Consider omitempty

[matheusfenolio]

Hello!

I just came across this library, and thought it would be a good one to do my first OSS contribution. 🙂

This proposal aims to implement the issue #2. I alter a little bit the internals, and simplified some things on the user end as well.

Below, I have posted a code example + the output

package main

import (
	"fmt"

	"github.com/snorwin/jsonpatch/jsonpatch"
)

type Complex struct {
	String string            `json:"string"`
	Bolean bool              `json:"boolean,omitempty"`
	Float  float64           `json:"float"`
	Uint   uint              `json:"uint"`
	Int    int               `json:"int"`
	Slice  []string          `json:"slice"`
	Map    map[string]string `json:"map"`
}

type Basic struct {
	Name    string  `json:"name"`
	Age     int     `json:"age,omitempty"`
	Complex Complex `json:"complex"`
}

func main() {
	base := Basic{Name: "Raul", Age: 10000, Complex: Complex{
		String: "a",
		Bolean: true,
		Float:  float64(1),
		Uint:   uint(1),
		Int:    int(1),
		Slice:  []string{"a"},
		Map:    map[string]string{"a": "a"},
	}}
	modified := Basic{Name: "Jhon", Complex: Complex{}}

	p, err := jsonpatch.CreateJSONPatch(modified, base)
	fmt.Println(p, err)
}

Output:

[
    {
        "op": "replace",
        "path": "/name",
        "value": "Jhon"
    },
    {
        "op": "remove",
        "path": "/age"
    },
    {
        "op": "replace",
        "path": "/complex/string",
        "value": ""
    },
    {
        "op": "remove",
        "path": "/complex/boolean"
    },
    {
        "op": "replace",
        "path": "/complex/float",
        "value": 0
    },
    {
        "op": "replace",
        "path": "/complex/uint",
        "value": 0
    },
    {
        "op": "replace",
        "path": "/complex/int",
        "value": 0
    },
    {
        "op": "remove",
        "path": "/complex/slice/0"
    },
    {
        "op": "remove",
        "path": "/complex/map/a"
    }
]

Also works with you flag the struct

[
    {
        "op": "replace",
        "path": "/name",
        "value": "Jhon"
    },
    {
        "op": "replace",
        "path": "/age",
        "value": 0
    },
    {
        "op": "remove",
        "path": "/complex"
    }
]

[snorwin]

@matheusfenolio can you please rebase this PR, I fixed the tests.