How to not marshal an empty struct into JSON with Go?

Question

I have a struct like this:

type Result struct {
    Data       MyStruct  `json:\"data,omitempty\"`
    Status     string    `json:\"status,omitempty\"`
    R         


        

Answer 1

There is an outstanding Golang proposal for this feature which has been active for over 4 years, so at this point, it is safe to assume that it will not make it into the standard library anytime soon. As @Matt pointed out, the traditional approach is to convert the structs to pointers-to-structs. If this approach is infeasible (or impractical), then an alternative is to use an alternate json encoder which does support omitting zero value structs.

I created a mirror of the Golang json library (clarketm/json) with added support for omitting zero value structs when the omitempty tag is applied. This library detects zeroness in a similar manner to the popular YAML encoder go-yaml by recursively checking the public struct fields.

e.g.

$ go get -u "github.com/clarketm/json"

import (
    "fmt"
    "github.com/clarketm/json" // drop-in replacement for `encoding/json`
)

type Result struct {
    Data   MyStruct `json:"data,omitempty"`
    Status string   `json:"status,omitempty"`
    Reason string   `json:"reason,omitempty"`
}

j, _ := json.Marshal(&Result{
    Status: "204",
    Reason: "No Content",
})

fmt.Println(string(j))

// Note: `data` is omitted from the resultant json.
{
  "status": "204"
  "reason": "No Content"
}