Golang Equal JSON Strings

README.md

JSON string equality

A little utility for testing if 2 json strings are equal, for use in tests.

Example

go run main.go '{"dog": 5, "cat": 3}' '{"cat":3, "dog": 5}'

Caveats

• You may want to use a matcher library (like gomega) that has a function for this, since some of the other functionality in those libraries is pretty awesome

equal_json.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"os"
	"reflect"
)

func AreEqualJSON(s1, s2 string) (bool, error) {
	var o1 interface{}
	var o2 interface{}

	var err error
	err = json.Unmarshal([]byte(s1), &o1)
	if err != nil {
		return false, fmt.Errorf("Error mashalling string 1 :: %s", err.Error())
	}
	err = json.Unmarshal([]byte(s2), &o2)
	if err != nil {
		return false, fmt.Errorf("Error mashalling string 2 :: %s", err.Error())
	}

	return reflect.DeepEqual(o1, o2), nil
}

func main() {
	flag.Parse()
	if len(flag.Args()) < 2 {
		fmt.Println("Need 2 arguments that are both json strings")
		os.Exit(1)
	}

	s1 := flag.Args()[0]
	s2 := flag.Args()[1]

	fmt.Println("s1:: ", s1)
	fmt.Println("s2:: ", s2)

	areEqual, err := AreEqualJSON(s1, s2)
	if err != nil {
		fmt.Println("Error mashalling strings", err.Error())
	}

	fmt.Println("Equal:: ", areEqual)
}

So the omega library uses this same approach:
https://github.com/onsi/gomega/blob/v1.0/matchers.go#L164
https://github.com/onsi/gomega/blob/v1.0/matchers/match_json_matcher.go#L15

The only difference is they marshall into an interface{} instead of a map[string]interface{} so they can handle arrays too.

I'm changing mine to use the same approach.

null, true, "abc" are also valid JSON. That's why interface{} should be used instead of map[string]interface{}.