golang-cz / nilslice

Golang: Recursively initialize all nil slices in a given object, so they json.Marshal() as empty array [] instead of null.

nilslice.Initialize(obj) - fix null arrays in JSON

Golang's json.Marshal() function has a very unfortunate behavior when encoding nil slices. It renders a null value in JSON instead of an empty array [].

This issue has a couple of open issues (ie. golang/go#27589) but none of the proposed solutions were accepted into the standard library as of Aug 2023.

This lightweight Go package will help you mitigate the issue by recursively initializing all nil slices in a given object using a reflect package.

type Payload struct {
	Items []Item `json:"items"`
}

payload := &Payload{}

b, _ := json.Marshal(payload)
fmt.Println(string(b))
// {"items": null}

b, _ = json.Marshal(nilslice.Initialize(payload))
fmt.Println(string(b))
// {"items": []}

Install

$ go get github.com/golang-cz/nilslice

import "github.com/golang-cz/nilslice"

Authors

• golang.cz

License

MIT license