		}
		return true
	case reflect.Map:
		if v1.IsNil() != v2.IsNil() {
			return false
		}
		if v1.Len() != v2.Len() {
			return false
		}
		if v1.Pointer() == v2.Pointer() {
			return true
		}
		for _, k := range v1.MapKeys() {
			val1 := v1.MapIndex(k)
			val2 := v2.MapIndex(k)
			if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
				return false
			}
		}
		return true
	case reflect.Func:
		if v1.IsNil() && v2.IsNil() {
			return true
		}
		// Can't do better than this:
		return false
	default:
		// Normal equality suffices
		return false //valueInterface(v1, false) == valueInterface(v2, false)
	}
}

type ACLResponse struct {
	Blacklist []string "`json:blacklist`"
	Whitelist []string "`json:whitelist`"
}

func (aclRes ACLResponse) blacklistString() string {
	return aclRes.toString(aclRes.Blacklist)
}

func (aclRes ACLResponse) whitelistString() string {
	return aclRes.toString(aclRes.Whitelist)
}

func (aclRes ACLResponse) toString(list []string) string {
	result := "[]"
	if len(list) > 0 {
		if listBytes, err := json.Marshal(list); err != nil {
			log.Warningf("Failed to marshal blacklist: %v", err)
		} else {
			result = string(listBytes)
		}
	}
	return result
}

func fetchACLFrom(url string) (ACLResponse, error) {
	acl := ACLResponse{}

	resp, err := http.Get(url)
	if err != nil {
		return acl, err
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return acl, err
	}

	err = json.Unmarshal(body, &acl)
	if err != nil {
		return acl, err
	}

	return acl, nil
}

func main() {
	result, err := fetchACLFrom("https://s3-ap-northeast-1.amazonaws.com/daidoujiminecraft/Daidouji/man_js_test/OnlyWhiteList.json")
	if err != nil {
		log.Fatalf("Failed to read json file: %v", err)
	}
	fmt.Println("Fetch JSON : { \"whitelist\": [\"hello\", \"world\"] }")

	checkFail := ACLResponse{Blacklist: []string{}, Whitelist: []string{"hello", "world"}}
	fmt.Println("If we set both Blacklist and Whitelist")
	fmt.Println("reflect.DeepEqual will return :", reflect.DeepEqual(result, checkFail))
	if !reflect.DeepEqual(result, checkFail) {
		fmt.Println("deepValueEqual Result :", deepValueEqual(reflect.ValueOf(result), reflect.ValueOf(checkFail), make(map[visit]bool), 0))
	}

	fmt.Println("Press any key to continue...")
	var input string
	fmt.Scanln(&input)

	checkPass := ACLResponse{Whitelist: []string{"hello", "world"}}
	fmt.Println("If we only set Whitelist")
	fmt.Println("reflect.DeepEqual will return :", reflect.DeepEqual(result, checkPass))
}